Year
2008
Abstract
The IAEA, the facility operator and the national safeguards laboratory in Japan (Nuclear Material Control Center, NMCC) currently use a mixed U-Pu Large Size Dried (LSD) spike for U and Pu assay determination on common spent fuel samples taken from the input accountancy tank in the Tokai Reprocessing Plant (TRP), Japan. The IAEA LSD spike, implemented at TRP in 1990, consists of nominally 2 mg of 98% 239Pu and 40 mg of 19% 235U. The composition and size of the IAEA LSD spike was designed to be used on high burn-up fuel with U and Pu concentrations of about 170 and 1.3 g/L, respectively, and a sample size of 1 mL. The IAEA Safeguards Analytical Laboratory (SAL) produces approximately 500 LSD spikes annually for joint use by IAEA and NMCC inspectors at TRP, as well as for the On-Site Laboratory (OSL) at the Rokkasho Reprocessing Plant (RRP). The Institute for Reference Materials and Measurements (IRMM) in Geel supplies 700-1000 LSD spikes annually to Japan Nuclear Fuel, Ltd. (JNFL), the operator of RRP. The long-term application of the IRMM LSD spike for input samples at RRP and for assay of samples from the planned MOX facility at Rokkasho (JMOX) has been recently considered. JNFL estimates a supply of ~5000 LSD spikes annually to cover the demand of both facilities at full operational status. Reference material suppliers in Europe and the United States have expressed increasing concern about this strategy because low burn-up 239Pu has become ever more difficult to secure, characterize and ship as primary reference material. Examination of the analytical requirements for RRP indicates that the use of a secondary Pu reference material would provide sufficiently low uncertainty for safeguards purposes if used as a component of a mixed U-Pu spike. Accordingly, JNFL and the Japan Atomic Energy Agency (JAEA) have launched an initiative to certify an indigenous plutonium source as a secondary reference material for spiking at RRP and JMOX. International cooperation with SAL, IRMM, and laboratories in the USA will provide analytical support and external measurements.