Title: Stabilisation of uranium/plutonium dried spikes with a cellulose matrix
Publisher: ESARDA
Publication Year: 2015
JRC N°: JRC95115
ISBN: 978-92-79-49495-6 (PDF)
ISSN: 1831-9424 (online)
URI: http://publications.jrc.ec.europa.eu/repository/handle/JRC95115
DOI: 10.2789/099293
Type: Articles in periodicals and books
Abstract: Large Scale Dried (LSD) spikes are used in nuclear safeguards laboratories world-wide for an accurate Isotope Dilution Mass Spectrometric (IDMS) determination of physical nuclear material inventories, with relative uncertainties for U and Pu of better than 0.28 % (k=1). IDMS fully relies on the mechanical integrity of the spikes. The spikes need to be robust during transport and storage for their guaranteed life-time of 3 years. Mechanically damaged spikes are no longer fit for purpose (ISO-guide 34 on "General requirements for the competence of reference material producers"). LSD spikes are produced by dispensing accurately-weighed quantities of a nuclear material reference solution into penicillin vials, after which the solution is evaporated to dryness. Some commercially available spikes are additionally covered with an organic coating to prevent unintented losses of nuclear material when the spike vials are opened for use. The main requirements for such coatings are good adherence to glass, mechanical stability, resistance to radiation and long term stability. Furthermore, the coating should readily dissolve in nitric acid and should not interfere with chromatographic chemical separation and subsequent mass spectrometric measurements. JRC-ITU carried out research and development to improve on traditional coatings based on Cellulose Acetate Butyrate (CAB) that is used in spikes such as JRC-IRMM 1027. CarboxyMethyl Cellulose Sodium Salt (CMC) is proposed as an alternative to current CAB coatings that fail to offer the desired shelf-life. In the JRC-ITU procedure, CMC is dissolved in water, changed to a nitrate form with a high viscosity and added to spike vials containing the dried deposits of nuclear reference material. After warming, the CMC forms foam that is extremely robust to mechanical impact and appears to have a long shelf-life. The CMC foam coatings were scrutinized by Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy (SEM/EDX) and preliminary IDMS studies indicate that CMC does not interfere with IDMS assays. CMC appears to be a promising coating material for LSD spikes.
JRC Directorate:Nuclear Safety and Security

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