Coincidence counter design for the assay of vitrified nuclear waste

For the termination of nuclear safeguards and transfers to waste storage, the verification of the plutonium content in vitrified nuclear waste is required by international safeguards agreements. A novel design has been used to develop a coincidence counter for measuring vitrified nuclear waste. The authors have devised a method to measure the 244Cm content and to calculate the plutonium content from the curium-to-plutonium ratio. In order to provide unattended inspection, the counter is designed for continuous operation in the presence of highly radioactive samples: 3.0 x 107 Rad/h gamma and 9.0 x 107/s neutron fluence. Operability under these conditions has been obtained by designing a heavily shielded detector with radiation hard components subtending a limited solid angle. A counting technique, Localized Source Term Coincidence Counting, has been developed to allow neutron assay of this type of sample. The system will be installed at the Power Nuclear Corporation Tokai Vitrification Facility in the later part of 1998