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

An Inter-Calibration Campaign Using Various Selected Pu Spike Isotopic Reference Materials

In nuclear safeguards, precise and accurate isotopic analyses are needed for two major elements from the nuclear fuel cycle: uranium and plutonium. This can be achieved by Isotope Dilution Mass Spectrometry (IDMS), which is one of the most reliable analytical techniques for the determination of plutonium amount content to a high level of accuracy. In order to achieve reliable isotope measurements isotopic reference materials with certified amount of plutonium and isotopic composition are required. At the Institute for Reference Materials and Measurements (IRMM) various plutonium spike reference materials for isotopes 239Pu, 240Pu and 244Pu are available. This enabled the setup of an inter-calibration campaign inter-linking selected plutonium spikes on a metrological basis applying state-of-the-art measurement procedures. The aim of this campaign is threefold: firstly to perform measurements on selected plutonium spike isotopic reference materials for quality control purposes, secondly to verify the amount content and the isotopic composition of the recently produced IRMM-1027m Large Sized Dried (LSD) spikes and thirdly to demonstrate IRMM's measurement capabilities for plutonium analysis via external quality tools. The obtained results using various spikes isotopic reference materials will be presented and discussed in this paper. The measurement uncertainties of the IDMS results were calculated according to the Guide to the Expression of Uncertainty in Measurement (GUM)JRC.D.2-Reference material