CONCEPTUAL DESIGNS OF NDA INSTRUMENTS FOR THE NRTA SYSTEM AT THE ROKKASHO REPROCESSING PLANT*

We are studying conceptual designs of selected nondestructive assay (NDA) instruments for the near-real-time accounting system at the Rokkasho Reprocessing Plant (RRP) of Japan Nuclear Fuel Limited (JNFL). The JNFL RRP is a large-scale commercial reprocessing facility for spent fuel from boiling-water and pressurized- water reactors. The facility comprises two major components: the main process area to separate and produce purified plutonium nitrate and uranyl nitrate from irradiated reactor spent fuels, and the co-denigration process area to combine and convert the plutonium nitrate and uranyl nitrate into mixed oxide (MOX). The selected NDA instruments for conceptual design studies are the MOX-product canister counter, holdup measurement systems for calcination and reduction furnaces and for blenders in the co-denigration process, the isotope dilution gamma-ray spectrometer for the spent fuel dissolver solution, and unattended verification systems. For more effective and practical safeguards and material control and accounting at RRP, we are also studying the conceptual design for the U03 large-barrel counter. This paper discusses the state-of-the-art NDA conceptual design and research and development activities for the above instruments.