Year
1999
Abstract
We have developed 3He tubes with high pressure to improve the performance of active and passive neutron counters used for safeguards and nuclear material control. Neutron coincidence counting requires both high efficiency and short neutron die-away time. In cooperation with G. E. Reuter- Stokes, we have developed lo-atm 3He tubes to give up to an order of magnitude performance improvement compared with conventional 4-atm tubes. Conventional neutron counters such as the active well coincidence counter (AWCC) and the neutron collar (UNCL) can be retrofitted with the lo-atm tubes resulting in a factor of 2 reduction in the measurement time to reach a given precision. We have designed optimized counters for small samples with an absolute efficiency of 79% and die- away time of 20 us. The statistical error for multiplicity counting is reduced so that the measurement time is reduced by up to a factor of 10 for impure plutonium samples. Large neutron waste counters for drums and crates have been designed using the lo-atm tubes to give an efficiency of 40% and to make multiplicity counting practical for the large waste samples.