Strengthened Nuclear Safeguards: A Statistical View in the Context of Combining Process Monitoring and Nuclear Material Accounting Data

“Integrated/strengthened safeguards” is the International AtomicEnergy Agency (IAEA) concept that effective safeguards must bemaintained at monitored nuclear facilities, the mission of monitoringfor undeclared facilities must be added, and the safeguardsbudget must remain approximately constant.In traditional safeguards, periodic nuclear materialsaccounting (NMA) measurements confirm the presence ofspecial nuclear material (SNM) in accountability units towithin relatively small measurement error. Process monitoring(PM) is used to confirm the absence of undeclared flows thatcould divert SNM for illicit use. Despite occasional attemptsto quantify the diversion detection capability of PM, nearly allquantified statements regarding safeguards effectiveness involveNMA, with PM used as a qualitative added measure. To assessthe extent to which PM can provide quantitative assessmentin effectiveness evaluation is one of ten recognized technicalchallenges (discussed during the IAEA’s “Consultancy Meetingon Proliferation Resistance Aspects of Process Management andProcess Monitoring/Operating Data” held in Vienna, September28-30, 2011) in the anticipated increased use of PM data.Effective resource allocation requires effective safeguardssystem evaluation. This paper reviews safeguards system evaluationmethods based on statistical and decision theory, proposes a newevaluation method that quantifies an overall system consistingof both PM and NMA via detection probabilities for specifiedscenarios that are prioritized using diversion path analysis, andgives three examples at a hypothetical aqueous reprocessing facility.