Year
2024
Abstract
| For over 35 years, the U.S.-Japan bilateral cooperation activities on international nuclear safeguards have been essential to the development of current international and domestic safeguards techniques, instrumentation, and expertise. Through this cooperation, U.S., Japanese, and international safeguards experts developed and refined many of the International Atomic Energy Agency (IAEA) standard Non-Destructive Assay (NDA) and Destructive Analysis (DA) techniques.The U.S. Department of Energy/National Nuclear Security Administration’s International Nuclear Safeguards Engagement Program (INSEP) currently supports a project between Los Alamos National Laboratory (LANL) and Japan Atomic Energy Agency (JAEA). This includes addressing assay-to-declared differences that have been higher than expected for Epithermal Neutron Multiplicity Counter (ENMC) verification measurements of high-alpha items at the Japan Atomic Energy Agency (JAEA) Mixed OXide (MOX) fuel fabrication facility. These items originate from recent decommissioning efforts and are in the range of few to hundreds of grams Pu in both clean MOX and with low Z contamination yielding high α values (α up to ~40). Performance for these distinct items motivated the present study exploring slight modifications to the standard multiplicity analysis within the INCC software framework. This includes the Dual Energy Point Model to account for different efficiency of neutrons from (α,n) relative to fission, and backing out the optimal detector parameters (i.e., efficiency, Doubles and Triples gate fractions) based on the fact these items are very different than the reference 252Cf sources and small MOX sources used in initial detector characterization and differ from MOX materials conventionally verified in ENMC. |