The performance of the 30-Gallon-Drum Neutron Multiplicity Counter at Rocky Flats Environmental Technology Site

In the fall of 1994, Rocky Flats Environmental Technology Site (RFETS) committed to offering approximately one metric ton of excess weapons plutonium for safeguards verification by the International Atomic Energy Agency (IAEA). At that time RFETS decided to offer cans of plutonium of varying purity, stored one or two to a package in 10- gal. drums, and contracted with the Los Alamos to obtain a 30-Gallon- Drum Neutron Multiplicity Counter (NMC) to measure these materials. A multiplicity counter was deemed necessary because of IAEA experience that the standard coincidence counting techniques routinely used in IAEA inspections would fail for plutonium-bearing materials of variable purity. RFETS also thought that such an instrument would be useful for their domestic safeguards needs