Quantification of the Imperfectness of the Molecular Flow Conditions of the Gas Entering the Mass Spectrometer Ion Source for Ionization: Exemplified for CO2 Isotope Amount Ratio Measurements

A new model to describe the gas flow status inside the gas mass spectrometer (MAT 271) inlet system has been developed and applied to the latest isotope amount ratio measurements.JRC.D.4-Isotope measurement

Preparation and Certification of IRMM-075

A set of 6 new synthetic mixtures with n(236U)/n(238U) isotope ratios varying from 10-4 to 10-9 has been prepared and certified. Natural uranium with low 236U isotope abundance and enriched 236U were both purified using well proven chemical methodology extensively tested in the preparation of other uranium synthetic mixtures such as IRMM-074. The purification involved separation on anion and cation columns followed by precipitation as peroxide. Manipulations were carried out in separate new glove-boxes to avoid cross contamination. The oxides were sintered into U3O8 in an oven installed in a glove-box with controlled humidity. Primary solutions of the same concentration were prepared by dissolving the oxides of 236U and natU. From the 236U solution four dilutions were made by weighing. Weighed amounts of the dilutions of 236U and weighed amounts of natU were mixed to form a set of 236U/238U mixtures at a concentration of 1 mg U*g-1. The final solutions were dispensed into quartz ampoules which were subsequently flame sealed. Verification of the mixtures IRMM-075/1-7 was performed by TRITON TIMS measurements using Faraday collectors and secondary electron multiplier in combination with an RPQ energy filter for improved abundance sensitivity. The results agreed well with the certified values obtained from the mixing calculations. The uncertainties contributing to the final uncertainties of the isotopic ratios are the weighing errors, the measured impurities in each starting material, the stoichiometry of the oxides and the isotopic abundances of each. The method for the preparation and mixing are described and the certification and verification procedures are reported.JRC.D.4-Isotope measurement

Certification Report of EQRAIN Plutonium - Program N° 10

The EQRAIN Plutonium N° 10 is an evaluation program set up by CEA/CETAMA in order to evaluate the quality of results from nuclear measurement laboratories. The objective of this programme is to determine the plutonium concentration of a plutonium nitrate solution. Three ampoules were sent to each participant. At the IM/nuclear group, it was decided to analyse both of the EQRAIN N° 10 samples, H53 and H91. The results of this exercise would possibly enable us to identify problems occuring during the handling and measurements by mass spectrometric isotope dilution analysis (IDMS) of Pu. The evaluation of the mass-spectrometry analysis as part of this program could indicate unexplained processes such as the behaviour of the fractionation factor and outlier results not identified during measurements.JRC.D.4-Isotope measurement

Update on REIMEP-15: Isotopic Ratios of uranium in UF6

The REIMEP (Regular European Interlaboratory Measurement Evaluation Programme) campaign 15 for isotopic ratios of uranium in UF6 samples has been completed in 2002. The participants received 4 samples of low-enriched or slightly depleted uranium in the form of UF6 in standard monel capsules. The samples were prepared at IRMM by mixing uranium reference materials certified by gas mass-spectrometry in the form of UF6. The minor isotopes, 234U and 236U were certified at IRMM by Thermal Isotope Mass-spectrometry (TIMS) using a MAT262-RPQ mass spectrometer in ion counting mode. Certified values were sent to the participating laboratories immediately after receiving their measured results. The measured results and their comparison with the certified values allowed an overall view of the analytical capability in the nuclear field to measure uranium isotopic ratios in UF6 samples. However, for the so-called minor ratio 234U.238U the comparison of IRMM¿s certified values with all the participants results showed a significant relative deviation of about 2%, which is by far larger than the typical uncertainties expected for this kind of measurements. This significant deviation was considered disappointing for IRMM as the leading European nuclear safeguards metrology institute. This problem has now overcome first by measurements using the new TRITON TIMS at IRMM and second by a thorough investigation on the reasons for the deviation observed in the past.JRC.D.4-Isotope measurement

Preparation and Certification of the Isotopic Reference Material IRMM-049d

A highly enriched 242Pu Isotopic Reference Material (IRMM-049d) has been prepared and certified for the 242Pu isotope amount content. The certified value of 3.666 8(18) x 10-7 mol 242Pu per g of solution was established by Isotope Dilution Mass Spectrometry (IDMS). The plutonium isotopic composition was determined by Thermal Ionization Mass Spectrometry (TIMS) and calibration of these measurements by means of synthetic mixtures. The IRMM-049d Isotopic Reference Material is supplied in a glass ampoule with a screw cap seals containing about 10 mL of 5 mol x L-1 nitric acid with plutonium. The content of each vial is approximately 1 mg 242Pu. This Isotopic Reference Material is the product of a systematic IRMM programme to supply Isotopic Reference Materials of various isotopes at different concentrations.JRC.D.2-Reference material

Preparation and Certification of IRMM-3636, IRMM-3636a and IRMM-3636b

Isotope reference materials IRMM-3636 was prepared by gravimetrically mixing of solutions from highly enriched 99.96% 233U (IRMM-3630) and highly enriched 99.97% 236U (IRMM-3660) in order to obtain an isotopic ratio n(233U)/n(236U) close to unity. IRMM-3636a and IRMM-3636b were prepared from IRMM-3636 by gravimetrical dilution. The primary solution, IRMM-3636 is for the time being not yet available for external users. The certified isotope content values for IRMM-3636a of 4.27988(54)*10-7 mol U per g of solution and for IRMM-3636b of 2.21802(61)*10-8 mol U per g of solution and the certified isotope amount ratios have been established by mass metrology, subsequently the primary solution IRMM-3636 was verified by isotope mass spectrometry. The methodology used in the preparation and certification was similar to that of comparable uranium mixtures made in the past. The uncertainties contributing to the final uncertainties of the isotopic ratios are the weighing errors, the measured impurities in each starting material, the stoichiometry of the oxides and the isotopic abundances of each of the starting materials. The method for the preparation and mixing is described and the certification and verification procedures are reported. Verification of IRMM-3636 was performed by TRITON TIMS measurements using Faraday collectors and secondary electron multiplier in combination with an RPQ energy filter for improved abundance sensitivity. The results agreed well with the certified values obtained from the mixing calculations. By mixing the n(233U)/n(236U) double spike with a sample and applying internal mass fractionation correction, the n(235U)/n(238U) ratio of a given sample can be determined with the highest possible accuracy. The Isotopic Reference Materials IRMM-3636, IRMM-3636a and IRMM-3636b are part of a systematic IRMM programme to supply Isotopic Reference Materials of various isotopes at different concentrations. The Isotopic Reference Material is supplied in a sealed quartz ampoule containing 1 mL of a 1 M nitric acid solution.JRC.D.4-Isotope measurement

Preparation and Certification of IRMM-1027j, Large-Sized Dried (LSD) Spike

A new set of Large Size Dried (LSD) Spikes for the determination of uranium and plutonium by isotope dilution mass spectrometry in solutions of spent fuel from reprocessing plants has been prepared and certified for uranium and plutonium isotopic contents. The methodology followed was similar to that of previous batches. The solution, made by dissolution of the starting materials in nitric acid, was dispensed directly into individual penicillin vials. This new batch of large size dried spikes contains ca. 50 mg of uranium (235U abundance = 19.7%) and ca. 1.8 mg of plutonium (239Pu abundance = 97.8%) in each individual vial, covered with a light layer of organic material (cellulose acetate butyrate) as stabilizer. The U and Pu amount content was certified based on values from mass metrology. Verification of the amount contents of the spike was done by IDMS at IRMM. The values measured for the batch solution and of the dried covered spikes agreed well with those calculated from the weights of starting materials dissolved and the weights of the final solution.JRC.D.4-Isotope measurement

Preparation and Verification of QUAD Uranium Isotopic Reference Material IRMM-3100a

The isotopic reference material IRMM-3100a was prepared by gravimetrical dilution of IRMM-3101. The primary solution IRMM-3101 was designed such that the material consists of equivalent parts of four individual isotopes n(233U)/n(235U)/n(236U)/n(238U) with a ratio of one. The certified isotope amount ratio for ratio n(233U)/n(236U) has been established by mass metrology and was verified by isotope mass spectrometry. The certified ratios n(234U)/n(236U), n(235U)/n(236U) and n(238U)/n(236U) have been measured by TIMS in multi-dynamic mode and using the n(233U)/n(236U) ratio for internal normalization. The preparation of IRMM-3101 is in full described elsewhere. [1] The Isotopic Reference Material IRMM-3100a is part of a systematic IRMM programme to supply Isotopic Reference Materials of various isotopes at different concentrations. The Isotopic Reference Material is supplied in a quartz ampoule containing 0.5 mL of a 1 M nitric acid solution.JRC.DG.D.2-Reference material

Preparation and Certification of IRMM-1027k, Large-Sized Dried (LSD) Spike

The concept of directly spiking samples of the solution with dissolved irradiated nuclear fuel for later dilution and measurement of the isotopic contents of uranium and plutonium has been developed successfully. Large sized dried spikes (LSD) have become a fundamental part of the fissile material control of irradiated nuclear fuel. In the frame of providing these spikes to the nuclear industry, a new set of LSD Spikes for the determination of uranium and plutonium by isotope dilution mass spectrometry in solutions of spent fuel from reprocessing plants has been prepared and certified for uranium and plutonium isotopic contents. The methodology followed was comparable to that of previous batches. The solution, made by dissolution of the starting materials in nitric acid, was dispensed directly into individual penicillin vials. However in this campaign an automated system was introduced to dispense and weigh the majority of vials. At the same time the system was validated by comparing the results with those of the traditional syringe dispensing and substitution weighing. This new batch of large size dried spikes contains ca. 50 mg of uranium (235U abundance = 19.1%) and ca. 1.8 mg of plutonium (239Pu abundance = 97.8%) in each individual vial, covered with a light layer of organic material (cellulose acetate butyrate) as stabilizer. The U and Pu amount content was certified based on values from mass metrology of the validated automated system or from the manual weighings. Verification of the amount contents of the spike was done by IDMS at IRMM. The values measured for the batch solution and of the dried covered spikes agreed well with those calculated from the weights of starting materials dissolved and the weights of the final solution.JRC.D.4-Isotope measurement