Evolution of Nuclear Material Accountancy and Implications for State Systems of Accounting for and Control of Nuclear Material

The Nuclear Materials Management and Safeguards System (NMMSS) is the United States government’s national system to track the movement, use, inventory, and location of all accountable U.S. nuclear materials including plutonium and highly enriched uranium (HEU), domestically and internationally. It is the most comprehensive transaction-based information system concerning U.S. nuclear materials, including materials involved in worldwide commerce. The origin of present-day NMMSS can be traced back to the 1940s, when the U.S. nuclear fuel cycle was, above all, a national security enterprise.During the ensuing decades, major developments and evolving national priorities have influenced changes to nuclear materials reporting. The reporting requirements over time have not remained static but instead continue to evolve as a result of changes in both the domestic and international geopolitical environment and resultant changes in reporting requirements.The focus of this paper is to explore the international reporting aspect of NMMSS and summarize the best practices resulting from this evolutionary process. The best practices have been distilled from more than 50 years of NMMSS operations with the hope that such information may prove to be useful in future similar endeavors. It offers a unique vantage point that can only be gained through hands-on implementation of the myriad reporting requirements.