Determination of molybdenum isotope abundances and ratios for nuclear samples analysis using Thermal Ionization Mass Spectrometry

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The development of two separation protocols was undertaken in the absence of HCl, known to lead to issues in glove boxes conditions. The first one is the purification of Mo from Zr and Ru through the implementation of a single-stage separation process, utilizing the TEVA resin. The second one combines a separation using UTEVA and TEVA resins to purify Zr and Mo if both element isotope abundance must be analyzed. For both protocols, the recovery of the Mo was greater than 80%, and the decontamination factor of Mo in regard of Zr and Ru was greater than 700. The measurement of Mo isotope ratios on a purified Mo sample exhibited no statistically significant deviation from the reference values. The study of the main contributors to the isotope ratio uncertainties showed that: a reduction of the uncertainty of the certified value of the 98 Mo isotope abundance is needed to improve the accuracy of the measurement using the internal normalization and a better measurement repeatability is needed to improve the uncertainty of the isotope ratios corrected using an external normalization. Then, the developed protocols were then successfully applied to three nuclear samples. The relative uncertainties of the isotope abundances of the main isotopes were estimated to be less than 1%. Separation TIMS Molybdenum Uncertainty evaluation isotope ratio Figures Figure 1 Figure 2 Figure 3 1. Introduction Molybdenum (Mo) is classified as a transition metal and has seven naturally occurring stable isotopes ( 92 Mo, 94 Mo, 95 Mo, 96 Mo, 97 Mo, 98 Mo and 100 Mo). The analysis of its isotope ratios is interesting for the geochemistry, cosmochemistry, biochemistry and environmental studies [ 1 – 3 ]. Mo is also one of the major fission product [ 4 ]. The Mo fission product is characterized by the presence of four major isotopes ( 95 Mo, 97 Mo, 98 Mo and 100 Mo) [ 5 ]. It is found in all stages during the treatment and recycling of the nuclear spent fuel. It is one constituent of dissolution fines that can clog the dissolver during the dissolution process [ 6 ]. The accurate determination of its isotope composition helps to understand the nuclear processes. Its quantification can also be used to measure the spent fuel burn-up [ 5 ]. The Atalante facility of the French Alternative Energies and Atomic Energy Commission (CEA) is dedicated to the research and development on the backend of the fuel cycle and the reprocessing process of the spent nuclear fuel. The isotope analysis of Mo is an essential component of the research undertaken to enhance the characterization of nuclear spent fuel and dissolution fines. The isotope composition analysis of nuclear samples required specific installation (glove boxes, shieled lines) to be performed in safe condition. In the Atalante facility, only two instruments, able to perform isotopic measurement, are nuclearized ( i.e . modify to be used with radioactive sample): a simple quadrupole Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and a Thermal Ionization Mass Spectrometry (TIMS). TIMS can perform isotopic measurement with a greater accuracy than the quadrupole ICP-MS. Uncertainties below 1% can be obtained for a wide range of element [ 7 – 10 ]. Due to its high first ionization potential (7.1eV), the measurement of Mo + ion is difficult [ 3 ]. Only low signal can be obtained using the positive mode of the TIMS [ 1 ]. In other hand, it is now well established that its ionization efficacy is improved using the negative mode of the TIMS (N-TIMS) [ 1 – 3 , 11 , 12 ]. Its ionization is enhanced using an activator to form and detect the MoO 3 - species. Different activators with different proportion of lanthanum, calcium or gadolinium nitrate were previously tested by Nagai et Yokayama [ 3 ]: it was demonstrated that the optimal condition for Mo ionization is achieved when the Mo sample on the filament is covered by lanthanum nitrate, with a La/Mo ratio of 5. After correcting the oxygen isotopic interferences and the instrument isotope fractionation using an internal normalization, repeatabilities below 0.01% can be obtained on the Mo isotope ratios. To avoid isobaric interferences ( e.g . 96 Mo/ 96 Ru/ 96 Zr) and possible competition between element ionization during the evaporation process, a purification step of the Mo is required. Liquid/liquid extraction [ 13 ], High Performance Liquid Chromatography (HPLC) [ 5 ], chemical process [ 14 ] or solid phase extraction (SPE) [ 2 , 3 , 15 , 16 ] can be used to obtain a pure fraction of Mo. SPE is easy to use in glove boxes or in shielded lines. However, the SPE protocols developed in the literature requires several resin separations [ 2 , 3 , 15 , 16 ], a process that is time-consuming and results in an increase in the volume of radioactive effluents. Furthermore, the separation conditions require using HCl, that can be problematic when working in glove box condition. Indeed, to prevent the corrosion of the glove boxes, it is recommended to avoid it, whenever feasible. Radioactive effluent containing chlorine must also undergo treatment to comply with the relevant specifications prior to its evacuation. This paper presents an analytical procedure developed for the analysis of the Mo isotope ratios and isotope abundances using TIMS for nuclear samples. The development of two separation protocols without using HCl is reported herein. The initial protocol involves the combination of two distinct resins in the case of the analysis of both Mo and Zr isotope ratios. The second protocol uses a single resin for the purification of Mo. The TIMS results obtained on a standard solution will be discussed in terms of accuracy ( i.e. measurement trueness and precision) [ 17 , 18 ]. The evaluation of the uncertainties will be conducted to ascertain the primary contributor to global uncertainty. 2. Experimental Materials, reagents and samples All dilutions were performed using deionized water obtained from a Milli-Q system (resistivity: 18.2 MΩ cm, Millipore, Milford). Nitric acid (w = 67 − 70%, J.T. Baker) of Ultrex II reagent grade was used. Oxalic acid and lanthanum nitrate powder (purity > 99.999%) was purchased from Sigma Aldrich. All dilutions were performed volumetrically using pre-calibrated micropipettes. The Mo reference solution was the SRM 3134 provided by the National Institute of Standards and Technology (NIST). The reference value for the isotope abundance that was retained was the one designated by the International Union of Pure and Applied Chemistry (IUPAC) [ 19 , 20 ]. Zr and Ru were provided by Analytica as natural monoelement standard solutions at 1000 mg L -1 . A solution containing only Mo, hereafter referred to as ‘Mo solution” with a concentration of 50 mg L -1 was prepared from the SRM 3134. A second solution, hereafter referred to as ‘Mo/Zr/Ru solution”, with a concentration of 50 mg L -1 each was prepared from the monoelement solutions. 2 mL TEVA and UTEVA prepacked resins (Triskem, France) with 100–150 µm particle size were used in gravity mode according to different separation procedure. The flow- rate was estimated to approximatively 25 mL h -1 (v = 50 cm h -1 ). The developed methodology was applied to three samples, hereafter referred to as “sample 1, 2 and 3”, to determine the Mo isotope abundance. All experiments were performed in glove boxes to work with radioactive solutions in safe experimental conditions. These samples came from experiments performed in the Atalante facility. The samples 1 and 2 came from the dissolution of solid samples obtained during the reprocessing of spent nuclear fuel. The sample 3 came from the dissolution of the spent nuclear fuel, performed in a shielded line. Sample 1 and 2 are similar and are the most challenging in terms of separation: [Mo] ≈ 100 mg L -1 , [Zr] ≈ 1000 mg L -1 , [U + Pu] ≈ 10 mg L -1 , gamma activity = 5.10 8 Bq L -1 , the concentration of Ru was unknown. The characteristics of the sample 3 are: [Mo] ≈ 150 mg L -1 , [Ru] ≈ 1 mg L -1 , [Zr] ≈ 50 mg L -1 , [U + Pu] ≈ 400 mg L -1 , gamma activity = 3.10 9 Bq L -1 . In the laboratory, the gamma activity of the sample is limited to 5.10 8 Bq L -1 . Sample 3 was diluted 10-fold with 3 mol L -1 nitric acid in a shielded line before the transfer to the glove box laboratory. The sample received in the laboratory contained 15 mg L -1 of Mo. 5 mL of sample 1 and 2, and 1 mL of sample 3 were received in the laboratory. Separation procedure Two different separations protocols are proposed: (1) if only the Mo isotope abundance is required, the separation protocol is performed with a TEVA resin, and (2) if the Zr and the Mo isotope abundance is required, the separation protocol combines UTEVA and TEVA resin. The Zr purification is obtained after the UTEVA separation and the Mo purification is obtained after the TEVA separation. The experimental conditions for the Mo purification process are summarized in Table 1 . Table 1 UTEVA and TEVA resins separation protocol. Reagent Volume (mL) 1) UTEVA resin separation Conditioning 4 mol L − 1 HNO 3 4.5 Sample feeding 4 mol L − 1 HNO 3 1 Mo/Ru elution 4 mol L − 1 HNO 3 4.5 2) TEVA resin separation Conditioning 4 mol L − 1 HNO 3 / 0.2 mol L − 1 H 2 C 2 O 4 4.5 Sample feeding 4 mol L − 1 HNO 3 / 0.2 mol L − 1 H 2 C 2 O 4 1 Ru/Zr wash 4 mol L − 1 HNO 3 / 0.2 mol L − 1 H 2 C 2 O 4 18 Oxalic acid wash 1 mol L − 1 HNO 3 2.5 Mo elution 1 mol L − 1 HNO 3 4.5 If required the first step is the UTEVA separation. First, the HNO 3 concentration of the sample solution was adjusted to 4 mol L -1 . After conditioning the UTEVA resin with 4.5 mL of 4 mol L -1 HNO 3 , 1 mL of the sample solution was loaded onto the column. During this feeding step, Zr was fixed to the UTEVA resin. This step also helps to purify the Mo from U and Pu, which are the predominant elements in the nuclear samples, as they are fixed onto the resin [ 21 ]. Mo and Ru was eluted with 4.5 mL of 4 mol L -1 HNO 3 . Feeding and elution fractions containing Mo and Ru were collected and reunited to be evaporated and redissolved with a (1 mol L -1 /0.2 mol L -1 ) HNO 3 / H 2 C 2 O 4 mixture, to be in the optimal condition for the TEVA separation. If needed, the UTEVA resin is washed with 13.5 mL of 4 mol L -1 HNO 3 and the Zr is eluted with 4.5 mL of (4 mol L -1 /0.1 mol L -1 ) HNO 3 / H 2 C 2 O 4 mixture [ 6 ]. If the UTEVA separation protocol was not used prior, the first step of the TEVA separation is to adjust the acidity of the sample. For that, the sample is evaporated and redissolved with a (1 mol L -1 /0.2 mol L -1 ) HNO 3 / H 2 C 2 O 4 mixture. After conditioning the TEVA resin with 4.5 mL of (1 mol L -1 /0.2 mol L -1 ) HNO 3 / H 2 C 2 O 4 mixture, 1 mL of the solution was loaded onto the column. During this feeding step, the Mo was fixed to the TEVA resin. The Ru and the Zr, not retained by the resin, were wash with 18 mL of (1 mol L -1 /0.2 mol L -1 ) HNO 3 / H 2 C 2 O 4 mixture. This step helps also purifying the Mo from U and Pu, which are the predominant elements in the nuclear samples, as they are not retained by the resin. The column was washed with 2.5 mL of 1 mol L -1 HNO 3 , to avoid oxalic acid in the Mo elution solution. This volume was optimized to ensure that there was no loss of Mo during this step. Then, the Mo was eluted with 4.5 mL of 1 mol L -1 HNO 3 . This solution was evaporated and redissolved with 0.5 mol L -1 HNO 3 to obtain a Mo concentration of 1 µg µL -1 . ICP-OES and ICP-MS Elution fractions were analyzed by Inductively Coupled Plasma – Optical Emission Spectrometry (ICP-OES) to measure separation yield and decontamination factors. Analyses were performed using an Optima 8300 DV (Perkin Elmer) equipped with a micro-nebulizer and a small volume gutter cyclonic nebulization chamber. Each sample was diluted 10-fold with 0.5 mol L -1 HNO 3 before analyzing by ICP-OES. Scandium (1 mg L -1 ) was used as internal standard. It helps monitoring matrices effects but no correction was applied. The main operation conditions were: plasma power = 1300W, cooling gas flow rate = 15 L min -1 , outler gas flow rate = 0.2 L min -1 , nebulizer gas flow rate = 0.6 L min -1 , solution uptake rate = 1 mL min -1 and view mode = axial/radial. The wavelengths monitoring were 220.031, 203.845 and 204.597 nm for Mo, 361.383 nm for Sc, 257.139, 339.197, 343.823 and 354.262 nm for Zr and 240.272 and 349.894 nm for Ru. Results are expressed as the average of the concentration obtained on each individual wavelength. A single calibration standard was used. Limit of detections were determined by analyzing three blanks. Separation blanks were analyzed thanks to an Elan DRCe ICP-MS (Perkin Elmer) to ensure the separation procedure does not generate a Mo pollution. The main operation conditions were summarized in a previous study [ 22 ]. 115 In (1 µg L -1 ) was used as internal standard. The measured masses were 95 and 97 for the Mo determination and 115 for the internal standard. TIMS The measurements were performed on a Thermo Scientific Triton TIMS equipped with a glove box. The instrument is equipped with 9 Faraday cups (all are movables except the central denoted C) which are coupled to 10 11 Ω current amplifiers. 4 Faraday cups are positioned in low masses (noted L1–L4) and 4 Faraday cups are positioned in high masses (noted H1–H4). Sample loading The Mo isotopes were measured as MoO 3 - by N-TIMS. A single Re-filament configuration was used. These filaments (Re metal, purity 99.999%) are provided by ATES and were outgassed for 2h at 4.5 A in a high vacuum chamber (< 5 × 10 − 6 mbar) before use. The optimal time will be discussed in the results section. 1 µL of Mo sample solution (1 µg or 250 ng of Mo) was loaded onto the filament and dried at 0.4 A, then covered by 1 µL of La(NO 3 ) 3 solution (5 µg of La) as an activator, yielded a La/Mo ratio of 5 [ 1 – 3 ]. When the sample and the activator are completely dried, the filament is heated until a dull red color was observed. Measurement of Mo isotope ratios The sample filament was placed in the ion source. When the vacuum in the ion source is optimal (< 1.10 -7 mbar), the filament is heated to 2 A in 20 min. The gate valve that permits ions to access the sector flied is then opened. The evaporation filament is heated to obtain the major isotope ions beam of 10 mV. A “peak center” (mass calibration and ions beam centering in the detector) and the lenses optimization of the ion source are performed on the major isotope ion beam. The analysis is started when the major isotope ions beam reaches a minimum of 200 mV by heating the filament. The filament temperature was controlled to keep the ion beam intensity constant during the measurement, by increasing the current when necessary. Each measurement corresponded to 10 blocks of 10 cycles with an integration time of 8 s. Data processing When molybdenum is ionized in TIMS, it takes the form of MoO 3 - . However, the presence of oxygen results in isobaric interference due to the varying oxygen isotopes ( 16 O, 17 O and 18 O). The oxygen correction was previously detailed in the literature and are summarized in the Electronic Supplementary Information (ESI) [ 1 – 3 ]. The isotope fractionation was corrected thanks to the exponential law [ 23 ]. Two different normalizations were used: the internal and the external normalization [ 23 ]. For the isotope ratios measurement without separation, the measured ratios were corrected internally using the 98 Mo/ 96 Mo ratio (1.4568(19) [ 19 , 20 ]). Such normalization can’t be applied to samples with non-natural isotope abundance, as there is no known isotope ratio that can be considered as a reference ratio. All ratios measured after a separation step were corrected using an external normalization, even for the natural Mo, as the goal of this study is to measured three samples coming from the nuclear fuel cycle. The determination of the average normalization factor was achieved by measuring the 98 Mo/ 96 Mo ratio of the SRM 3134 several times: the mean of these measurement was 1.4549 with a standard deviation of 0.0053. To ensure the correction was accurate, the SRM 3134 was analyzed using the external normalization before and after each measurement series. Separation tests and TIMS experiments To guarantee the efficacy of the TIMS measurement, the SRM 3134 was measured 11 times without separation in 4 distinct measurement series. The mean of the eleven 98 Mo/ 96 Mo measured ratio lead to the determination of the isotope fractionation correction factor used for the external normalization. To verify the instrument and the reliability of the isotope fractionation correction factor, the SRM 3134 was measured before and after each measurement series involving samples that had undergone a separation. A total of 10 measurements were conducted on a deposit of 1 µg, while 5 measurements were performed on a deposit of 250 ng. Different deposits were analyzed to estimate the impact of a pollution of Zr and/or Ru on the Mo measurements: 3 deposits of Mo and Zr with m(Zr)/m(Mo) = 1, 3 deposits of Mo and Ru with m(Ru)/m(Mo) = 1, 2 deposits of Mo and Zr with m(Zr)/m(Mo) = 10 and 2 deposits of Mo, Zr and Ru with a 1/1/1 ratio. The first step for the separation development helped determining the volume of 1 mol L -1 HNO 3 for washing the oxalic acid for the TEVA column, which was used for the elution of the Ru and the Zr, without the elution the Mo. TEVA separation were performed on the Mo solution. The 1 mol L -1 HNO 3 was added in several small volumes, after which the elution fractions were measured by ICP-OES to determine the Mo recovery yield in each fraction. The experiments were reproduced 2 times. Then, the TEVA protocol (with the appropriate volume of 1 mol L -1 HNO 3 previously determined to wash the oxalic acid) was used on the Mo solution. The different fractions were measured by ICP-OES to determine the Mo recovery yield in each of them. The TEVA protocol was used on the Mo/Zr/Ru solution to demonstrate the Mo purification. The UTEVA + TEVA protocol were used on the Mo/Zr/Ru solution to demonstrate the Mo purification and its effect on the measurement of isotope ratios. All separation experiments were reproduced 3 times. The different elution fractions were measured by ICP-OES to determine the cation recovery yield in each fraction and the associated decontamination factor. The Mo elution fractions were measured by TIMS. Two deposits for each separation were performed, totaling six results. Chemical blanks were also prepared for the UTEVA and TEVA separation protocol: they consist in performing a separation using 1 mol L -1 HNO 3 and 4 mol L -1 HNO 3 / 0.2 mol L -1 H 2 C 2 O 4 , respectively, as a loading solution instead of the Mo/Zr/Ru solution to demonstrate the absence of these cations in the reactants and resins. The Mo fractions were measured by ICP-MS. The experiments were reproduced 3 times. The UTEVA + TEVA protocol was used on samples 1 and 2 as the Zr isotope composition was needed. The Mo elution fractions were measured by TIMS. The experiments were reproduced 3 times for each sample. Two deposits for each separation were performed, yielding a total of six results. For sample 3, the TEVA protocol was used as only the Mo isotope composition was required. The sample volume and the Mo quantity being limited for this sample, minor adjustments were made to the protocol: (1) the experiments were reproduced twice instead of three times. (2) The Mo concentration loaded on the column was about 7 mg L -1 instead of 50 mg L -1 . (3) The Mo quantity deposited in the filament was 250 ng instead of 1 µg (the activator quantity was adapted to ensure a La/Mo ratio of 5). (4) Each separation was measured three times by TIMS instead of two (totaling of six results). Results evaluation and uncertainties estimation The cations (Mo, Zr or Ru) separation performances were estimated using the recovery yield (RY, Eq. ( 1 )). $$\:RY\left(cation\right)\:\left(\text{%}\right)=\frac{{\left[cation\right]}_{after\:sep}}{{\left[cation\right]}_{before\:sep}}\bullet\:\frac{{V}_{elution}}{{V}_{loading}}$$ 1 Where [cation] after sep and [cation] before sep are the Mo, Zr or Ru concentration after and before separation, respectively, and V is the volume of solution. The decontamination factors of Mo in regard of Zr (DF(Mo/Zr)) and Ru (DF(Mo/Ru) were used to evaluate the purity of the recovered fractions (Eq. ( 2 )). An increase in the DF results in enhanced separation efficiency. $$\:DF(Mo/Zr\:or\:Ru)\:\left(\text{%}\right)=\frac{RY\left(Mo\right)}{RY\left(Zr\:or\:Ru\right)}$$ 2 The efficiency of the separation process was determined by the following criteria: a Mo recovery yield falling in the range of 80–120% and a DF greater than 100. Bias, or trueness, was calculated using Eq. ( 3 ). $$\:Bias\:\left(\text{%}\right)=\frac{\stackrel{-}{x}\:-ref}{ref}$$ 3 Where \(\:\stackrel{-}{x}\) is the mean of the measurement series and ref is the reference value [ 19 , 20 ]. Eq. ( 4 ) was used to determine whether the mean of the measurement series has a statistically significant bias compare to reference values. If the zeta-score is lower than 2, the final mean value is considered to have no statistically significant bias. If the zeta-score is between 2 and 3, the accuracy of the final mean value is questionable. If the zeta-score is higher than 3, the final mean value is considered having a statistically significant bias. $$\:\text{Z}\text{e}\text{t}\text{a}-\text{s}\text{c}\text{o}\text{r}\text{e}=\frac{\left|\stackrel{-}{x}-ref\right|}{\sqrt{{u}^{2}\left(\stackrel{-}{x}\right)+{u}^{2}\left(ref\right)}}$$ 4 with \(\:u\left(\stackrel{-}{x}\right)\) being the standard uncertainty of the mean of the measurement series and u(ref) the reference value standard uncertainty. The uncertainties were estimated using a bottom-up approach by taking into account all conceivable sources of uncertainty to be assessed [ 24 ]: reference value uncertainty for the determination of the fractionation factor, oxygen isotope ratio, collected intensities, inter-calibration gain, baseline, etc. The uncertainties were estimated using the Monte Carlo Method (MCM), as recommended in the supplement 1 of the Guide to the Expression of Uncertainty in Measurement (GUM) [ 24 ]. The uncertainty budget was established using the sensitivity indices (Sobol indices) [ 25 ]. All the calculations were made using R software (free of use) [ 26 ]. 3. Results and discussion TIMS measurement conditions The results of the TIMS measurement for the 95 Mo/ 95 Mo isotope ratio are illustrated in Fig. 1 . The full set of results can be found in Tables S3 to S10 in the ESI. Blank of filament Filaments blanks were analyzed with and without activator in two ways: first, without outgassing, and then after outgassing for 20 minutes and 2 hours. Without outgassing, the total signal from all the Mo isotopes was about 10 mV, and correspond to natural Mo. When the filaments were outgassed 20 min, the total signal from all the isotopes decreased compared to non-degassed filaments and was about 4 mV. For filaments outgassed 2h, no signal was observed except for one filament where a small signal was observed: the total signal from all the Mo isotopes was about 0.5 mV for the first 50 integrations. After that the signal was below the detection limit of the Faraday cup. This signal is small and negligible compared to the measured signal of the sample (> 200 mV). For the rest of this study, only filaments outgassed for 2h were used. Measurement of the SRM 3134 using internal normalization The data acquired on the SRM 3134 without separation using the internal normalization were compared to the reference value (Fig. 1 and Table S2 in the ESI). The RSD values were found to be less than 0.02% and a bias below 0.04% were observed for all isotope ratios. The relative expanded uncertainties were estimated to be less than 0.1% for the 95 Mo/ 96 Mo and 97 Mo/ 96 Mo ratios, and between 0.1% and 0.3% for the remaining isotope ratios. As demonstrated by the zeta-scores falling below 2, no statistically significant biases were identified when compared to reference values. Measurement of the SRM 3134 using external normalization The data acquired for a deposit of 1µg of the SRM 3134 without separation using the external normalization, analyzed before and after each separation series, were compared to the reference value (Fig. 1 and Table S3 in the ESI). The repeatabilities (between 0.08% and 0.4%) and the uncertainties (between 0.3% and 1.5%) were higher than the ones determined using the internal normalization. No statistically significant biases were identified in comparison to the reference value (zeta-scores below 2). These data obtained using the internal and external normalization help guarantying the reliability of the measurement results. For a deposit of 250ng, the zeta-scores below 2 confirms the accuracy of the results for this deposited amount (Fig. 1 and Table S4 in the ESI). Measurement of Mo, Zr and Ru mixtures without separation The results obtained for the Zr/Mo and Ru/Mo mixtures with a mass ratio of 1 showed no difference compared to the reference values (zeta-score below 2): the RSD (below 0.015%), the biases (below 0.05%) and the estimated uncertainties were similar compared to the values obtained for a pure Mo solution (Fig. 1 and Table S5 in the ESI). It appears that Zr and Ru do not form the ZrO 3 - and RuO 3 - species whit the La(NO 3 ) 3 activator. No differences were observed during the analyses of the Zr/Mo mixture compared to the pure Mo solution: the Mo analyses were performed with a filament current between 2100 and 2400 mA. The analyses of the Ru/Mo mixtures exhibited slight variations. The analyses were performed at higher temperature: the filament currents were between 2500 and 2900 mA. Moreover, for two deposits, only 60 and 70 measurement cycles could be taken. It hypothesized that the presence of Ru functions as an inhibitor of Mo evaporation and ionization. For Zr/Mo solutions with a mass ratio of 10, corresponding to the ratio in samples 1 and 2, the analyses were difficult. Only one deposit was analyzed as no signal was observed for the second. Only 60 cycles were measured. The total signal from all the isotopes was about 180 mV, which is less than the 2 V obtained for a pure Mo solution. The results showed no statistical differences compared to the reference values (zeta-score below 2). For the Mo/Ru/Zr solution, only one deposit was analyzed. No signal was observed for the second deposit. Only 80 measurement cycles were obtained with a filament current ranging from 2500 to 2950 mA. However, the results showed no statistical differences compare to the reference values (zeta-score below 2). The biases (below 0.1%) and the estimated uncertainties are comparable to the ones obtained for a pure Mo solution. Although the results for the Mo/Zr/Ru mixtures were in agreement with the reference values, a separation step is required to maximize the Mo signal and to avoid having to reanalyze a sample in the event of no signal. The analyses of mixtures demonstrated a high failure rate. Nevertheless, the results showed a minor contamination of the Mo fraction by Ru or Zr will exert an insignificant influence on the measurement of Mo isotope ratios. Optimization of the oxalic acid washing of the TEVA separation The first separation tests were performed using no oxalic acid wash: i.e . the Mo was eluted with 4.5 mL of nitric acid directly after the Zr/Ru elution. During the concentration step, prior to its deposition on the filament, the solution must be evaporated to dryness. This will result in the appearance of a white crystal, thereby rendering its redissolution with a small acid volume difficult (Figure S1 in the ESI). Moreover, the TIMS deposit was not clean. To ensure the complete removal of residual oxalic acid, it is necessary to add a volume of nitric acid. This preparatory step is a prerequisite for the subsequent execution of the Mo elution process. The results for the optimization of the oxalic acid wash are summarized in Fig. 2 . Before 2.6 mL of nitric acid, the Mo was not detected. Mo was eluted from a volume of 2.6 mL and was recovered up to 4.7 mL. A volume of nitric acid of 2.5 mL was chosen for the oxalic acid wash. The Mo was then eluted with 4.5 mL of nitric acid. The analyses of three Mo solution by adding this oxalic acid wash confirmed the good recovery of Mo: recovery = 99.3% with an RSD of 1.3%. In the oxalic acid wash fraction, the Mo was not detected. The evaporation of the Mo fraction showed no white crystal, confirming the elimination of most of the oxalic acid (Figure S1 in the ESI). This helps to obtain a good concentration step and a clean deposit on the filament. The measured isotope ratios of the Mo solution after the TEVA separation, corrected using an external normalization, were in agreement with the reference values (zeta-score below 2 for all isotope ratios, Fig. 1 and Table S6 in the ESI). The repeatabilities (RSD between 0.10 and 0.53%) and the estimated relative uncertainties (between 0.3 and 1.5%) were similar to the one observed for the SRM 3134 solution without separation using the external normalization. TEVA separation on the Mo/Zr/Ru solutions The Mo, Zr and Ru recovery yields for the TEVA separation were showed in Table 2 . About 100% of the Zr was recovered in the sample loading and Ru/Zr elution fraction. The Ru was not entirety eluted in this fraction (about 65%). Ru has a complex chemistry. During the evaporation step before the sample loading, the Ru can be evaporated as RuO 4(g) . Mo, Ru or Zr were not found in the oxalic acid wash fraction. 101% of the Mo was recovered in the Mo elution fraction. In this fraction, Zr was below the detection limit of the ICP-OES and 0.2% of the Ru was recovered. The DF(Mo/Zr) was greater than 1000 and DF(Mo/Ru) was about 500, confirming the effective purification of Mo against Ru and Zr. Table 2 Elemental recovery (mean) and one standard deviation (SD) of Zr, Mo and Ru for the TEVA separation. Elution fraction Zr Mo Ru Mean SD Mean SD Mean SD Sample loading and Ru/Zr elution 1.151 0.018 0.035 0.008 0.648 0.050 Oxalic acid wash < 0.001 - < 0.001 - < 0.001 - Mo elution < 0.001 - 1.011 0.011 0.002 0.001 The measured isotope ratios of the Mo fraction were in agreement with the reference values (zeta-score below 2 for all isotope ratios, Fig. 1 and Table S7 in the ESI). The repeatabilities (RSD between 0.05 and 0.3%) and the estimated relative uncertainties (between 0.3 and 1.5%) were similar to the one observed for the SRM 3134 solution without separation using the external normalization. These measurements help confirming the efficacy of the Mo measurement after the separation of Mo/Zr/Ru solution. UTEVA + TEVA separation on the Mo/Zr/Ru solution The Mo, Zr and Ru recovery yields for the UTEVA + TEVA separation were showed in Table 3 . The first test was performed without any evaporation/redissolution prior to the UTEVA separation. During this separation step, Mo and Zr were coeluted: Zr and Mo recoveries are about 90% and 102%, respectively (test 1 in Table 3 ). The DF(Mo/Zr) was about 1.1. This effect has no impact on the Mo purification as the TEVA separation, which is performed after the UTEVA separation for Mo/Ru separation, helps to separate Mo and Zr. Table 3 Elemental recovery (mean) and one standard deviation (SD) of Zr, Mo and Ru for the UTEVA + TEVA separation. Elution fraction Test Zr Mo Ru Mean SD Mean SD Mean SD UTEVA separation Solution after evaporation and dissolution 1 2 - 0.985 - 0.004 - 1.054 - 0.092 - 1.020 - 00087 Sample loading and Mo/Ru elution 1 2 0.903 0.786 0.004 0.009 1.020 0.868 0.006 0.034 1.015 0.816 0.005 0.038 TEVA separation Solution after evaporation and dissolution 1 2 0.899 0.778 0.002 0.015 0.964 0.872 0.012 0.021 0.977 0.426 0.005 0.038 Sample loading and Ru/Zr elution 1 2 0.924 0.793 0.016 0.014 0.002 0.007 0.002 0.003 0.761 0.319 0.020 0.017 Oxalic acid wash 1 2 < 0.001 < 0.001 - - 0.001 0.005 0.001 0.001 0.004 0.002 0.001 0.001 Mo elution 1 2 < 0.001 < 0.001 - - 0.810 0.862 0.018 0.015 0.006 0.001 0.002 0.002 The behavior of Zr during the UTEVA separation process was found to be unexpected. This separation step is frequently performed in the laboratory for Zr isotope ratio analysis in complex samples [ 6 , 27 ]. During these analyses, the Zr was fixed in the UTEVA resin. The only discrepancy observed was in the step involving the addition of a small quantity of Al 3+ to neutralize the fluoride. Fluoride, a constituent of the standard, has been proven to complex with Zr, thereby impeding its retention to the UTEVA resin. Here, this step was not employed to avoid a coelution of Al and Mo. The presence of Al and Mo in the same fraction is problematic during the filament deposit. In a previous study, this Al addition step was also not performed during the separation of cationic impurities in uranium and plutonium matrices [ 22 ]. The solution, which must be separated, contained fluoride due to the dissolution protocol. During the separation step, about 84% of the Zr was retained into the UTEVA column, using a protocol analogous to the one that has been employed here. Different tests were performed to try to understand and fix this strange behavior. First, the protocol was applied without any modification (same UTEVA protocol, same solution, same eluent). As expected, Zr was still not retained in the UTEVA resin: the Zr recovery was about 107%. Then, the protocol was modified: same UTEVA protocol, new solution, new eluent. Zr was still not retained onto the resin (recovery = 109%), confirming there were no problem during the preparation of the solutions and the eluents. The hypothesis was formulated that the presence of fluoride would result in disrupting the Zr behavior in the resin. Consequently, an evaporation/dissolution step was incorporated prior to the UTEVA resin. During the evaporation, the fluoride was evaporated. The implementation of this additional step resulted in the recovery of only 2% of the Zr in the Mo fraction: the Zr was now fixed onto the resin. To consolidate the modification of the protocol, three UTEVA + TEVA separation protocols were applied on the Mo/Zr/Ru solution (test 2 in Table 3 ). The evaporation/redissolution step did not cause any loss of Mo, Ru or Zr. The recoveries after the evaporation/redissolution step were about 100% for the three elements. However, the Zr was still present in the Mo fraction during the UTEVA separation step (recovery about 80% with a standard deviation of about 1%). After the TEVA separation step, the Mo was well purified: the recovery of the Mo was about 86%, the DF(Mo/Zr) was greater than 800 and DF(Mo/Ru) was about 800, confirming the effective purification of Mo against Ru and Zr. Experiments were still in progress to understand the behavior of the Zr. The measured isotope ratios of the Mo fractions were in agreement with the reference values (zeta-score below 2 for all isotope ratios, Fig. 1 and Table S8 in the ESI). The repeatabilities (RSD between 0.05 and 0.3%) and the estimated relative uncertainties (between 0.3 and 1.5%) were similar to the one observed for the SRM 3134 solution with or without separation using the external normalization. These measurements helped to confirm the efficacy of the Mo measurement after the separation of Mo/Zr/Ru solution using a combination of the UTEVA and TEVA resins. Blanks of the separation The blanks of the TEVA and UTEVA separations showed a concentration in the Mo fraction of 160 ng L -1 with an RSD of 14% and 70 ng L -1 with an RSD of 38%, respectively. This corresponds to a Mo mass of about 720 fg and 310 fg present in the Mo fraction, respectively. Depending on the volume of liquid used during the evaporation/redissolution step prior to the sample deposit, the amount of Mo mass deposited onto the filament was estimated between 6 and 150 fg. This quantity is negligible in comparison to the quantity of sample deposited (1 µg, with the exception of sample 3, where 250 ng were deposited) on the filament. The Mo sample over the Mo pollution ratio is higher than 1700. Mo isotope abundance in three nuclear samples The results for the three samples are illustrated in Fig. 3 and are presented in Table S9 in the ESI. The isotope ratios are presented relative to the 95 Mo isotope, which is one of the four major isotopes, as the 96 Mo isotope, used by convention for natural Mo, is a minor isotope. The isotope abundances of the three samples are quite different from natural Mo one. The isotope abundances of the seven isotopes are very similar for natural Mo (between 9 and 25% [ 19 ]). For the three samples, 95 Mo, 97 Mo, 98 Mo and 100 Mo isotopes are the major isotopes with similar isotope abundance (about 25%). The 96 Mo isotopes has an isotope abundance about 1%. 92 Mo and 94 Mo isotopes were detected in minor proportion (below 0.3%). The isotope composition of samples 1 and 2 are similar, with a difference in the isotope composition of the four major isotopes of less than 0.2%. Given the observed similarity in the provenance of the samples, analogous isotope abundance are to be expected. The isotope abundance of sample 3 differs from samples 1 and 2, thereby confirming the different provenance of the samples. The measurement repeatabilities (RSD < 0.6%) observed for the 97 Mo/ 95 Mo, 98 Mo/ 95 Mo and 100 Mo/ 95 Mo major isotope ratio are similar to the ones observed for natural Mo. Finally, the relative uncertainties were estimated to be less than 1% for the isotope abundance of the four major isotope ratios. Uncertainty budget The uncertainty budget, estimated using the sensitivity indices, were illustrated in Table S9 in the ESI for the natural Mo and in the Table S10 in the ESI for the samples. Only two parameters contribute to the uncertainty of the SRM 3134 isotope ratios using the internal normalization. The main contributor (between 77 and 96%) is the certified value of the 98 Mo isotope abundance. The impact of the uncertainty of the 18 O/ 16 O isotope ratio is limited (less than 10% of the budget), with the exception of the 97 Mo/ 96 Mo isotope ratio, for which it accounts for 19%. The remaining parameters (gain, baseline, measured signal, 17 O/ 16 O, certified value of the 96 Mo isotope abundance) exert minimal influence on the global uncertainty (below 5% maximum). It is imperative that the uncertainties of the SRM 3134 isotope ratios are improved to enhance the reliability of the isotope ratios measured using internal normalization. Only one parameter contributes to the uncertainty of the isotope ratios of the SRM 3134 solution using the external normalization. It has been determined that a minimum of 95% of the global uncertainty is attributable to the uncertainty surrounding the measured 98 Mo/ 96 Mo ( R mes ), which is used for external normalization. The standard uncertainty of R mes was estimated to be 0.36%, which in turn limited the isotope ratios uncertainty. An improvement of the measurement repeatability for the determination of R mes is needed to improve the uncertainty of the isotope ratios corrected using an external normalization. The aforementioned conclusion can also be drawn in relation to the uncertainty surrounding the i Mo/ 95 Mo isotope ratios and the 96 Mo and i Mo abundances for the three samples (with i = 96, 97, 98 or 100). A minimum of 80% of the global uncertainty is linked to the uncertainty surrounding the measured 98 Mo/ 96 Mo ( R mes ), which is used for external normalization. For the two lower isotopes ratios ( 92 Mo/ 95 Mo and 94 Mo/ 95 Mo), the measured signals are low especially for the sample 3 where the measured signal for masses 140 and 142 are about 0.6 and 0.4 mV, respectively. The baselines become a significant contributing factor. 4. Conclusion This study aimed to develop a separation protocol combines with TIMS measurement to perform the molybdenum isotopic analysis of nuclear samples. Despite being possible accurate measurement of Mo polluted by Zr and Ru, purification of Mo is required to enhance the collected signal. It appears that the formation of ZrO 3 - and RuO 3 - is not possible under these conditions (Re mono filament and La(NO 3 ) 3 activator). The protocol was first developed and tested on simulated solutions. The optimization of the TEVA protocol helped to limit the presence of oxalic acid in the Mo fraction and improved the implementation of the TIMS deposit. Separation protocols were found to be effective with recovery yields between 80 and 120%. The decontamination factor of Mo in regard of Zr and Ru was excellent and largely greater than 100. However, the understanding surprising behavior of Zr in the UTEVA is still in progress. The developed protocols were applied to analyze three nuclear samples. Significant differences were observed between the samples derived from distinct fuels, linked to their different burn-up profiles. The relative uncertainties in the isotope abundances of the main isotopes were estimated to be less than 1%, which is in agreement with the specifications of the project. To improve these uncertainties, an improvement of the isotope fractionation factor uncertainty is required. This can only be done by improving the repeatability of the uncorrected isotope ratio used to calculate the isotope fractionation factor by developing new TIMS methods. It would also be interesting to decrease the analyzable quantity to measure small quantity of Mo. For example, the samples received in the laboratory after the dissolution of transmutation discs contains only a few dozen of ng of Mo. Declarations Author Contribution Alexandre Quemet: Conceptualization, Investigation, Methodology, Writing - Original Draft, Supervision Luna Borchi: Investigation, Methodology Erwan Hamon: Investigation, Methodology Christophe Maillard: Methodology Acknowledgement The authors are grateful to Sarah Baghdadi (CEA/ MAR/DES/DMRC/SASP/LAAT) for its technical help and advice on the present paper and to Vincent Dalier (CEA/ MAR/DES/DMRC/SASP/LAAT), Sophie Gracia, Angélique Gaïdo and Xavier Heres (CEA/MAR/DES/DMRC/SPTC/LCIS) for their help with ICP MS and ICP OES measurements. References Song P, Wang J, Zhang Y, Lu H, Ren T (2019) Total evaporation technique for high-accuracy isotopic analysis of isotopically enriched molybdenum by negative thermal ionization mass spectrometry. Metrologia 56:024005. https://doi.org/10.1088/1681-7575/ab0a11 Yobregat E, Fitoussi C, Pili E, Touboul M (2022) High-precision measurements of Mo isotopes by N-TIMS. Int J Mass Spectrom 476:116846. https://doi.org/10.1016/j.ijms.2022.116846 Nagai Y, Yokoyama T (2016) Molybdenum isotopic analysis by negative thermal ionization mass spectrometry (N-TIMS): effects on oxygen isotopic composition. J Anal Spectrom 31:948–960. https://doi.org/10.1039/C5JA00381D Cuninghame JG (1957) The mass-yield curve for fission of natural uranium by 14-MeV neutrons. J Inorg Nucl Chem 5:1–5. https://doi.org/10.1016/0022-1902(57)80074-8 Bera S, Sujatha K, Sivaraman N, Narasimhan TSL (2019) Molybdenum and lanthanum as alternate burn-up monitors-development of chromatographic and mass spectrometric methods for determination of atom percent fission. Radiochim Acta 107:685–694. https://doi.org/10.1515/ract-2018-3017 Quemet A, Maillard C, Ruas A (2015) Determination of zirconium isotope composition and concentration for nuclear sample analysis using Thermal Ionization Mass Spectrometry. Int J Mass Spectrom 392:34–40. https://doi.org/10.1016/j.ijms.2015.08.023 Quemet A, Ruas A, Dalier V, Rivier C (2018) Americium isotope analysis by Thermal Ionization Mass Spectrometry using the Total Evaporation Method. Int J Mass Spectrom 431:8–14. https://doi.org/10.1016/j.ijms.2018.05.017 Quemet A, Ruas A, Dalier V, Rivier C (2019) Development and comparison of high accuracy thermal ionization methods for uranium isotope ratios determination in nuclear fuel. Int J Mass Spectrom 438:166–174. https://doi.org/10.1016/j.ijms.2019.01.008 Quemet A, Buravand E, Peres J-G, Dalier V, Bejaoui S (2022) Irradiated UAmO2 transmutation discs analyses: from dissolution to isotopic analyses. J Radioanal Nucl Chem 331:1051–1061. https://doi.org/10.1007/s10967-021-08156-2 Quemet A, Lasnier G, Mialle S, Isnard H, Boyet M, Garçon M, Auclair D (2024) Reference value of the JNdi-1 isotopic material without normalization. J Anal Spectrom 39:2165–2172. https://doi.org/10.1039/D4JA00140K Worsham EA, Walker RJ, Bermingham KR (2016) High-precision molybdenum isotope analysis by negative thermal ionization mass spectrometry. Int J Mass Spectrom 407:51–61. https://doi.org/10.1016/j.ijms.2016.06.005 Heumann KG, Eisenhut S, Gallus S, Hebeda EH, Nusko R, Vengosh A, Walczyk T (1995) Recent developments in thermal ionization mass spectrometric techniques for isotope analysis. A review. Analyst 120:1291. https://doi.org/10.1039/an9952001291 Tkac P, Paulenova A (2008) Speciation of Molybdenum (VI) In Aqueous and Organic Phases of Selected Extraction Systems. Sep Sci Technol 43:2641–2657. https://doi.org/10.1080/01496390802122261 Rao A, Kumar Sharma A, Kumar P, Charyulu MM, Tomar BS, Ramakumar KL (2014) Studies on separation and purification of fission 99Mo from neutron activated uranium aluminum alloy. Appl Radiat Isot 89:186–191. https://doi.org/10.1016/j.apradiso.2014.02.013 Migeon V, Bourdon B, Pili E, Fitoussi C (2015) An enhanced method for molybdenum separation and isotopic determination in uranium-rich materials and geological samples. J Anal Spectrom 30:1988–1996. https://doi.org/10.1039/C5JA00106D Nagai Y, Yokoyama T (2014) Chemical Separation of Mo and W from Terrestrial and Extraterrestrial Samples via Anion Exchange Chromatography. Anal Chem 86:4856–4863. https://doi.org/10.1021/ac404223t BIPM (2008) International vocalulary of metrology - Basic and general concepts and associated terms (VIM) 3rd edition ISO 5725-1:2023, Accuracy (trueness and precision) of measurement methods and results — Part 1: General principles and definitions Meija J, Coplen TB, Berglund M, Brand WA, De Bièvre P, Gröning M, Holden NE, Irrgeher J, Loss RD, Walczyk T, Prohaska T (2016) Isotopic compositions of the elements 2013 (IUPAC Technical Report). Pure Appl Chem 88:293–306. https://doi.org/10.1515/pac-2015-0503 Mayer AJ, Wieser ME (2014) The absolute isotopic composition and atomic weight of molybdenum in SRM 3134 using an isotopic double-spike. J Anal Spectrom 29:85–94. https://doi.org/10.1039/c3ja50164g Maillard C, Maloubier D, Boulay O, Savigny V, Quemet A (2021) U and Pu separation with U / TEVA resin : Influence of some parameters on chromatographic cycle performances. J Radioanal Nucl Chem. https://doi.org/10.1007/s10967-021-07986-4 Hernandez M, Quemet A, Montreuil L, Maillard C, Baghdadi S (2025) Investigation of chromatographic procedures for the analysis of cationic impurities in uranium and plutonium matrices by ICP-OES and ICP-MS. Spectrochim Acta Part B Spectrosc 107136. https://doi.org/10.1016/j.sab.2025.107136 Prohaska T, Irrgeher J, Zitek A, Jakubowski N (2014) Sector Field Mass Spectrometry for Elemental and Isotopic Analysis. New Developments in Mass Spectrometry. The Royal Society of Chemistry Joint Committee for Guides in Metrology (2008) JCGM 101:2008 Evaluation of measurement data — Supplement 1 to the Guide to the expression of uncertainty in measurement — Propagation of distributions using a Monte Carlo method. Jcgm 101:2008 Saltelli A (2002) Making best use of model evaluations to compute sensitivity indices. Comput Phys Commun 145:280–297. https://doi.org/10.1016/S0010-4655(02)00280-1 R Core Team (2023) R: A Language and Environment for Statistical Computing, Vienna, Austria. https://www.R-project.org Baghdadi S, Quémet A, Esbelin E, Manidren Y, Gracia S, Dalier V, Poinsignon-Jacquemin R, Huyghe L, Buravand E, Dautheribes JL, Rivier C (2017) Zr precipitation kinetics in irradiated fuel dissolution solution by TIMS and ICP-MS: a combined study. J Radioanal Nucl Chem 1–6. https://doi.org/10.1007/s10967-017-5602-6 Additional Declarations No competing interests reported. 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12:10:01","extension":"html","order_by":11,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":117692,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7748563/v1/3cba1603d6240a35949de614.html"},{"id":93771352,"identity":"53a45c21-45d9-4920-b5d6-f0b69d899588","added_by":"auto","created_at":"2025-10-17 12:02:01","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":210721,"visible":true,"origin":"","legend":"\u003cp\u003e\u003csup\u003e95\u003c/sup\u003eMo/\u003csup\u003e96\u003c/sup\u003eMo isotope ratio of the SRM 3134 for different measurements and conditions. The black circles are the individual measurements. The green triangles are the series average. Expanded uncertainties are given with a coverage factor of 2. The red solid line corresponds to the reference value and the red dotted lines represent its uncertainty at k=2.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7748563/v1/585365f0ab3c797eed44f352.png"},{"id":93771359,"identity":"15da0556-8c58-4609-bd8e-12a916bfabbd","added_by":"auto","created_at":"2025-10-17 12:02:01","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":63156,"visible":true,"origin":"","legend":"\u003cp\u003eElution curves of Mo for the TEVA resin. The experiment was performed twice. The uncertainty bars correspond to one standard deviation.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7748563/v1/70665c2441d0dd31bf8fe7b9.png"},{"id":93772526,"identity":"bffd8c9e-ec10-47b7-870f-8c81258bbe87","added_by":"auto","created_at":"2025-10-17 12:10:01","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":121330,"visible":true,"origin":"","legend":"\u003cp\u003eMo isotope abundances for the SRM 3134 and the three samples. Expanded uncertainties are given with a coverage factor of 2.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7748563/v1/a2bbdc9f3ff23fc17c83075e.png"},{"id":98814241,"identity":"c353a063-3a38-4f6d-87d5-79868254c75d","added_by":"auto","created_at":"2025-12-22 16:12:00","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1124190,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7748563/v1/e036a588-cab5-4961-b6ad-4ec07aa09203.pdf"},{"id":93771355,"identity":"db5702a4-a6f9-4585-b542-cd45cce0e6c9","added_by":"auto","created_at":"2025-10-17 12:02:01","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":869600,"visible":true,"origin":"","legend":"","description":"","filename":"ESIMo.docx","url":"https://assets-eu.researchsquare.com/files/rs-7748563/v1/92a10c7587f32a9e03eedce6.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Determination of molybdenum isotope abundances and ratios for nuclear samples analysis using Thermal Ionization Mass Spectrometry","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eMolybdenum (Mo) is classified as a transition metal and has seven naturally occurring stable isotopes (\u003csup\u003e92\u003c/sup\u003eMo, \u003csup\u003e94\u003c/sup\u003eMo, \u003csup\u003e95\u003c/sup\u003eMo, \u003csup\u003e96\u003c/sup\u003eMo, \u003csup\u003e97\u003c/sup\u003eMo, \u003csup\u003e98\u003c/sup\u003eMo and \u003csup\u003e100\u003c/sup\u003eMo). The analysis of its isotope ratios is interesting for the geochemistry, cosmochemistry, biochemistry and environmental studies [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Mo is also one of the major fission product [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. The Mo fission product is characterized by the presence of four major isotopes (\u003csup\u003e95\u003c/sup\u003eMo, \u003csup\u003e97\u003c/sup\u003eMo, \u003csup\u003e98\u003c/sup\u003eMo and \u003csup\u003e100\u003c/sup\u003eMo) [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. It is found in all stages during the treatment and recycling of the nuclear spent fuel. It is one constituent of dissolution fines that can clog the dissolver during the dissolution process [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. The accurate determination of its isotope composition helps to understand the nuclear processes. Its quantification can also be used to measure the spent fuel burn-up [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe Atalante facility of the French Alternative Energies and Atomic Energy Commission (CEA) is dedicated to the research and development on the backend of the fuel cycle and the reprocessing process of the spent nuclear fuel. The isotope analysis of Mo is an essential component of the research undertaken to enhance the characterization of nuclear spent fuel and dissolution fines. The isotope composition analysis of nuclear samples required specific installation (glove boxes, shieled lines) to be performed in safe condition. In the Atalante facility, only two instruments, able to perform isotopic measurement, are nuclearized (\u003cem\u003ei.e\u003c/em\u003e. modify to be used with radioactive sample): a simple quadrupole Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and a Thermal Ionization Mass Spectrometry (TIMS). TIMS can perform isotopic measurement with a greater accuracy than the quadrupole ICP-MS. Uncertainties below 1% can be obtained for a wide range of element [\u003cspan additionalcitationids=\"CR8 CR9\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eDue to its high first ionization potential (7.1eV), the measurement of Mo\u003csup\u003e+\u003c/sup\u003e ion is difficult [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Only low signal can be obtained using the positive mode of the TIMS [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. In other hand, it is now well established that its ionization efficacy is improved using the negative mode of the TIMS (N-TIMS) [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Its ionization is enhanced using an activator to form and detect the MoO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e species. Different activators with different proportion of lanthanum, calcium or gadolinium nitrate were previously tested by Nagai et Yokayama [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]: it was demonstrated that the optimal condition for Mo ionization is achieved when the Mo sample on the filament is covered by lanthanum nitrate, with a La/Mo ratio of 5. After correcting the oxygen isotopic interferences and the instrument isotope fractionation using an internal normalization, repeatabilities below 0.01% can be obtained on the Mo isotope ratios.\u003c/p\u003e\u003cp\u003eTo avoid isobaric interferences (\u003cem\u003ee.g\u003c/em\u003e. \u003csup\u003e96\u003c/sup\u003eMo/\u003csup\u003e96\u003c/sup\u003eRu/\u003csup\u003e96\u003c/sup\u003eZr) and possible competition between element ionization during the evaporation process, a purification step of the Mo is required. Liquid/liquid extraction [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], High Performance Liquid Chromatography (HPLC) [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], chemical process [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] or solid phase extraction (SPE) [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] can be used to obtain a pure fraction of Mo. SPE is easy to use in glove boxes or in shielded lines. However, the SPE protocols developed in the literature requires several resin separations [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e], a process that is time-consuming and results in an increase in the volume of radioactive effluents. Furthermore, the separation conditions require using HCl, that can be problematic when working in glove box condition. Indeed, to prevent the corrosion of the glove boxes, it is recommended to avoid it, whenever feasible. Radioactive effluent containing chlorine must also undergo treatment to comply with the relevant specifications prior to its evacuation.\u003c/p\u003e\u003cp\u003eThis paper presents an analytical procedure developed for the analysis of the Mo isotope ratios and isotope abundances using TIMS for nuclear samples. The development of two separation protocols without using HCl is reported herein. The initial protocol involves the combination of two distinct resins in the case of the analysis of both Mo and Zr isotope ratios. The second protocol uses a single resin for the purification of Mo. The TIMS results obtained on a standard solution will be discussed in terms of accuracy (\u003cem\u003ei.e.\u003c/em\u003e measurement trueness and precision) [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. The evaluation of the uncertainties will be conducted to ascertain the primary contributor to global uncertainty.\u003c/p\u003e"},{"header":"2. Experimental","content":"\u003cp\u003eMaterials, reagents and samples\u003c/p\u003e\u003cp\u003eAll dilutions were performed using deionized water obtained from a Milli-Q system (resistivity: 18.2 MΩ cm, Millipore, Milford). Nitric acid (w\u0026thinsp;=\u0026thinsp;67\u0026thinsp;\u0026minus;\u0026thinsp;70%, J.T. Baker) of Ultrex II reagent grade was used. Oxalic acid and lanthanum nitrate powder (purity\u0026thinsp;\u0026gt;\u0026thinsp;99.999%) was purchased from Sigma Aldrich. All dilutions were performed volumetrically using pre-calibrated micropipettes.\u003c/p\u003e\u003cp\u003eThe Mo reference solution was the SRM 3134 provided by the National Institute of Standards and Technology (NIST). The reference value for the isotope abundance that was retained was the one designated by the International Union of Pure and Applied Chemistry (IUPAC) [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Zr and Ru were provided by Analytica as natural monoelement standard solutions at 1000 mg L\u003csup\u003e-1\u003c/sup\u003e. A solution containing only Mo, hereafter referred to as \u0026lsquo;Mo solution\u0026rdquo; with a concentration of 50 mg L\u003csup\u003e-1\u003c/sup\u003e was prepared from the SRM 3134. A second solution, hereafter referred to as \u0026lsquo;Mo/Zr/Ru solution\u0026rdquo;, with a concentration of 50 mg L\u003csup\u003e-1\u003c/sup\u003e each was prepared from the monoelement solutions.\u003c/p\u003e\u003cp\u003e2 mL TEVA and UTEVA prepacked resins (Triskem, France) with 100\u0026ndash;150 \u0026micro;m particle size were used in gravity mode according to different separation procedure. The flow- rate was estimated to approximatively 25 mL h\u003csup\u003e-1\u003c/sup\u003e (v\u0026thinsp;=\u0026thinsp;50 cm h\u003csup\u003e-1\u003c/sup\u003e).\u003c/p\u003e\u003cp\u003eThe developed methodology was applied to three samples, hereafter referred to as \u0026ldquo;sample 1, 2 and 3\u0026rdquo;, to determine the Mo isotope abundance. All experiments were performed in glove boxes to work with radioactive solutions in safe experimental conditions. These samples came from experiments performed in the Atalante facility. The samples 1 and 2 came from the dissolution of solid samples obtained during the reprocessing of spent nuclear fuel. The sample 3 came from the dissolution of the spent nuclear fuel, performed in a shielded line. Sample 1 and 2 are similar and are the most challenging in terms of separation: [Mo]\u0026thinsp;\u0026asymp;\u0026thinsp;100 mg L\u003csup\u003e-1\u003c/sup\u003e, [Zr]\u0026thinsp;\u0026asymp;\u0026thinsp;1000 mg L\u003csup\u003e-1\u003c/sup\u003e, [U\u0026thinsp;+\u0026thinsp;Pu]\u0026thinsp;\u0026asymp;\u0026thinsp;10 mg L\u003csup\u003e-1\u003c/sup\u003e, gamma activity\u0026thinsp;=\u0026thinsp;5.10\u003csup\u003e8\u003c/sup\u003e Bq L\u003csup\u003e-1\u003c/sup\u003e, the concentration of Ru was unknown. The characteristics of the sample 3 are: [Mo]\u0026thinsp;\u0026asymp;\u0026thinsp;150 mg L\u003csup\u003e-1\u003c/sup\u003e, [Ru]\u0026thinsp;\u0026asymp;\u0026thinsp;1 mg L\u003csup\u003e-1\u003c/sup\u003e, [Zr]\u0026thinsp;\u0026asymp;\u0026thinsp;50 mg L\u003csup\u003e-1\u003c/sup\u003e, [U\u0026thinsp;+\u0026thinsp;Pu]\u0026thinsp;\u0026asymp;\u0026thinsp;400 mg L\u003csup\u003e-1\u003c/sup\u003e, gamma activity\u0026thinsp;=\u0026thinsp;3.10\u003csup\u003e9\u003c/sup\u003e Bq L\u003csup\u003e-1\u003c/sup\u003e. In the laboratory, the gamma activity of the sample is limited to 5.10\u003csup\u003e8\u003c/sup\u003e Bq L\u003csup\u003e-1\u003c/sup\u003e. Sample 3 was diluted 10-fold with 3 mol L\u003csup\u003e-1\u003c/sup\u003e nitric acid in a shielded line before the transfer to the glove box laboratory. The sample received in the laboratory contained 15 mg L\u003csup\u003e-1\u003c/sup\u003e of Mo. 5 mL of sample 1 and 2, and 1 mL of sample 3 were received in the laboratory.\u003c/p\u003e\u003cp\u003eSeparation procedure\u003c/p\u003e\u003cp\u003eTwo different separations protocols are proposed: (1) if only the Mo isotope abundance is required, the separation protocol is performed with a TEVA resin, and (2) if the Zr and the Mo isotope abundance is required, the separation protocol combines UTEVA and TEVA resin. The Zr purification is obtained after the UTEVA separation and the Mo purification is obtained after the TEVA separation. The experimental conditions for the Mo purification process are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eUTEVA and TEVA resins separation protocol.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eReagent\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eVolume (mL)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e\u003cp\u003e\u003cem\u003e1) UTEVA resin separation\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eConditioning\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4 mol\u0026nbsp;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e HNO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample feeding\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4 mol\u0026nbsp;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e HNO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMo/Ru elution\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4 mol\u0026nbsp;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e HNO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e\u003cp\u003e\u003cem\u003e2) TEVA resin separation\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eConditioning\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4 mol\u0026nbsp;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e HNO\u003csub\u003e3\u003c/sub\u003e / 0.2 mol\u0026nbsp;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e H\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample feeding\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4 mol\u0026nbsp;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e HNO\u003csub\u003e3\u003c/sub\u003e / 0.2 mol\u0026nbsp;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e H\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRu/Zr wash\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4 mol\u0026nbsp;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e HNO\u003csub\u003e3\u003c/sub\u003e / 0.2 mol\u0026nbsp;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e H\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e18\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOxalic acid wash\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1 mol\u0026nbsp;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e HNO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMo elution\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1 mol\u0026nbsp;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e HNO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eIf required the first step is the UTEVA separation. First, the HNO\u003csub\u003e3\u003c/sub\u003e concentration of the sample solution was adjusted to 4 mol L\u003csup\u003e-1\u003c/sup\u003e. After conditioning the UTEVA resin with 4.5 mL of 4 mol L\u003csup\u003e-1\u003c/sup\u003e HNO\u003csub\u003e3\u003c/sub\u003e, 1 mL of the sample solution was loaded onto the column. During this feeding step, Zr was fixed to the UTEVA resin. This step also helps to purify the Mo from U and Pu, which are the predominant elements in the nuclear samples, as they are fixed onto the resin [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Mo and Ru was eluted with 4.5 mL of 4 mol L\u003csup\u003e-1\u003c/sup\u003e HNO\u003csub\u003e3\u003c/sub\u003e. Feeding and elution fractions containing Mo and Ru were collected and reunited to be evaporated and redissolved with a (1 mol L\u003csup\u003e-1\u003c/sup\u003e/0.2 mol L\u003csup\u003e-1\u003c/sup\u003e) HNO\u003csub\u003e3\u003c/sub\u003e / H\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e mixture, to be in the optimal condition for the TEVA separation. If needed, the UTEVA resin is washed with 13.5 mL of 4 mol L\u003csup\u003e-1\u003c/sup\u003e HNO\u003csub\u003e3\u003c/sub\u003e and the Zr is eluted with 4.5 mL of (4 mol L\u003csup\u003e-1\u003c/sup\u003e/0.1 mol L\u003csup\u003e-1\u003c/sup\u003e) HNO\u003csub\u003e3\u003c/sub\u003e / H\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e mixture [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eIf the UTEVA separation protocol was not used prior, the first step of the TEVA separation is to adjust the acidity of the sample. For that, the sample is evaporated and redissolved with a (1 mol L\u003csup\u003e-1\u003c/sup\u003e/0.2 mol L\u003csup\u003e-1\u003c/sup\u003e) HNO\u003csub\u003e3\u003c/sub\u003e / H\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e mixture. After conditioning the TEVA resin with 4.5 mL of (1 mol L\u003csup\u003e-1\u003c/sup\u003e/0.2 mol L\u003csup\u003e-1\u003c/sup\u003e) HNO\u003csub\u003e3\u003c/sub\u003e / H\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e mixture, 1 mL of the solution was loaded onto the column. During this feeding step, the Mo was fixed to the TEVA resin. The Ru and the Zr, not retained by the resin, were wash with 18 mL of (1 mol L\u003csup\u003e-1\u003c/sup\u003e/0.2 mol L\u003csup\u003e-1\u003c/sup\u003e) HNO\u003csub\u003e3\u003c/sub\u003e / H\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e mixture. This step helps also purifying the Mo from U and Pu, which are the predominant elements in the nuclear samples, as they are not retained by the resin. The column was washed with 2.5 mL of 1 mol L\u003csup\u003e-1\u003c/sup\u003e HNO\u003csub\u003e3\u003c/sub\u003e, to avoid oxalic acid in the Mo elution solution. This volume was optimized to ensure that there was no loss of Mo during this step. Then, the Mo was eluted with 4.5 mL of 1 mol L\u003csup\u003e-1\u003c/sup\u003e HNO\u003csub\u003e3\u003c/sub\u003e. This solution was evaporated and redissolved with 0.5 mol L\u003csup\u003e-1\u003c/sup\u003e HNO\u003csub\u003e3\u003c/sub\u003e to obtain a Mo concentration of 1 \u0026micro;g \u0026micro;L\u003csup\u003e-1\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eICP-OES and ICP-MS\u003c/p\u003e\u003cp\u003eElution fractions were analyzed by Inductively Coupled Plasma \u0026ndash; Optical Emission Spectrometry (ICP-OES) to measure separation yield and decontamination factors. Analyses were performed using an Optima 8300 DV (Perkin Elmer) equipped with a micro-nebulizer and a small volume gutter cyclonic nebulization chamber. Each sample was diluted 10-fold with 0.5 mol L\u003csup\u003e-1\u003c/sup\u003e HNO\u003csub\u003e3\u003c/sub\u003e before analyzing by ICP-OES. Scandium (1 mg L\u003csup\u003e-1\u003c/sup\u003e) was used as internal standard. It helps monitoring matrices effects but no correction was applied. The main operation conditions were: plasma power\u0026thinsp;=\u0026thinsp;1300W, cooling gas flow rate\u0026thinsp;=\u0026thinsp;15 L min\u003csup\u003e-1\u003c/sup\u003e, outler gas flow rate\u0026thinsp;=\u0026thinsp;0.2 L min\u003csup\u003e-1\u003c/sup\u003e, nebulizer gas flow rate\u0026thinsp;=\u0026thinsp;0.6 L min\u003csup\u003e-1\u003c/sup\u003e, solution uptake rate\u0026thinsp;=\u0026thinsp;1 mL min\u003csup\u003e-1\u003c/sup\u003e and view mode\u0026thinsp;=\u0026thinsp;axial/radial. The wavelengths monitoring were 220.031, 203.845 and 204.597 nm for Mo, 361.383 nm for Sc, 257.139, 339.197, 343.823 and 354.262 nm for Zr and 240.272 and 349.894 nm for Ru. Results are expressed as the average of the concentration obtained on each individual wavelength. A single calibration standard was used. Limit of detections were determined by analyzing three blanks.\u003c/p\u003e\u003cp\u003eSeparation blanks were analyzed thanks to an Elan DRCe ICP-MS (Perkin Elmer) to ensure the separation procedure does not generate a Mo pollution. The main operation conditions were summarized in a previous study [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. \u003csup\u003e115\u003c/sup\u003eIn (1 \u0026micro;g L\u003csup\u003e-1\u003c/sup\u003e) was used as internal standard. The measured masses were 95 and 97 for the Mo determination and 115 for the internal standard.\u003c/p\u003e\u003cp\u003eTIMS\u003c/p\u003e\u003cp\u003eThe measurements were performed on a Thermo Scientific Triton TIMS equipped with a glove box. The instrument is equipped with 9 Faraday cups (all are movables except the central denoted C) which are coupled to 10\u003csup\u003e11\u003c/sup\u003e Ω current amplifiers. 4 Faraday cups are positioned in low masses (noted L1\u0026ndash;L4) and 4 Faraday cups are positioned in high masses (noted H1\u0026ndash;H4).\u003c/p\u003e\u003cp\u003e\u003cem\u003eSample loading\u003c/em\u003e\u003c/p\u003e\u003cp\u003eThe Mo isotopes were measured as MoO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e by N-TIMS. A single Re-filament configuration was used. These filaments (Re metal, purity 99.999%) are provided by ATES and were outgassed for 2h at 4.5 A in a high vacuum chamber (\u0026lt;\u0026thinsp;5 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e mbar) before use. The optimal time will be discussed in the results section. 1 \u0026micro;L of Mo sample solution (1 \u0026micro;g or 250 ng of Mo) was loaded onto the filament and dried at 0.4 A, then covered by 1 \u0026micro;L of La(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e solution (5 \u0026micro;g of La) as an activator, yielded a La/Mo ratio of 5 [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. When the sample and the activator are completely dried, the filament is heated until a dull red color was observed.\u003c/p\u003e\u003cp\u003e\u003cem\u003eMeasurement of Mo isotope ratios\u003c/em\u003e\u003c/p\u003e\u003cp\u003eThe sample filament was placed in the ion source. When the vacuum in the ion source is optimal (\u0026lt;\u0026thinsp;1.10\u003csup\u003e-7\u003c/sup\u003e mbar), the filament is heated to 2 A in 20 min. The gate valve that permits ions to access the sector flied is then opened. The evaporation filament is heated to obtain the major isotope ions beam of 10 mV. A \u0026ldquo;peak center\u0026rdquo; (mass calibration and ions beam centering in the detector) and the lenses optimization of the ion source are performed on the major isotope ion beam. The analysis is started when the major isotope ions beam reaches a minimum of 200 mV by heating the filament. The filament temperature was controlled to keep the ion beam intensity constant during the measurement, by increasing the current when necessary. Each measurement corresponded to 10 blocks of 10 cycles with an integration time of 8 s.\u003c/p\u003e\u003cp\u003e\u003cem\u003eData processing\u003c/em\u003e\u003c/p\u003e\u003cp\u003eWhen molybdenum is ionized in TIMS, it takes the form of MoO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e. However, the presence of oxygen results in isobaric interference due to the varying oxygen isotopes (\u003csup\u003e16\u003c/sup\u003eO, \u003csup\u003e17\u003c/sup\u003eO and \u003csup\u003e18\u003c/sup\u003eO). The oxygen correction was previously detailed in the literature and are summarized in the Electronic Supplementary Information (ESI) [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe isotope fractionation was corrected thanks to the exponential law [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Two different normalizations were used: the internal and the external normalization [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. For the isotope ratios measurement without separation, the measured ratios were corrected internally using the \u003csup\u003e98\u003c/sup\u003eMo/\u003csup\u003e96\u003c/sup\u003eMo ratio (1.4568(19) [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]). Such normalization can\u0026rsquo;t be applied to samples with non-natural isotope abundance, as there is no known isotope ratio that can be considered as a reference ratio. All ratios measured after a separation step were corrected using an external normalization, even for the natural Mo, as the goal of this study is to measured three samples coming from the nuclear fuel cycle. The determination of the average normalization factor was achieved by measuring the \u003csup\u003e98\u003c/sup\u003eMo/\u003csup\u003e96\u003c/sup\u003eMo ratio of the SRM 3134 several times: the mean of these measurement was 1.4549 with a standard deviation of 0.0053. To ensure the correction was accurate, the SRM 3134 was analyzed using the external normalization before and after each measurement series.\u003c/p\u003e\u003cp\u003eSeparation tests and TIMS experiments\u003c/p\u003e\u003cp\u003eTo guarantee the efficacy of the TIMS measurement, the SRM 3134 was measured 11 times without separation in 4 distinct measurement series. The mean of the eleven \u003csup\u003e98\u003c/sup\u003eMo/\u003csup\u003e96\u003c/sup\u003eMo measured ratio lead to the determination of the isotope fractionation correction factor used for the external normalization. To verify the instrument and the reliability of the isotope fractionation correction factor, the SRM 3134 was measured before and after each measurement series involving samples that had undergone a separation. A total of 10 measurements were conducted on a deposit of 1 \u0026micro;g, while 5 measurements were performed on a deposit of 250 ng. Different deposits were analyzed to estimate the impact of a pollution of Zr and/or Ru on the Mo measurements: 3 deposits of Mo and Zr with m(Zr)/m(Mo)\u0026thinsp;=\u0026thinsp;1, 3 deposits of Mo and Ru with m(Ru)/m(Mo)\u0026thinsp;=\u0026thinsp;1, 2 deposits of Mo and Zr with m(Zr)/m(Mo)\u0026thinsp;=\u0026thinsp;10 and 2 deposits of Mo, Zr and Ru with a 1/1/1 ratio.\u003c/p\u003e\u003cp\u003eThe first step for the separation development helped determining the volume of 1 mol L\u003csup\u003e-1\u003c/sup\u003e HNO\u003csub\u003e3\u003c/sub\u003e for washing the oxalic acid for the TEVA column, which was used for the elution of the Ru and the Zr, without the elution the Mo. TEVA separation were performed on the Mo solution. The 1 mol L\u003csup\u003e-1\u003c/sup\u003e HNO\u003csub\u003e3\u003c/sub\u003e was added in several small volumes, after which the elution fractions were measured by ICP-OES to determine the Mo recovery yield in each fraction. The experiments were reproduced 2 times.\u003c/p\u003e\u003cp\u003eThen, the TEVA protocol (with the appropriate volume of 1 mol L\u003csup\u003e-1\u003c/sup\u003e HNO\u003csub\u003e3\u003c/sub\u003e previously determined to wash the oxalic acid) was used on the Mo solution. The different fractions were measured by ICP-OES to determine the Mo recovery yield in each of them. The TEVA protocol was used on the Mo/Zr/Ru solution to demonstrate the Mo purification. The UTEVA\u0026thinsp;+\u0026thinsp;TEVA protocol were used on the Mo/Zr/Ru solution to demonstrate the Mo purification and its effect on the measurement of isotope ratios. All separation experiments were reproduced 3 times. The different elution fractions were measured by ICP-OES to determine the cation recovery yield in each fraction and the associated decontamination factor. The Mo elution fractions were measured by TIMS. Two deposits for each separation were performed, totaling six results.\u003c/p\u003e\u003cp\u003eChemical blanks were also prepared for the UTEVA and TEVA separation protocol: they consist in performing a separation using 1 mol L\u003csup\u003e-1\u003c/sup\u003e HNO\u003csub\u003e3\u003c/sub\u003e and 4 mol L\u003csup\u003e-1\u003c/sup\u003e HNO\u003csub\u003e3\u003c/sub\u003e / 0.2 mol L \u003csup\u003e-1\u003c/sup\u003e H\u003csub\u003e2\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e, respectively, as a loading solution instead of the Mo/Zr/Ru solution to demonstrate the absence of these cations in the reactants and resins. The Mo fractions were measured by ICP-MS. The experiments were reproduced 3 times.\u003c/p\u003e\u003cp\u003eThe UTEVA\u0026thinsp;+\u0026thinsp;TEVA protocol was used on samples 1 and 2 as the Zr isotope composition was needed. The Mo elution fractions were measured by TIMS. The experiments were reproduced 3 times for each sample. Two deposits for each separation were performed, yielding a total of six results. For sample 3, the TEVA protocol was used as only the Mo isotope composition was required. The sample volume and the Mo quantity being limited for this sample, minor adjustments were made to the protocol: (1) the experiments were reproduced twice instead of three times. (2) The Mo concentration loaded on the column was about 7 mg L\u003csup\u003e-1\u003c/sup\u003e instead of 50 mg L\u003csup\u003e-1\u003c/sup\u003e. (3) The Mo quantity deposited in the filament was 250 ng instead of 1 \u0026micro;g (the activator quantity was adapted to ensure a La/Mo ratio of 5). (4) Each separation was measured three times by TIMS instead of two (totaling of six results).\u003c/p\u003e\u003cp\u003eResults evaluation and uncertainties estimation\u003c/p\u003e\u003cp\u003eThe cations (Mo, Zr or Ru) separation performances were estimated using the recovery yield (RY, Eq.\u0026nbsp;(\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e)).\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:RY\\left(cation\\right)\\:\\left(\\text{%}\\right)=\\frac{{\\left[cation\\right]}_{after\\:sep}}{{\\left[cation\\right]}_{before\\:sep}}\\bullet\\:\\frac{{V}_{elution}}{{V}_{loading}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eWhere \u003cem\u003e[cation]\u003c/em\u003e\u003csub\u003e\u003cem\u003eafter sep\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003e[cation]\u003c/em\u003e\u003csub\u003e\u003cem\u003ebefore sep\u003c/em\u003e\u003c/sub\u003e are the Mo, Zr or Ru concentration after and before separation, respectively, and V is the volume of solution.\u003c/p\u003e\u003cp\u003eThe decontamination factors of Mo in regard of Zr (DF(Mo/Zr)) and Ru (DF(Mo/Ru) were used to evaluate the purity of the recovered fractions (Eq.\u0026nbsp;(\u003cspan refid=\"Equ2\" class=\"InternalRef\"\u003e2\u003c/span\u003e)). An increase in the DF results in enhanced separation efficiency.\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\:DF(Mo/Zr\\:or\\:Ru)\\:\\left(\\text{%}\\right)=\\frac{RY\\left(Mo\\right)}{RY\\left(Zr\\:or\\:Ru\\right)}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe efficiency of the separation process was determined by the following criteria: a Mo recovery yield falling in the range of 80\u0026ndash;120% and a DF greater than 100.\u003c/p\u003e\u003cp\u003eBias, or trueness, was calculated using Eq.\u0026nbsp;(\u003cspan refid=\"Equ3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003cdiv id=\"Equ3\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ3\" name=\"EquationSource\"\u003e\n$$\\:Bias\\:\\left(\\text{%}\\right)=\\frac{\\stackrel{-}{x}\\:-ref}{ref}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e3\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eWhere \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\stackrel{-}{x}\\)\u003c/span\u003e\u003c/span\u003e is the mean of the measurement series and \u003cem\u003eref\u003c/em\u003e is the reference value [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eEq.\u0026nbsp;(\u003cspan refid=\"Equ4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) was used to determine whether the mean of the measurement series has a statistically significant bias compare to reference values. If the zeta-score is lower than 2, the final mean value is considered to have no statistically significant bias. If the zeta-score is between 2 and 3, the accuracy of the final mean value is questionable. If the zeta-score is higher than 3, the final mean value is considered having a statistically significant bias.\u003cdiv id=\"Equ4\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ4\" name=\"EquationSource\"\u003e\n$$\\:\\text{Z}\\text{e}\\text{t}\\text{a}-\\text{s}\\text{c}\\text{o}\\text{r}\\text{e}=\\frac{\\left|\\stackrel{-}{x}-ref\\right|}{\\sqrt{{u}^{2}\\left(\\stackrel{-}{x}\\right)+{u}^{2}\\left(ref\\right)}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e4\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003ewith \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:u\\left(\\stackrel{-}{x}\\right)\\)\u003c/span\u003e\u003c/span\u003e being the standard uncertainty of the mean of the measurement series and \u003cem\u003eu(ref)\u003c/em\u003e the reference value standard uncertainty.\u003c/p\u003e\u003cp\u003eThe uncertainties were estimated using a bottom-up approach by taking into account all conceivable sources of uncertainty to be assessed [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]: reference value uncertainty for the determination of the fractionation factor, oxygen isotope ratio, collected intensities, inter-calibration gain, baseline, etc. The uncertainties were estimated using the Monte Carlo Method (MCM), as recommended in the supplement 1 of the Guide to the Expression of Uncertainty in Measurement (GUM) [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. The uncertainty budget was established using the sensitivity indices (Sobol indices) [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. All the calculations were made using R software (free of use) [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e].\u003c/p\u003e"},{"header":"3. Results and discussion","content":"\u003cp\u003eTIMS measurement conditions\u003c/p\u003e\u003cp\u003eThe results of the TIMS measurement for the \u003csup\u003e95\u003c/sup\u003eMo/\u003csup\u003e95\u003c/sup\u003eMo isotope ratio are illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The full set of results can be found in Tables S3 to S10 in the ESI.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cem\u003eBlank of filament\u003c/em\u003e\u003c/p\u003e\u003cp\u003eFilaments blanks were analyzed with and without activator in two ways: first, without outgassing, and then after outgassing for 20 minutes and 2 hours. Without outgassing, the total signal from all the Mo isotopes was about 10 mV, and correspond to natural Mo. When the filaments were outgassed 20 min, the total signal from all the isotopes decreased compared to non-degassed filaments and was about 4 mV. For filaments outgassed 2h, no signal was observed except for one filament where a small signal was observed: the total signal from all the Mo isotopes was about 0.5 mV for the first 50 integrations. After that the signal was below the detection limit of the Faraday cup. This signal is small and negligible compared to the measured signal of the sample (\u0026gt;\u0026thinsp;200 mV). For the rest of this study, only filaments outgassed for 2h were used.\u003c/p\u003e\u003cp\u003e\u003cem\u003eMeasurement of the SRM 3134 using internal normalization\u003c/em\u003e\u003c/p\u003e\u003cp\u003eThe data acquired on the SRM 3134 without separation using the internal normalization were compared to the reference value (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and Table S2 in the ESI). The RSD values were found to be less than 0.02% and a bias below 0.04% were observed for all isotope ratios. The relative expanded uncertainties were estimated to be less than 0.1% for the \u003csup\u003e95\u003c/sup\u003eMo/\u003csup\u003e96\u003c/sup\u003eMo and \u003csup\u003e97\u003c/sup\u003eMo/\u003csup\u003e96\u003c/sup\u003eMo ratios, and between 0.1% and 0.3% for the remaining isotope ratios. As demonstrated by the zeta-scores falling below 2, no statistically significant biases were identified when compared to reference values.\u003c/p\u003e\u003cp\u003e\u003cem\u003eMeasurement of the SRM 3134 using external normalization\u003c/em\u003e\u003c/p\u003e\u003cp\u003eThe data acquired for a deposit of 1\u0026micro;g of the SRM 3134 without separation using the external normalization, analyzed before and after each separation series, were compared to the reference value (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and Table S3 in the ESI). The repeatabilities (between 0.08% and 0.4%) and the uncertainties (between 0.3% and 1.5%) were higher than the ones determined using the internal normalization. No statistically significant biases were identified in comparison to the reference value (zeta-scores below 2). These data obtained using the internal and external normalization help guarantying the reliability of the measurement results. For a deposit of 250ng, the zeta-scores below 2 confirms the accuracy of the results for this deposited amount (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and Table S4 in the ESI).\u003c/p\u003e\u003cp\u003e\u003cem\u003eMeasurement of Mo, Zr and Ru mixtures without separation\u003c/em\u003e\u003c/p\u003e\u003cp\u003eThe results obtained for the Zr/Mo and Ru/Mo mixtures with a mass ratio of 1 showed no difference compared to the reference values (zeta-score below 2): the RSD (below 0.015%), the biases (below 0.05%) and the estimated uncertainties were similar compared to the values obtained for a pure Mo solution (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and Table S5 in the ESI). It appears that Zr and Ru do not form the ZrO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e and RuO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e species whit the La(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e activator. No differences were observed during the analyses of the Zr/Mo mixture compared to the pure Mo solution: the Mo analyses were performed with a filament current between 2100 and 2400 mA. The analyses of the Ru/Mo mixtures exhibited slight variations. The analyses were performed at higher temperature: the filament currents were between 2500 and 2900 mA. Moreover, for two deposits, only 60 and 70 measurement cycles could be taken. It hypothesized that the presence of Ru functions as an inhibitor of Mo evaporation and ionization.\u003c/p\u003e\u003cp\u003eFor Zr/Mo solutions with a mass ratio of 10, corresponding to the ratio in samples 1 and 2, the analyses were difficult. Only one deposit was analyzed as no signal was observed for the second. Only 60 cycles were measured. The total signal from all the isotopes was about 180 mV, which is less than the 2 V obtained for a pure Mo solution. The results showed no statistical differences compared to the reference values (zeta-score below 2).\u003c/p\u003e\u003cp\u003eFor the Mo/Ru/Zr solution, only one deposit was analyzed. No signal was observed for the second deposit. Only 80 measurement cycles were obtained with a filament current ranging from 2500 to 2950 mA. However, the results showed no statistical differences compare to the reference values (zeta-score below 2). The biases (below 0.1%) and the estimated uncertainties are comparable to the ones obtained for a pure Mo solution.\u003c/p\u003e\u003cp\u003eAlthough the results for the Mo/Zr/Ru mixtures were in agreement with the reference values, a separation step is required to maximize the Mo signal and to avoid having to reanalyze a sample in the event of no signal. The analyses of mixtures demonstrated a high failure rate. Nevertheless, the results showed a minor contamination of the Mo fraction by Ru or Zr will exert an insignificant influence on the measurement of Mo isotope ratios.\u003c/p\u003e\u003cp\u003eOptimization of the oxalic acid washing of the TEVA separation\u003c/p\u003e\u003cp\u003eThe first separation tests were performed using no oxalic acid wash: \u003cem\u003ei.e\u003c/em\u003e. the Mo was eluted with 4.5 mL of nitric acid directly after the Zr/Ru elution. During the concentration step, prior to its deposition on the filament, the solution must be evaporated to dryness. This will result in the appearance of a white crystal, thereby rendering its redissolution with a small acid volume difficult (Figure \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e in the ESI). Moreover, the TIMS deposit was not clean. To ensure the complete removal of residual oxalic acid, it is necessary to add a volume of nitric acid. This preparatory step is a prerequisite for the subsequent execution of the Mo elution process.\u003c/p\u003e\u003cp\u003eThe results for the optimization of the oxalic acid wash are summarized in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Before 2.6 mL of nitric acid, the Mo was not detected. Mo was eluted from a volume of 2.6 mL and was recovered up to 4.7 mL. A volume of nitric acid of 2.5 mL was chosen for the oxalic acid wash. The Mo was then eluted with 4.5 mL of nitric acid.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe analyses of three Mo solution by adding this oxalic acid wash confirmed the good recovery of Mo: recovery\u0026thinsp;=\u0026thinsp;99.3% with an RSD of 1.3%. In the oxalic acid wash fraction, the Mo was not detected. The evaporation of the Mo fraction showed no white crystal, confirming the elimination of most of the oxalic acid (Figure \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e in the ESI). This helps to obtain a good concentration step and a clean deposit on the filament.\u003c/p\u003e\u003cp\u003eThe measured isotope ratios of the Mo solution after the TEVA separation, corrected using an external normalization, were in agreement with the reference values (zeta-score below 2 for all isotope ratios, Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and Table S6 in the ESI). The repeatabilities (RSD between 0.10 and 0.53%) and the estimated relative uncertainties (between 0.3 and 1.5%) were similar to the one observed for the SRM 3134 solution without separation using the external normalization.\u003c/p\u003e\u003cp\u003eTEVA separation on the Mo/Zr/Ru solutions\u003c/p\u003e\u003cp\u003eThe Mo, Zr and Ru recovery yields for the TEVA separation were showed in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. About 100% of the Zr was recovered in the sample loading and Ru/Zr elution fraction. The Ru was not entirety eluted in this fraction (about 65%). Ru has a complex chemistry. During the evaporation step before the sample loading, the Ru can be evaporated as RuO\u003csub\u003e4(g)\u003c/sub\u003e. Mo, Ru or Zr were not found in the oxalic acid wash fraction. 101% of the Mo was recovered in the Mo elution fraction. In this fraction, Zr was below the detection limit of the ICP-OES and 0.2% of the Ru was recovered. The DF(Mo/Zr) was greater than 1000 and DF(Mo/Ru) was about 500, confirming the effective purification of Mo against Ru and Zr.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eElemental recovery (mean) and one standard deviation (SD) of Zr, Mo and Ru for the TEVA separation.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"7\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eElution fraction\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003eZr\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003eMo\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003eRu\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMean\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eSD\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eMean\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eSD\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eMean\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eSD\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample loading and Ru/Zr elution\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.151\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.018\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.035\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.008\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.648\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.050\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOxalic acid wash\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMo elution\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.011\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.011\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.002\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe measured isotope ratios of the Mo fraction were in agreement with the reference values (zeta-score below 2 for all isotope ratios, Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and Table S7 in the ESI). The repeatabilities (RSD between 0.05 and 0.3%) and the estimated relative uncertainties (between 0.3 and 1.5%) were similar to the one observed for the SRM 3134 solution without separation using the external normalization. These measurements help confirming the efficacy of the Mo measurement after the separation of Mo/Zr/Ru solution.\u003c/p\u003e\u003cp\u003eUTEVA\u0026thinsp;+\u0026thinsp;TEVA separation on the Mo/Zr/Ru solution\u003c/p\u003e\u003cp\u003eThe Mo, Zr and Ru recovery yields for the UTEVA\u0026thinsp;+\u0026thinsp;TEVA separation were showed in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The first test was performed without any evaporation/redissolution prior to the UTEVA separation. During this separation step, Mo and Zr were coeluted: Zr and Mo recoveries are about 90% and 102%, respectively (test 1 in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The DF(Mo/Zr) was about 1.1. This effect has no impact on the Mo purification as the TEVA separation, which is performed after the UTEVA separation for Mo/Ru separation, helps to separate Mo and Zr.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eElemental recovery (mean) and one standard deviation (SD) of Zr, Mo and Ru for the UTEVA\u0026thinsp;+\u0026thinsp;TEVA separation.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"8\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eElution fraction\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eTest\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003eZr\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003eMo\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c8\" namest=\"c7\"\u003e\u003cp\u003eRu\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eMean\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eSD\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eMean\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eSD\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eMean\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003eSD\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eUTEVA separation\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSolution after evaporation and dissolution\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1\u003c/p\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003cp\u003e0.985\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003cp\u003e0.004\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003cp\u003e1.054\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-\u003c/p\u003e\u003cp\u003e0.092\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e-\u003c/p\u003e\u003cp\u003e1.020\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e-\u003c/p\u003e\u003cp\u003e00087\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample loading and Mo/Ru elution\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1\u003c/p\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.903\u003c/p\u003e\u003cp\u003e0.786\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.004\u003c/p\u003e\u003cp\u003e0.009\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1.020\u003c/p\u003e\u003cp\u003e0.868\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.006\u003c/p\u003e\u003cp\u003e0.034\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e1.015\u003c/p\u003e\u003cp\u003e0.816\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.005\u003c/p\u003e\u003cp\u003e0.038\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eTEVA separation\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSolution after evaporation and dissolution\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1\u003c/p\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.899\u003c/p\u003e\u003cp\u003e0.778\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.002\u003c/p\u003e\u003cp\u003e0.015\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.964\u003c/p\u003e\u003cp\u003e0.872\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.012\u003c/p\u003e\u003cp\u003e0.021\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.977\u003c/p\u003e\u003cp\u003e0.426\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.005\u003c/p\u003e\u003cp\u003e0.038\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample loading and Ru/Zr elution\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1\u003c/p\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.924\u003c/p\u003e\u003cp\u003e0.793\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.016\u003c/p\u003e\u003cp\u003e0.014\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.002\u003c/p\u003e\u003cp\u003e0.007\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.002\u003c/p\u003e\u003cp\u003e0.003\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.761\u003c/p\u003e\u003cp\u003e0.319\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.020\u003c/p\u003e\u003cp\u003e0.017\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOxalic acid wash\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1\u003c/p\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.001\u003c/p\u003e\u003cp\u003e0.005\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.001\u003c/p\u003e\u003cp\u003e0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.004\u003c/p\u003e\u003cp\u003e0.002\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.001\u003c/p\u003e\u003cp\u003e0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMo elution\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1\u003c/p\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.810\u003c/p\u003e\u003cp\u003e0.862\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.018\u003c/p\u003e\u003cp\u003e0.015\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.006\u003c/p\u003e\u003cp\u003e0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.002\u003c/p\u003e\u003cp\u003e0.002\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe behavior of Zr during the UTEVA separation process was found to be unexpected. This separation step is frequently performed in the laboratory for Zr isotope ratio analysis in complex samples [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. During these analyses, the Zr was fixed in the UTEVA resin. The only discrepancy observed was in the step involving the addition of a small quantity of Al\u003csup\u003e3+\u003c/sup\u003e to neutralize the fluoride. Fluoride, a constituent of the standard, has been proven to complex with Zr, thereby impeding its retention to the UTEVA resin. Here, this step was not employed to avoid a coelution of Al and Mo. The presence of Al and Mo in the same fraction is problematic during the filament deposit. In a previous study, this Al addition step was also not performed during the separation of cationic impurities in uranium and plutonium matrices [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. The solution, which must be separated, contained fluoride due to the dissolution protocol. During the separation step, about 84% of the Zr was retained into the UTEVA column, using a protocol analogous to the one that has been employed here.\u003c/p\u003e\u003cp\u003eDifferent tests were performed to try to understand and fix this strange behavior. First, the protocol was applied without any modification (same UTEVA protocol, same solution, same eluent). As expected, Zr was still not retained in the UTEVA resin: the Zr recovery was about 107%. Then, the protocol was modified: same UTEVA protocol, new solution, new eluent. Zr was still not retained onto the resin (recovery\u0026thinsp;=\u0026thinsp;109%), confirming there were no problem during the preparation of the solutions and the eluents. The hypothesis was formulated that the presence of fluoride would result in disrupting the Zr behavior in the resin. Consequently, an evaporation/dissolution step was incorporated prior to the UTEVA resin. During the evaporation, the fluoride was evaporated. The implementation of this additional step resulted in the recovery of only 2% of the Zr in the Mo fraction: the Zr was now fixed onto the resin.\u003c/p\u003e\u003cp\u003eTo consolidate the modification of the protocol, three UTEVA\u0026thinsp;+\u0026thinsp;TEVA separation protocols were applied on the Mo/Zr/Ru solution (test 2 in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The evaporation/redissolution step did not cause any loss of Mo, Ru or Zr. The recoveries after the evaporation/redissolution step were about 100% for the three elements. However, the Zr was still present in the Mo fraction during the UTEVA separation step (recovery about 80% with a standard deviation of about 1%). After the TEVA separation step, the Mo was well purified: the recovery of the Mo was about 86%, the DF(Mo/Zr) was greater than 800 and DF(Mo/Ru) was about 800, confirming the effective purification of Mo against Ru and Zr. Experiments were still in progress to understand the behavior of the Zr.\u003c/p\u003e\u003cp\u003eThe measured isotope ratios of the Mo fractions were in agreement with the reference values (zeta-score below 2 for all isotope ratios, Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and Table S8 in the ESI). The repeatabilities (RSD between 0.05 and 0.3%) and the estimated relative uncertainties (between 0.3 and 1.5%) were similar to the one observed for the SRM 3134 solution with or without separation using the external normalization. These measurements helped to confirm the efficacy of the Mo measurement after the separation of Mo/Zr/Ru solution using a combination of the UTEVA and TEVA resins.\u003c/p\u003e\u003cp\u003eBlanks of the separation\u003c/p\u003e\u003cp\u003eThe blanks of the TEVA and UTEVA separations showed a concentration in the Mo fraction of 160 ng L\u003csup\u003e-1\u003c/sup\u003e with an RSD of 14% and 70 ng L\u003csup\u003e-1\u003c/sup\u003e with an RSD of 38%, respectively. This corresponds to a Mo mass of about 720 fg and 310 fg present in the Mo fraction, respectively. Depending on the volume of liquid used during the evaporation/redissolution step prior to the sample deposit, the amount of Mo mass deposited onto the filament was estimated between 6 and 150 fg. This quantity is negligible in comparison to the quantity of sample deposited (1 \u0026micro;g, with the exception of sample 3, where 250 ng were deposited) on the filament. The Mo sample over the Mo pollution ratio is higher than 1700.\u003c/p\u003e\u003cp\u003eMo isotope abundance in three nuclear samples\u003c/p\u003e\u003cp\u003eThe results for the three samples are illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e and are presented in Table S9 in the ESI. The isotope ratios are presented relative to the \u003csup\u003e95\u003c/sup\u003eMo isotope, which is one of the four major isotopes, as the \u003csup\u003e96\u003c/sup\u003eMo isotope, used by convention for natural Mo, is a minor isotope. The isotope abundances of the three samples are quite different from natural Mo one. The isotope abundances of the seven isotopes are very similar for natural Mo (between 9 and 25% [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]). For the three samples, \u003csup\u003e95\u003c/sup\u003eMo, \u003csup\u003e97\u003c/sup\u003eMo, \u003csup\u003e98\u003c/sup\u003eMo and \u003csup\u003e100\u003c/sup\u003eMo isotopes are the major isotopes with similar isotope abundance (about 25%). The \u003csup\u003e96\u003c/sup\u003eMo isotopes has an isotope abundance about 1%. \u003csup\u003e92\u003c/sup\u003eMo and \u003csup\u003e94\u003c/sup\u003eMo isotopes were detected in minor proportion (below 0.3%).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe isotope composition of samples 1 and 2 are similar, with a difference in the isotope composition of the four major isotopes of less than 0.2%. Given the observed similarity in the provenance of the samples, analogous isotope abundance are to be expected. The isotope abundance of sample 3 differs from samples 1 and 2, thereby confirming the different provenance of the samples. The measurement repeatabilities (RSD\u0026thinsp;\u0026lt;\u0026thinsp;0.6%) observed for the \u003csup\u003e97\u003c/sup\u003eMo/\u003csup\u003e95\u003c/sup\u003eMo, \u003csup\u003e98\u003c/sup\u003eMo/\u003csup\u003e95\u003c/sup\u003eMo and \u003csup\u003e100\u003c/sup\u003eMo/\u003csup\u003e95\u003c/sup\u003eMo major isotope ratio are similar to the ones observed for natural Mo. Finally, the relative uncertainties were estimated to be less than 1% for the isotope abundance of the four major isotope ratios.\u003c/p\u003e\u003cp\u003eUncertainty budget\u003c/p\u003e\u003cp\u003eThe uncertainty budget, estimated using the sensitivity indices, were illustrated in Table S9 in the ESI for the natural Mo and in the Table S10 in the ESI for the samples.\u003c/p\u003e\u003cp\u003eOnly two parameters contribute to the uncertainty of the SRM 3134 isotope ratios using the internal normalization. The main contributor (between 77 and 96%) is the certified value of the \u003csup\u003e98\u003c/sup\u003eMo isotope abundance. The impact of the uncertainty of the \u003csup\u003e18\u003c/sup\u003eO/\u003csup\u003e16\u003c/sup\u003eO isotope ratio is limited (less than 10% of the budget), with the exception of the \u003csup\u003e97\u003c/sup\u003eMo/\u003csup\u003e96\u003c/sup\u003eMo isotope ratio, for which it accounts for 19%. The remaining parameters (gain, baseline, measured signal, \u003csup\u003e17\u003c/sup\u003eO/\u003csup\u003e16\u003c/sup\u003eO, certified value of the \u003csup\u003e96\u003c/sup\u003eMo isotope abundance) exert minimal influence on the global uncertainty (below 5% maximum). It is imperative that the uncertainties of the SRM 3134 isotope ratios are improved to enhance the reliability of the isotope ratios measured using internal normalization.\u003c/p\u003e\u003cp\u003eOnly one parameter contributes to the uncertainty of the isotope ratios of the SRM 3134 solution using the external normalization. It has been determined that a minimum of 95% of the global uncertainty is attributable to the uncertainty surrounding the measured \u003csup\u003e98\u003c/sup\u003eMo/\u003csup\u003e96\u003c/sup\u003eMo (\u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003emes\u003c/em\u003e\u003c/sub\u003e), which is used for external normalization. The standard uncertainty of \u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003emes\u003c/em\u003e\u003c/sub\u003e was estimated to be 0.36%, which in turn limited the isotope ratios uncertainty. An improvement of the measurement repeatability for the determination of \u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003emes\u003c/em\u003e\u003c/sub\u003e is needed to improve the uncertainty of the isotope ratios corrected using an external normalization.\u003c/p\u003e\u003cp\u003eThe aforementioned conclusion can also be drawn in relation to the uncertainty surrounding the \u003csup\u003ei\u003c/sup\u003eMo/\u003csup\u003e95\u003c/sup\u003eMo isotope ratios and the \u003csup\u003e96\u003c/sup\u003eMo and \u003csup\u003ei\u003c/sup\u003eMo abundances for the three samples (with i\u0026thinsp;=\u0026thinsp;96, 97, 98 or 100). A minimum of 80% of the global uncertainty is linked to the uncertainty surrounding the measured \u003csup\u003e98\u003c/sup\u003eMo/\u003csup\u003e96\u003c/sup\u003eMo (\u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003emes\u003c/em\u003e\u003c/sub\u003e), which is used for external normalization. For the two lower isotopes ratios (\u003csup\u003e92\u003c/sup\u003eMo/\u003csup\u003e95\u003c/sup\u003eMo and \u003csup\u003e94\u003c/sup\u003eMo/\u003csup\u003e95\u003c/sup\u003eMo), the measured signals are low especially for the sample 3 where the measured signal for masses 140 and 142 are about 0.6 and 0.4 mV, respectively. The baselines become a significant contributing factor.\u003c/p\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eThis study aimed to develop a separation protocol combines with TIMS measurement to perform the molybdenum isotopic analysis of nuclear samples. Despite being possible accurate measurement of Mo polluted by Zr and Ru, purification of Mo is required to enhance the collected signal. It appears that the formation of ZrO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e and RuO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e is not possible under these conditions (Re mono filament and La(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e activator). The protocol was first developed and tested on simulated solutions. The optimization of the TEVA protocol helped to limit the presence of oxalic acid in the Mo fraction and improved the implementation of the TIMS deposit. Separation protocols were found to be effective with recovery yields between 80 and 120%. The decontamination factor of Mo in regard of Zr and Ru was excellent and largely greater than 100. However, the understanding surprising behavior of Zr in the UTEVA is still in progress.\u003c/p\u003e\u003cp\u003eThe developed protocols were applied to analyze three nuclear samples. Significant differences were observed between the samples derived from distinct fuels, linked to their different burn-up profiles. The relative uncertainties in the isotope abundances of the main isotopes were estimated to be less than 1%, which is in agreement with the specifications of the project. To improve these uncertainties, an improvement of the isotope fractionation factor uncertainty is required. This can only be done by improving the repeatability of the uncorrected isotope ratio used to calculate the isotope fractionation factor by developing new TIMS methods. It would also be interesting to decrease the analyzable quantity to measure small quantity of Mo. For example, the samples received in the laboratory after the dissolution of transmutation discs contains only a few dozen of ng of Mo.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eAlexandre Quemet: Conceptualization, Investigation, Methodology, Writing - Original Draft, Supervision\u003c/p\u003e\n\u003cp\u003eLuna Borchi: Investigation, Methodology\u003c/p\u003e\n\u003cp\u003eErwan Hamon: Investigation, Methodology\u003c/p\u003e\n\u003cp\u003eChristophe Maillard: Methodology\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThe authors are grateful to Sarah Baghdadi (CEA/ MAR/DES/DMRC/SASP/LAAT) for its technical help and advice on the present paper and to Vincent Dalier (CEA/ MAR/DES/DMRC/SASP/LAAT), Sophie Gracia, Ang\u0026eacute;lique Ga\u0026iuml;do and Xavier Heres (CEA/MAR/DES/DMRC/SPTC/LCIS) for their help with ICP MS and ICP OES measurements.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eSong P, Wang J, Zhang Y, Lu H, Ren T (2019) Total evaporation technique for high-accuracy isotopic analysis of isotopically enriched molybdenum by negative thermal ionization mass spectrometry. 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J Radioanal Nucl Chem 1\u0026ndash;6. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s10967-017-5602-6\u003c/span\u003e\u003cspan address=\"10.1007/s10967-017-5602-6\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Separation, TIMS, Molybdenum, Uncertainty evaluation, isotope ratio","lastPublishedDoi":"10.21203/rs.3.rs-7748563/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7748563/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis paper describes a protocol combining resin separations and thermal ionization mass spectrometry measurements to analyze the molybdenum isotopic composition of nuclear samples in glove box condition. The development of two separation protocols was undertaken in the absence of HCl, known to lead to issues in glove boxes conditions. The first one is the purification of Mo from Zr and Ru through the implementation of a single-stage separation process, utilizing the TEVA resin. The second one combines a separation using UTEVA and TEVA resins to purify Zr and Mo if both element isotope abundance must be analyzed. For both protocols, the recovery of the Mo was greater than 80%, and the decontamination factor of Mo in regard of Zr and Ru was greater than 700. The measurement of Mo isotope ratios on a purified Mo sample exhibited no statistically significant deviation from the reference values. The study of the main contributors to the isotope ratio uncertainties showed that: a reduction of the uncertainty of the certified value of the \u003csup\u003e98\u003c/sup\u003eMo isotope abundance is needed to improve the accuracy of the measurement using the internal normalization and a better measurement repeatability is needed to improve the uncertainty of the isotope ratios corrected using an external normalization. Then, the developed protocols were then successfully applied to three nuclear samples. The relative uncertainties of the isotope abundances of the main isotopes were estimated to be less than 1%.\u003c/p\u003e","manuscriptTitle":"Determination of molybdenum isotope abundances and ratios for nuclear samples analysis using Thermal Ionization Mass Spectrometry","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-17 12:01:56","doi":"10.21203/rs.3.rs-7748563/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"af3a523f-7b18-4fd3-aaf2-42597a94cd48","owner":[],"postedDate":"October 17th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-12-22T16:06:38+00:00","versionOfRecord":{"articleIdentity":"rs-7748563","link":"https://doi.org/10.1007/s10967-025-10656-4","journal":{"identity":"journal-of-radioanalytical-and-nuclear-chemistry","isVorOnly":false,"title":"Journal of Radioanalytical and Nuclear Chemistry"},"publishedOn":"2025-12-19 15:58:29","publishedOnDateReadable":"December 19th, 2025"},"versionCreatedAt":"2025-10-17 12:01:56","video":"","vorDoi":"10.1007/s10967-025-10656-4","vorDoiUrl":"https://doi.org/10.1007/s10967-025-10656-4","workflowStages":[]},"version":"v1","identity":"rs-7748563","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7748563","identity":"rs-7748563","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}