PNNL

Abstract

In recent years, the International Atomic Energy Agency (IAEA) has pursued innovative techniques and an integrated suite of safeguards measures to address the verification challenges posed by the front end of the nuclear fuel cycle. Among the unattended instruments currently being explored by the IAEA is an Unattended Cylinder Verification Station (UCVS), which could provide automated, independent verification of the declared relative enrichment, 235U mass, total uranium mass, and identification for all declared uranium hexafluoride (UF6) cylinders in a facility (e.g., uranium enrichment plants and fuel fabrication plants). Under the auspices of the United States and European Commission Support Programs to the IAEA, a project was undertaken to assess the technical and practical viability of the UCVS concept. Phase I of the UCVS viability study was centered on a long-term field trial of a prototype UCVS system at the Westinghouse Fuel Fabrication Facility in South Carolina, USA. A key outcome of the study was a quantitative performance evaluation of two nondestructive assay (NDA) methods being considered for inclusion in a UCVS: Hybrid Enrichment Verification Array (HEVA), and Passive Neutron Enrichment Meter (PNEM). This paper will provide context for the UCVS and potential implementation concepts, a description of the UCVS prototype design, and an overview of the long-term field trial at a fuel fabrication facility. Selected field-trial results and interpretation are presented, including the performance of PNEM and HEVA for the verification of declared enrichment and 235U mass in over 200 “typical” Type 30B cylinders. Example results from a modeling study provide a preliminary assessment of sensitivity to material-substitution scenarios, for the as-fielded NDA methods.