Neutron Multiplicity and Active Well Neutron Coincidence Verification Measurements Performed for March 2009 Semi-Annual DOE Inventory

The Analytical Development (AD) Section field nuclear measurement group performed six “best available technique” verification measurements to satisfy a DOE requirement instituted for the March 2009 semi-annual inventory.1 The requirement of (1) yielded the need for SRNL Research Operations Department Material Control &Accountability(MC&A) group to measure the Pu content of five items and the highly enrich uranium (HEU) content of two. No 14Q-qualified measurement equipment was available to satisfy the requirement. The AD field nuclear group has routinely performed the required Confirmatory Measurements for the semi-annual inventories for fifteen years using sodium iodide and high purity germanium (HpGe) ?-ray pulse height analysis nondestructive assay (NDA) instruments.2 With appropriate ?-ray acquisition modeling, the HpGe spectrometers can be used to perform verification-type quantitative assay for Pu- isotopics and HEU content. The AD nuclear NDA group is widely experienced with this type of measurement and reports content for these species in requested process control, MC&A booking, and holdup measurements assays Site-wide.3-6 However none of the AD HpGe ?-ray spectrometers have been 14Q-qualified, and the requirement of reference 1 specifically excluded a ?-ray PHA measurement from those it would accept for the required verification measurements. The requirement of reference 1 was a new requirement for which the Savannah River National Laboratory (SRNL)Research Operations Department (ROD) MC&A group was unprepared. The criteria for exemption from verification were7 ? isotope content below 50 grams ? intrinsically tamper indicating or TID sealed items which contain a Category IV quantity of material ? assembled components ? laboratory samples.