ASSAY OF SCRAP PLUTONIUM OXIDE BY THERMAL NEUTRON MULTIPLICITY COUNTING FOR IAEA VERIFICATION OF EXCESS MATERIALS FROM NUCLEAR WEAPONS PRODUCTION*

The US Nonproliferation and Export Control Policy commits the US to placing under International Atomic Energy Agency (IAEA) safeguards excess nuclear materials no longer needed for the US nuclear deterrent. As of January 1, 1996, the IAEA has completed Initial Physical Inventory Verification (IPIV) at the Oak Ridge Y-12 plant, the Hanford Plutonium Finishing Plant, and a plutonium storage vault at Rocky Flats. Two IPIVS W= performed at Hanford: one in December 1994 and one in August 1995. This paper reports the results of thermal neutron multiplicity assay of plutonium residues during the seeond IPIV at Hanfond. Using the Three Ring Multiplicity Counter (3RMC), measurements were performed on 69 individual cans of plutonium residues, each containing approximately 1 kg of material. Of the 69 items, 67 passed the IAEA acceptance criteria and two we~ selczted for destructive analysis.