Determination of Pyroprocessing Cathode Processor Failure Modes and Integration Into a Signature-Based Safeguards (SBS) Framework

Developing safeguards for pyroprocessing technologies faces multiple challenges. This is due to the limitations of traditional nuclear material accountancy (NMA) methods as it has difficulty in meeting the stated detection limits of the International Atomic Energy Agency (IAEA) using existing technologies. For this reason, additional safeguard approaches are being investigated by the University of New Mexico (UNM) to complement NMA in acceptably reaching these detection limits. One approach being explored is Signature Based Safeguards (SBS), which relies heavily on process monitoring where the determination of signals can be measured and continuously monitored, thus indicating potential off normal operations or corroborating false alarms that may have occurred. SBS involves a centralized data integration and interpretation (DII) module that collects multiple signatures from various different types of process measurements in order to determine with high certainty that material is being transferred within a pyroprocessing facility as designed. Previous work to determine these signatures has involved simulating the cathode output of an electrorefiner (ER) and the efficacy of resultant non-destructive assay (NDA) measurements from a high-level neutron coincidence counter. This work involved determining potential failure modes for the ER, simulating these failure modes, and determining the resulting cathode product composition. This calculated composition was used to conceptually model a metallic fuel ingot, whose radiation signatures were determined from simulated detector response. In the current paper, this work is expanded to explore potential failure modes in the processing of the cathode product following the ER and uranium consolidation steps resulting in the casting of metallic ingots. The detector response is modeled in MCNP utilizing source terms for spontaneous fission and (alpha,n) reactions developed in the code SOURCES-4C. Results show promisingly distinct signatures caused by potential failure modes in the cathode processor. This paper presents some of these potential failure modes and how the resultant signatures fit into the SBS framework. In addition, the simulated detector response results for the consolidated ingots under these various failure modes are reported, analyzed, and discussed.