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

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

Neutron-induced Fission Cross Section of240,242Pu

A sensitivity analysis for the new generation of fast reactors [Salvatores (2008)] has shown the importance of improved cross section data for several actinides. Among them, the240,242Pu(n,f) cross sections require an accuracy improvement to 1-3% and 3-5%, respectively, from the current level of 6% and 20%. At the Van de Graaff facility of the Institute for Reference Materials and Measurements (JRC-IRMM) the fission cross section of the two isotopes was measured relative to two secondary standard reactions,237Np(n,f) and238U(n,f), using a twin Frisch-grid ionization chamber. The secondary standard reactions were benchmarked through measurements against the primary standard reaction235U(n,f) in the same geometry. Sample masses were determined by means of low-geometry alpha counting or/and a 2p Frisch-grid ionization chamber, with an uncertainty lower than 2%. The neutron flux and the impact of scattering from material between source and target was examined, the largest effect having been found in cross section ratio measurements between a fissile and a fertile isotope. Our240,242Pu(n,f) cross sections are in agreement with previous experimental results and slightly lower than present evaluations. In case of the242Pu(n,f) reaction no evidence for a resonance at En=1.1 MeV was found.Postprint (published version

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

Towards high accurate neutron-induced fission cross sections of 240,242Pu: Spontaneous fission half-lives

Fast spectrum neutron-induced fission cross sections of transuranic isotopes are being of special demand in order to provide accurate data for the new GEN-IV nuclear power plants. To minimize the uncertainties on these measurements accurate data on spontaneous fission half-lives and detector efficiencies are a key point. High -active actinides need special attention since the misinterpretation of detector signals can lead to low efficiency values or underestimation in fission fragment detection. In that context, 240,242Pu isotopes have been studied by means of a Twin Frisch-Grid Ionization Chamber (TFGIC) for measurements of their neutron-induced fission cross section. Gases with different drift velocities have been used, namely P10 and CH4. The detector efficiencies for both samples have been determined and improved spontaneous fission half-life values were obtained.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

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

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

Large-sized dried spikes (LSD) have become a fundamental part of the fissile material control of irradiated nuclear fuel. Within the programme at IRMM to provide these spikes to the nuclear industry and the safeguards¿ inspectorate, a new set of LSD Spikes for the determination of uranium and plutonium by isotope dilution mass spectrometry (IDMS) 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. An automated system was used to dispense and weigh the vials. The new batch of large size dried spikes contains ca. 50 mg of uranium with a 235U amount fraction of 19.5% and ca. 1.8 mg of plutonium with a 239Pu amount fraction of 97.8% in each individual vial, covered with a light layer of organic material (cellulose acetate butyrate) as stabilizer. The U amount content was certified based on values from mass metrology of the validated automated system. Verification of the U amount contents of the spike was done by IDMS at IRMM. The values measured for the dried covered spikes agreed well with those calculated from the masses of starting materials dissolved and the masses of the final solution. The Pu amount content was certified by using IDMS.JRC.DG.D.2-Reference material