MEASUREMENT RESULTS FOR TWO AUTOMATED IPAN DRUM ASSAY SYSTEMS

Two automated Imaging Passive Active Neutron (IPAN) drum assay systems have been built for the Waste Receiving and Packaging (WRAP) facility in Hanford, Washington. In June 1996, the systems underwent acceptance testing at the WRAP facility. Basic IPAN design and measurement capabilities are discussed here. The systems incorporate passive and active neutron measurement techniques to assay waste drums containing various amounts of transuranic isotopes. The passive technique uses 3He detectors together with a coincidence analysis to quantify amounts of spontaneous fission isotopes such as 240Pu.The active technique is the Differential Dieaway Technique (DDT) developed at Los Alamos National Laboratory primarily by Caldwell and Kuntzl. The DDT quantifies amounts of induced fission isotopes such as 239Pu and 235U. The assay results for a waste drum are used to classify the drum as “Transuranic Waste” (“TRU”) or “Low Level Waste” (“LLW’). This allows the safest and most cost efficient storage solution for the drum. A substantial amount of test data was acquired with each system. The active measurements show an average 30 Lower Limit of Detection (LLD) of better than lnCi/g. Using Pajarito Scientific Corporation’s proprietary neutron imaging methodology, active measurement total assay errors (statistical plus systematic) of 10% or less were obtained for standard 100 second measurement times and TRU waste drum loadings of 10nCi/g. The same methodology incorporated into low level passive assay measurements (spontaneous fission neutron sources of 25 neutrons per second) resulted in an average total assay error of approximately 1270, for standard 320 second measurements.