Year
2016
Abstract
On March 11, 2011, the Fukushima Daiichi Nuclear Power Station lost all power sources due to the earthquake and the subsequent tsunami that gave rise to the station blackout. This resulted in the severe core damage at Units 1 to 3, involving hydrogen explosions at Units 1, 3 and 4. Despite many difficulties during recovering work, on December 16, 2011, the reactors have achieved condition of cold shutdown and have been in stable state. Decommissioning work is being carried out according to the roadmap, “Mid-and-Long-Term Roadmap towards the Decommissioning of TEPCO’s Fukushima Daiichi Nuclear Power Station Units 1 to 4”. Notable milestone of safeguards implementation at Fukushima Daiichi was reached in December 2014. All fuel assemblies in the Unit 4 spent fuel pool (SFP) have been completely removed and transferred to the common spent fuel pool and the Unit 6 pool. Approximately 80 percent of nuclear materials on site have been successfully re-verified by the end of 2014, and safeguards activities on all the nuclear materials except that in Units 1 to 3 have been returned to normal. The situation of nuclear materials in Units 1 to 3 remains unclear because it is still difficult to access each reactor building due to high radiation dose. Units 1 to 3 have commenced monitoring by outdoor surveillance cameras since mid-2014. In addition, an outdoor gamma-and-neutron monitoring system was installed in outdoor area and has been functioning since June 2015 to contribute to the objective of confirming the absence of diversion of inaccessible declared material that is a hypothetical illegitimate removal from Units 1 to 3. Currently, removal of reactor building cover is being performed at Unit 1 since July 2015, and decontamination and shielding work have been continuously carried out to lower radiation dose before installing new cover on the operating floor at Unit 3. Regarding removal of fuel debris, full submersion, partial submersion and dry method are being contemplated as applicable approaches based on the results of R&Ds in progress for each unit. Policy on fuel debris removal has to be decided in mid-2017 according to the latest roadmap. Safeguards approaches for fuel debris will be developed in consultation with IAEA and JSGO (Japan Safeguards Office).