Year
2000
Abstract
Self-shielding effects from large particles present difficulties for active neutron and gamma systems. If Pu “lumps” are present, these systems can only “see” a fraction of the true mass, causing an underestimate of the Pu. BNFL Instruments has developed a new algorithm that allows the large particle presence to be recognized and quantified. This algorithm has been incorporated into BNFL Instruments’ Mobile Assay System (MAS) and utilizes the active portion of the imaging passive/active neutron (IPANTM) measurement and gamma energy analysis (GEA). In October 1998, BNFL Instruments’ IPANTM/GEA MAS completed Cycle 5A of the Performance Demonstration Program (PDP) for the Waste Isolation Pilot Plant. As part of Cycle 5, large particle PDP standards were created to test system capabilities to properly quantify Pu that may exist in this form throughout the DOE complex. The BNFL Instruments lump correction algorithm was tested for the first time during this cycle. The method produced results consistent with the activity loading of the drum of 0.321 Ci passing both the precision and accuracy requirements. The correction factor for the PDP drum, produced by this new method, indicated that the true mass was four times greater than the active neutron measurement alone indicated.