Results of the REIMEP-17 interlaboratory comparison for the measurement of the U and Pu amount content and isotope amount ratios in the synthetic dissolved spent nuclear fuel solution

Reliable measurements are needed for the verification measures of States’ declarations of their nuclear activities in line with international agreements and the EURATOM Treaty. Laboratories carrying out measurements of nuclear material need to follow stringent quality control concepts and are required to demonstrate their measurement capabilities on a regular and timely basis to legal and Safeguards authorities. This includes participation in interlaboratory comparisons (ILCs). In the frame of the Regular European Interlaboratory Measurement Evaluation Programme (REIMEP) a new ILC (REIMEP-17) was jointly organized by the EC-Joint Research Centre-Institute for Reference Materials and Measurements (JRC-IRMM) and EC-Joint Research Centre-Institute for Transuranium Elements (JRC-ITU) for EURATOM and IAEA safeguards laboratories, nuclear plant operators and nuclear material laboratories. The focus in REIMEP-17 was on measurements of the uranium and plutonium amount contents, and isotope amount ratios in synthetic input solutions. Participants received two test samples, REIMEP-17A and REIMEP 17B, with different uranium and plutonium amount contents. Laboratories were requested to report the results with associated uncertainties applying their standard measurement procedures, and had the possibility to benchmark those results against the independent assigned (reference) values and the International Target Values for Measurement Uncertainties in Safeguarding Nuclear Materials (ITV2010). It can be concluded that the participants in REIMEP-17 performed well for the measurements of uranium and plutonium amount content in compliance with the respective ITV2010. In particular, the measurement performance for the isotope amount ratios was very satisfactory for both REIMEP-17 test samples. This confirms the measurement capabilities of laboratories in the field of nuclear material analysis and demonstrates that the stringent ITV2010 are achievable target values under state-of-practice conditions. On the other hand, the spread of results for the minor uranium isotope amount ratios was larger. Moreover, for some of the measurands, differences in the measurement uncertainty estimations provided by laboratories were observed even when using the same instrumental technique. A summary of the participant results is presented and discussed in this paper.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

NUSIMEP-8: Uranium and plutonium isotope amount ratios in low-level synthetic nitrate solution - Inter-laboratory comparison, Report to participants

The Additional Protocol (AP) authorizes safeguards authorities to verify the absence of undeclared nuclear activities in all parts of a state’s nuclear fuel cycle as well as any other location where nuclear material is or may be present. As a part of the Additional Protocol, environmental sampling has become an important tool for the detection of non-declared nuclear activities. In environmental sampling, swipe samples are collected for bulk and particle analysis. Considering the potential consequences of the analyses, these measurements need to be subjected to a rigorous quality management system. The Nuclear Signatures Inter-laboratory Measurement Evaluation Programme (NUSIMEP) was established in 1996 to support the growing need to trace and measure the isotopic abundances of elements characteristic for the nuclear fuel cycle present in trace amounts in the environment. NUSIMEP-8 focused on measurements of low-level uranium and plutonium in synthetic nitrate solution aiming to support EURATOM safeguards (DG ENER), the IAEA Network of Analytical Laboratories (NWAL) for bulk analysis of environmental samples and laboratories in the field. The NUSIMEP-8 solution was prepared from mixed oxide fuel dissolved in nitric acid with addition of natural uranium and diluted to an environmental level. Participating laboratories in NUSIMEP-8 received one sample solution with undisclosed values of n(238Pu)/n(239Pu), n(240Pu)/n(239Pu), n(241Pu)/n(239Pu), n(242Pu)/n(239Pu) and n(234U)/n(238U), n(235U)/n(238U), n(236U)/n(238U) amount ratios. Those isotope amount ratios were measured by participating laboratories using their routine analytical procedures. Measurement of the major isotope ratios n(235U)/n(238U) and n(240Pu)/n(239Pu) were obligatory; measurement of the minor isotope ratios were optional. 25 laboratories registered for NUSIMEP-8, three withdrew the registration while one laboratory encountered problems with the shipment of the sample. Finally, 19 participants have reported measurement results using different analytical techniques, among those 10 NWAL laboratories. Two participants did not report their results due to technical problems. The participant measurement results have been evaluated against the certified reference values by means of z-scores and zeta-scores in compliance with ISO 13528:2005. The NUSIMEP-8 results were overall satisfactory and in compliance with the IAEA Measurement Quality Goals for the analysis of bulk environmental samples. This report presents the NUSIMEP-8 participant results; including the evaluation of the questionnaire. In addition feedback from the measurement communities in nuclear safeguards, nuclear security and environmental sciences was collected in view of identifying future needs for NUSIMEP inter-laboratory comparisons.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Results of the REIMEP-17 and NUSIMEP-8 inter-laboratory comparisons

Confidence in measurement results is established via reference materials, reference measurements and inter-laboratory comparisons. The Institute for Reference Materials and Measurements of the Joint Research Centre of the European Commission (EC-JRC-IRMM) has a long time experience in the development of nuclear isotopic reference materials and in the organisation of inter-laboratory comparisons (ILCs) in compliance with the respective international ISO guides. The Regular European Inter-laboratory measurement Evaluation Programme (REIMEP) was established at IRMM in 1982 for carrying out external quality control of the measurements for the elements characteristic of the nuclear fuel cycle, while the Nuclear Signatures Inter-laboratory Measurement Evaluation Programme (NUSIMEP) aims to provide test samples for the measurement of trace amounts of nuclear material in environmental matrices. Participants in REIMEP/NUSIMEP can benchmark their measurement results against independent and traceable reference values, assessing their measurement capabilities in line with international or national quality goals. The REIMEP-17 and NUSIMEP-8 certified test samples were prepared from dissolution of mixed oxide fuel in nitric acid and addition of natural uranium. In REIMEP-17 laboratories received two test samples with undisclosed values of the U, Pu amount content and U and Pu isotope amount ratios. The certified test sample REIMEP-17A had a concentration typical for undiluted input solution whereas REIMEP 17B was a diluted fraction thereof. The NUSIMEP-8 certified test sample was prepared by further gravimetrical dilution of REIMEP-17B. Measurement of the n(235U)/n(238U) and n(240Pu)/n(239Pu) ratios were obligatory while the measurement of other ratios were optional. Laboratories were asked to apply their routine analytical procedures and report the results with associated measurement uncertainty. The participant results have been evaluated against the independent certified reference value by means of z and zeta scores in compliance with ISO 13528:2005. In general, the REIMEP-17 results were satisfactory and in compliance with the International Target Values for Measurement Uncertainties in Safeguarding Nuclear Materials (ITV2010). The NUSIMEP-8 results were overall satisfactory and met the International Atomic Energy Agency Measurement Quality Goals (IAEA-SGAS-QC) for the analysis of bulk environmental samples.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

REIMEP-17: Plutonium and uranium amount content, and isotope amount ratios in synthetic input solution - Inter-laboratory comparison, Report to participants

Nuclear safeguards is based on international agreements and in the EU has the rank of European law (Euratom Treaty, Chapter VII, Euratom regulation 302/2005) ensuring that materials usable in both peaceful and military applications – such as uranium and plutonium – are used for peaceful purposes only. Physical verification measurements at nuclear facilities, such as reprocessing and fuel fabrication plants, are a part of safeguards inspections. The reliability of measurement results in nuclear material accountancy and verification is indispensable for an effective safeguards system. A new external quality control campaign, REIMEP-17 on "Plutonium and uranium amount content, and isotope amount ratios in synthetic input solution" was organised by JRC-IRMM in cooperation with JRC-ITU, particularly for EURATOM safeguards (DG ENER) laboratories and the IAEA Network of Analytical Laboratories for nuclear material analysis (IAEA-NWAL), as well as for laboratories from industry and experts in the field. Participating laboratories in REIMEP-17 received two samples with undisclosed U, Pu amount content and n(238Pu)/n(239Pu), n(240Pu)/n(239Pu), n(241Pu)/n(239Pu) n(242Pu)/n(239Pu) and n(234U)/n(238U), n(235U)/n(238U), n(236U)/n(238U) amount ratio values. One of the samples, REIMEP 17A had uranium and plutonium amount contents typical for undiluted spent nuclear fuel input solution and the other sample, REIMEP-17B was a diluted fraction of it. The participants were requested to apply their standard analytical procedures and report the results with the associated uncertainties. The laboratories were also requested to complete and return a questionnaire so that an overall picture of the laboratories’ capabilities could be made. REIMEP-17 was announced to participants in April 2012. Sixteen laboratories registered for REIMEP 17. Due to delays in the shipment of the samples and problems with the transport containers, three laboratories were not able to receive the samples. Three laboratories withdrew their participation. Consequently, the deadline for submitting the results had to be extended until July 1, 2013. In the end JRC-IRMM received results from nine laboratories; one laboratory did not submit the results. The reported measurement results have been evaluated against the independent reference values by means of z-scores and zeta-scores in compliance with international guidelines. In general the REIMEP-17 participants' results were satisfactory and in compliance with the International Target Values for Measurement Uncertainties in Safeguarding Nuclear Materials (ITV2010). This report presents the REIMEP-17 participants' results; including the evaluation of the questionnaire.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

CERTIFICATION REPORT: Preparation and Certification of Large-Sized Dried (LSD) Spike - IRMM-1027q

IRMM Large-Sized Dried (LSD) Spikes are widely used as a fundamental part of the fissile material control of irradiated nuclear fuel and have been provided on a regular basis to safeguards authorities and industry for more than 10 years. This report describes the preparation and certification of a new batch of LSD Spikes. IRMM-1027q is a dried nitrate material in cellulose acetate butyrate (CAB), certified for the mass of uranium and plutonium and isotope amount ratios per unit. The material was produced following ISO Guide 34:2009. The certified reference materials uranium metal EC NRM 101, enriched uranium metal NBL CRM 116-A and plutonium metal CETAMA MP2 were used as starting materials to prepare the mother solution. This solution was dispensed by means of an automated robot system into individual units and dried down. A solution of an organic substance, cellulose acetate butyrate (CAB), was dried on the spike material as a stabiliser to retain the dried material at the bottom of the vial. Between unit-homogeneity was quantified and stability during dispatch and storage were assessed in accordance with ISO Guide 35:2006. The certified values for the uranium and plutonium isotope amount ratios and for the mass of uranium per unit were obtained from the gravimetric preparation of the mother solution, taking into account the mass, purity and isotopic abundances of the starting materials, the mass of the mother solution, and the mass of an aliquot in each individual unit. The certified values for the mass of plutonium per unit were established by isotope dilution thermal ionisation mass spectrometry (ID-TIMS). Confirmatory measurements were performed by isotope dilution thermal ionisation mass spectrometry (ID-TIMS) and thermal ionisation mass spectrometry (TIMS). Uncertainties of the certified values were estimated in compliance with the Guide to the Expression of Uncertainty in Measurement (GUM) and include uncertainties related to possible inhomogeneity and to characterisation. This spike CRM is applied as a calibrant to measure the uranium and plutonium amount content of dissolved spent nuclear fuel solutions using isotope dilution mass spectrometry (IDMS). Each unit contains about 55 mg of uranium with a relative mass fraction m(235U)/m(U) of 17.7 % and 1.9 mg of plutonium with a relative mass fraction m(239Pu)/m(Pu) of 97.8 % as dried nitrates in CAB. The whole amount of sample per unit has to be used for analysis.JRC.D.2-Standards for Innovation and sustainable Developmen

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

IRMM-1000a and IRMM-1000b: uranium reference materials certified for the production date based on the 230Th/234U radiochronometer Part II: Certification

The IRMM-1000a and IRMM-1000b uranium reference materials, of 20 mg uranium and 50 mg uranium, respectively, were produced by the European Commission Joint Research Centre’s Institute for Reference Materials and Measurements (EC-JRC-IRMM) in collaboration with the Institute for Transuranium Elements (EC-JRC-ITU). They are the first uranium reference materials certified for the production date based on the 230Th/234U radiochronometer, i.e. the date of the last chemical separation of these two radionuclides. Such certified reference materials (CRMs) are required for proper validation of measurement procedures in Nuclear Forensics in order to determine the "age" of uranium samples and to establish traceability of the measurement results to the SI. The certified reference value and its uncertainty, homogeneity and stability of the material were established in accordance with the ISO Guide 34:2009 and the 'Guide to the Expression of Uncertainty in Measurement'.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Preparation and certification of IRMM-1000a (20 mg) and IRMM-1000b (50 mg) - Certified uranium reference material for the production date

This report describes the development and certification of IRMM-1000a and IRMM-1000b, a uranium reference material certified for the production date based on the 230Th/234U radiochronometer. The certified value was assigned following ISO Guide 34:2009 [ ]. The starting material was low-enriched uranium with a relative mass fraction, m(235U)/m(U) of 3.6%. The chemical separation of the 230Th decay product from its parent nuclide 234U to the maximum extent of completeness was achieved. The certified production date was confirmed using the 230Th/234U radiochronometer, and corresponds to the last chemical separation, i.e. the removal of 230Th from the material to the maximum extent achievable. The between unit-homogeneity and the stability of the certified value were assessed in accordance with ISO Guide 35:2006 [ ]. The material was characterised by taking into account the date and time elapsed of the last chemical and complete separation of 230Th from 234U. The completeness of the separation was confirmed firstly by determining the U/Th separation factors and uranium recoveries using -ray spectrometry, and then by means of ICP-MS measurements using a 232Th tracer. After sufficient ingrowth of thorium into the characterised uranium reference material, measurements of the 234U and the 230Th amount contents were carried out by isotope dilution mass spectrometry (IDMS) in compliance with ISO/IEC 17025:2005 [ ]). Subsequently, the determined n(230Th)/n(234U) was used in the calculation to confirm the certified production date. The uncertainty of the certified value was estimated in compliance with the Guide to the Expression of Uncertainty in Measurement (GUM) [ ] and includes uncertainties related to characterisation, possible inhomogeneity and instability. The material is intended for calibration of methods, quality control, and assessment of method performance with isotope mass spectrometry and radiometry techniques. As any reference material, it can also be used for control charts or validation studies. The certified reference material is available in two sizes: 20 mg (IRMM-1000a) and 50 mg uranium (IRMM-1000b) as dried uranyl nitrate in screw-cap Teflon (PFA) vials. There is no minimum sample intake to be taken into account.JRC.D.2-Standards for Innovation and sustainable Developmen

Preparation and Certification of Large-Sized Dried (LSD) Spike – IRMM-1027s

Large-Sized Dried (LSD) spikes are used as a fundamental part of the fissile material control of irradiated nuclear fuel and have been provided on a regular basis to safeguards authorities and industry for more than 10 years. This report describes the preparation and certification of a new batch of LSD spikes. IRMM-1027s is a dried nitrate material in cellulose acetate butyrate (CAB), certified for the mass of uranium and plutonium and the uranium and plutonium isotope amount ratios per unit. The material was produced in compliance with ISO/IEC 17034:2016 and certified in accordance with ISO Guide 35:2006. The certified reference materials uranium metal EC NRM 101, enriched uranium metal NBL CRM 116-A and plutonium metal CETAMA MP2 were used as starting materials to prepare the mother solution. This solution was dispensed into individual units by means of an automated robot system and dried down. A solution of an organic substance, cellulose acetate butyrate (CAB) was dried on the spike material as a stabiliser to retain the dried material at the bottom of the vial. In total 950 units were produced. Between-unit homogeneity was quantified and stability during dispatch and storage were assessed in accordance with ISO Guide 35:2006. The certified values for the uranium and plutonium isotope amount ratios were obtained from the gravimetric preparation of the mother solution, taking into account the mass, purity and isotopic composition of the starting materials. The certified values for the mass of plutonium and uranium per unit were established by isotope dilution thermal ionisation mass spectrometry (ID-TIMS) on randomly selected units. External verification measurements were performed by isotope dilution mass spectrometry (IDMS) and thermal ionisation mass spectrometry (TIMS) on randomly selected units of IRMM-1027s. Uncertainties of the certified values were estimated in compliance with the Guide to the Expression of Uncertainty in Measurement (GUM) and include uncertainties related to possible inhomogeneity and to characterisation. The main purpose of this material is for use as a spike isotopic reference material to measure the plutonium and uranium amount content of spent nuclear fuel solutions using IDMS. Each unit contains about 55 mg of uranium with a relative mass fraction m(235U)/m(U) of 19.0 % and 1.7 mg of plutonium with a relative mass fraction m(239Pu)/m(Pu) of 97.8 % as dried nitrates in CAB. The whole amount of sample per unit has to be used for analysis.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

CERTIFICATION REPORT: Preparation and certification of a new batch of 242Pu spike: IRMM-049e

This report describes the preparation and certification of the 242Pu spike reference material IRMM-049e, applied for determination of plutonium content in nuclear materials by isotope dilution mass spectrometry (IDMS) in nuclear safeguards, nuclear security and in the industry. As the stock of IRMM-049d is close to exhaustion, it was decided to produce about 90 ampoules of a new spike certified reference material (CRM) IRMM-049e and, therefore to maintain the provision of the IRMM-049 series of spike CRMs. IRMM-049e is the first of the IRMM-049 series produced in compliance with ISO 17034:2016. The amount content of 242Pu in IRMM-049e was characterised on 10 randomly stratified selected units by Isotope Dilution – Thermal Ionisation Mass Spectrometry (ID-TIMS) using the IRMM-1027o CRM as a spike. The plutonium isotope amount ratios were measured using the same 10 selected units by TIMS. The material was finally certified for the amount content of 242Pu and the total Pu, the mass fractions of 242Pu and total Pu, the Pu isotope amount ratios as well as the plutonium isotope abundances as amount and mass fractions, and for the molar mass of Pu in IRMM-049e. The certified values were confirmed by ID-TIMS using the IRMM-086 (239Pu spike) and verified against the reference value of the external certified test sample Pu EQRAIN-13 provided by CEA/CETAMA. These verification studies were carried out in the frame of the on-going inter-calibration campaign using state-of-the art measurement procedures linking together different JRC plutonium spike reference materials and also external reference materials to underpin the confidence in the use of JRC isotopic plutonium reference materials for safeguards verification. Between unit-homogeneity was quantified in accordance with ISO Guide 35:2006. No stability study was performed for this reference material since the general behaviour of this material is well known from past experience. However, a post-certification stability monitoring will be done every two years to control its stability after issuance of the certificate. The uncertainties of the certified values were estimated in compliance with the Guide to the Expression of Uncertainty in Measurement (GUM) and include uncertainties related to characterisation and possible inhomogeneity. The main purpose of this material is for use as a spike isotopic reference material for quantification of plutonium in an unknown nuclear sample. IRMM-049e is supplied in a screw-cap glass ampoule containing 10 mL nitric acid solution (c = 5 mol/L) with a certified plutonium (total Pu) mass fraction of (91.52 ± 0.12) µg/g and a certified 242Pu amount content of (0.35828 ± 0.00045) µmol/g. Because the IRMM-049e material is a true solution and as such, can be regarded as completely homogeneous, there is no minimum sample intake to be taken into account for the analysis.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard