Nuclear Material Accountancy Lessons Learned from the Three Mile Island (TMI) and Chernobyl Nuclear Power Plant (ChNPP) Accidents with Potential Application for Nuclear Material Accountancy at Fukushima Daiichi Nuclear Power Station

The Great East Japan Earthquake and Tsunami in 2011 led to the accident at the Fukushima Daiichi Nuclear Power Plant (1F) and subsequent meltdown of the reactor cores of Units 1, 2, and 3. The Japanese project on material accountancy technology development for fuel debris of Units 1-3 of 1F has been implemented under the roadmap, “Mid-and-long-Term Roadmap towards the Decommissioning of Fukushima Daiichi Nuclear Power Units 1-4” with recovery of the fuel debris starting in 2020. Japan Atomic Energy Agency (JAEA) and United States Department of Energy / National Nuclear Security Administration (DOE/NNSA) have agreed to collaborate to investigate past experience on material control at TMI-2 and ChNPP. This paper describes the material accountancy processes employed on the damaged TMI and ChNPP nuclear materials. This paper also explores how the material forms retrieved from these accidents could be placed under International Atomic Energy Agency (IAEA) safeguards, and identifies material characteristics that may be encountered at Fukushima Daiichi that would impede the application of safeguards. Study Methodology The Chernobyl Nuclear Power Plant (ChNPP) portion of this study is based on firsthand experience of U.S. laboratory experts, IAEA staff, and Chernobyl safeguards experts who evaluated new safeguards approaches that could be used at ChNPP, and literature searches of studies and reports written in the aftermath of the Chernobyl accident. The U.S. team worked directly with experts from Ukraine to devise measurement systems that could be used by Ukraine to make declarations to meet their obligations under their Comprehensive Safeguards Agreement (CSA) with the IAEA, and with experts from the IAEA to devise containment and surveillance systems that could be installed at ChNPP to confirm that all nuclear material remained in peaceful uses. The Three Mile Island (TMI) Unit 2 (TMI-2) portion of this study is also based on the first-hand experiences of the technical experts who were responsible for the removal and accountancy of nuclear material from the damaged TMI-2 reactor. While not under international safeguards obligations, U.S. domestic law required a nuclear material accountancy approach for the damaged TMI-2 fuel. This approach centered on the comparison of the calculated special nuclear material (SNM) in the core in TMI-2 at the time of the accident, to estimates of the small amount of SNM left in the core after recovery operations were completed, and measurements on the shipped materials themselves. Background information about both the ChNPP and TMI-2 accidents is not included in this paper. This paper focuses instead on specific activities related to Nuclear Material Accountancy (NMA) after the ChNPP and TMI-2 accidents. In some instances, it may