The Epithermal neutron multiplicity counter at Hanford

The Epithermal Neutron Multiplicity Counter (ENMC) and the associated Advanced Multiplicity Shift register (AMSR) electronics package, developed at Los Alamos under the US Department of Energy (DOE) Office of Safeguards and Security Technology Development Program, was evaluated at the Hanford Plutonium Finishing Plant earlier this year. Initial demonstration measurements involved Hanford facility personnel and two International Atomic Energy Agency (IAEA) inspectors who measured selected IAEA standards and items the IAEA had experienced problems with previously. Items were measured in the ENMC and also in the Plutonium Scrap Multiplicity Counter (PSMC), which belongs to the IAEA but is also used by the facility. Each item was measured for 15 minutes. The Pu mass ranged from 250 to 1700 g. Alpha (the ratio of alpha, n to spontaneous fission neutrons) ranged from 0.5 to {approx}15. In all cases, the precision of the ENMC measurements was far superior to that of the PSMC and provided 8.3 to 42.5 faster measurements, with the larger factors coming from the high-alpha items. The seven IAEA standards had alpha values ranging from 0.5 to 13, and the average bias was 0.75% with a standard deviation of 3.18% for the ENMC. The mean bias for the PSMC measurements more » is 4.02% with a standard deviation of 8.27%. In addition, the ENMC was used to assay 17 process residues with alpha values ranging from 2 to 20. The facility and the IAEA were impressed with the performance of the ENMC, and the facility is attempting to procure a unit for its use. The IAEA would also like to use the ENMC for its inspections once the facility has acquired the device. « less