Status of in-plant neutron coincidence counting

Neutron coincidence counters are used in nuclear material processing plants to assay bulk quantities of plutonium or uranium. Passive assays of plutonium are often made with the High-Level Neutron Counter (HLNC or HLNC-II), the Dual-Range Coincidence Counter, or customized detector geometries. Active assays of uranium are often made with the Active Well Coincidence Counter or the Uranium Neutron Coincidence Collar. Modern counters may have flattened efficiency profiles, fast AMPTEK amplifier/discriminators mounted directly next to the /sup 3/He detection tubes, external background shields, or special sample-loading mechanisms. Typical counting times and accuracies that can be obtained for plutonium are summarized. If isotopic composition is known, large plutonium samples can be assayed in 100 to 200 s - comparable to the time requires to input sample data into the counter's calculator or computer.