Installation and calibration of the oversized low-level package counter at Los Alamos National Laboratory

With the importance of safeguards in production facilities, the Los Alamos National Laboratory Plutonium Facility has installed a neutron slab counter to facilitate the measurement of low-level waste packaged in 4 ft {times} 4 ft {times} 8 ft crates. In the past, oversized packages were measured by a gamma technique to assess holdup. The measurement was time-consuming and cumbersome, and the efficiency was questionable. The slab counter has alleviated the time and efficiency problems of the gamma measurement. The counter consists of four slab counters, each slab containing twenty 60-in. long helium-3 tubes embedded in 3.5 in. thick polyethylene slab. The detectors are shielded from room background by an additional 3.5 in. of polyethylene. The 4 ft 6 in. by 7 ft 6 in by 8 in. steel encased slabs are arranged around a 4 ft 6 in. {times} 22 ft conveyor system with two slabs on each side of the conveyor. The slabs are located on one end of the conveyor, with the end open to facilitate waste crate loading by forklift. The system was calibrated with a {sup 252}Cf source and placed in various locations throughout a mock waste crate. The mock calibration waste crate can be loadedmore » with waste material to simulate waste crates generated in the facility.« less