An External Remote Monitoring System for Safeguarding Spent Nuclear Fuel in Interim Dry Cask Storage

Abstract

Until a solution for long-term storage of spent nuclear fuel (SNF) is implemented, interim dry cask storage will be used to store SNF from nuclear power reactors. A dry cask housing 32 SNF assemblies will contain several significant quantities of plutonium, so the cask must be subject to rigorous safeguards monitoring. The current International Atomic Energy Agency (IAEA) safeguards approach for SNF in dry cask storage is limited to containment and surveillance to maintain a continuity of knowledge. An external remote monitoring system (RMS) is proposed to advance the dry cask safeguards regime. A successful RMS will reduce the inspection burden on both safeguarded facilities and the IAEA and increase the timeliness of results. The objectives of this study were to design and prototype an external RMS, to compare dry cask measurements conducted with the prototype device to simulation results, and to evaluate the ability of the external RMS to detect single fuel assembly diversions from a loaded dry cask. In this study, an external RMS was designed, and a prototype device was constructed of 3-D printed plastic parts and basic hardware. The prototype was tested in a small-scale, laboratory setting and then utilized to conduct field measurements on two dry casks loaded with SNF from a civilian nuclear power reactor at a commercial independent spent fuel storage installation. Results from the field measurements were used to perform neutron transport simulations of SNF assembly diversions from several dry cask SNF loading patterns. The study concluded that the external RMS can achieve the target non-detection probability of 10% within an acceptable measurement time even for very difficult diversion scenarios, for restrictive values of false alarm probability, and with many conservative assumptions made. The external RMS developed in this study is a viable tool for safeguards monitoring of SNF in dry cask storage.