Waste Crate Counter Design

We have examined a number of scenarios for configuring slab counters to measure low-level, noncompactible plutonium-bearing waste (LLW) and waste destined for burial at the Waste Isolation Pilot Plant (WIPP) facility. This system must be capable of discriminating waste that is above the 100-nCi/g level from waste that is below this level in reasonable measurement times in an environment susceptible to varying neutron backgrounds; must be able to measure higher level waste destined for the WIPP facility with a reasonable accuracy; and finally, must be somewhat transportable. The system will consist of four slabs each having twenty 152-cm-long 3He tubes. With the four slabs placed optimally for the different types of waste containers, our calculations predict a detection efficiency of about 4.5% in the center between the four slabs. These calculations also predict that the system will be able to discriminate the LLW in 1 to 12 h, depending on the neutron background, and that the system will be able to measure WIPP crates to a 1-