Cooperation in the implementation of safeguards at Fukushima Daiichi Site

Transcription

1 Cooperation in the implementation of safeguards at Fukushima Daiichi Site Hirokazu KUMEKAWA 1), Toshimitsu ISHII 1), Masaru SHIGEYAMA 1), Ayako YAMAMOTO-OTSUJI 1), Hirozo SHIRATORI 1), Koichi SANO 1) *, Junichi NINAGAWA 1) **, Masaru NAMEKAWA 2), Shoko ISO 2), Yasunori HIRATO 2), Norihito NAKAMURA 2), Masahiro MURAJIRI 2), Keiichiro HORI 3), Katsuyoshi OYAMA 4), Takumitsu MIKAMI 4), Naoya HIRABAYASHI 4) 1) Nuclear Regulation Authority (NRA) / Japan Safeguards Office (JSGO); 2) Nuclear Material Control Center (NMCC); 3) 4) Japan Atomic Energy Agency (JAEA); Tokyo Electric Power Company (TEPCO); * Currently, Cabinet Secretariat, ** Currently, International Atomic Energy Agency (IAEA) Abstract. The accident at Fukushima Daiichi Nuclear Power Station caused by the Great East Japan Earthquake and tsunami in March 2011 had a major impact on the safeguards situation at the site. JSGO, NMCC, TEPCO and JAEA have been tackling the challenges posed by the accident jointly with the IAEA and in cooperation with the US Department of Energy (DOE). From the day of the earthquake, JSGO and the IAEA have shared information on decommissioning activities and discussed how to implement safeguards under this difficult situation. In May 2012, the Fukushima Task Force was established to develop a holistic approach to safeguards implementation measures for the site, to monitor the re-establishment of safeguards, to facilitate discussion of relevant issues, and to consider possible approaches to longer-term safeguards challenges. All the fuels in spent fuel ponds in Units 5 and 6 and Common Spent Fuel Storage facility (CSFS) have been successfully re-verified. Re-verification of fuels kept in spent fuel pond in Unit 4 is underway. A special arrangement called SNOS (Short Notice Operational Support) activities has been introduced to provide additional assurances that no declared material has been diverted at Fukushima Daiichi site. Proactive discussions have been and are being held to develop safeguards measures in keeping up with the progress of the recovery work. The damaged core material in Units 1-3 will pose extreme difficulties in longer-term. A special sub-group has been established under the task force to address the issues. Although lessons learned from past nuclear accidents resulting in damage of core material have some relevance, none of them can be directly applicable for Fukushima. Thus a foresighted and creative approach is needed. Close coordination with the IAEA and support from technically competent institutions in Japan and from abroad, such as DOE, are also essential to tackle the issues. 1. Background Japan has a long history of cooperation with the IAEA in implementing safeguards. In 1959, the Board of Governors of the IAEA approved the first agreement for the application of safeguards, covering a Japanese research reactor, JRR-3. The cooperation between the IAEA and Japan has been expanded in accordance with the development of Japanese nuclear activities. In recent years, Japan has played a leading role in making the IAEA safeguards more effective and efficient. At the time of 1

2 introduction of additional protocol, the IAEA and Japan have conducted implementation trial collaboratively. In December 1999, additional protocol concluded between the IAEA and the government of Japan firstly entered into force with a nation with nuclear power stations. Through close consultation on procedures and implementation rehearsal, integrated safeguards (IS) approach for light water reactors without MOX started in Japan in September IS approaches covering various facility types and sites have been developed one after another, and IS approaches finally started to cover all the facilities and sites in Japan in January The Great East Japan Earthquake, its impact and immediate follow-up On 11 March 2011, the Great East Japan Earthquake with a magnitude 9.0 struck broad area of northern Japan. The earthquake and subsequent tsunami which caused numerous casualties and damage on Japanese society had a grave impact on safeguards implementation. The impact on safeguards included actual physical damage on nuclear facilities, deteriorated accessibility caused by damage on infrastructure, and malfunction of safeguards equipment due to interrupted power supply caused by blackout or misalignment of surveillance cameras. Nuclear facilities which had problems in implementing safeguards due to the earthquake and tsunami are shown in FIG. 1 below. + Tokai II power station + JAEA, Nuclear Science Research Institute + JAEA, Nuclear Fuel Cycle Engineering Laboratories + Nuclear Fuel Industries Ltd. (Tokai) + Mitsubishi Nuclear Fuel + Nuclear Development Corporation + Rokkasho Reprocessing Plant + Rokkasho Enrichment Plant + Onagawa Nuclear Power Station + Global Nuclear Fuel - Japan. + Fukushima Daiichi Nuclear Power Station + Fukushima Daini Nuclear Power Station + JAEA, O-arai R&D Center + Nippon Nuclear Fuel Development CO. LTD. FIG. 1: Immediate effect of Great East Japan Earthquake on safeguards implementation Immediately after the earthquake, the JSGO started to share the available information with the IAEA to respond to this catastrophic event. Initial action of the JSGO was to support the IAEA by confirming the safety of inspectors staying in Japan and relaying messages to them, trying to contact their hotels when the IAEA headquarters could not contact them. The JSGO made every effort in cooperation with facility operators to provide the IAEA with information on accessibility to and physical damage of nuclear facilities, condition of safeguards equipment and commercial power supply every day from the day of the earthquake to 5 April Particular emphasis was placed on prompt provision of information on Fukushima Daiichi. In order to facilitate communication and understanding, the JSGO and the IAEA also had weekly meetings at Tokyo Regional Office of the IAEA to discuss on how to deal with the difficult conditions described above. 2

3 Along with the recovery of conditions, the IAEA resumed suspended inspections. By August 2011, safeguards activities at all facilities other than Fukushima Daiichi and Daini Nuclear Power Plants (NPSs) successfully returned to normal as a result of the cooperative efforts of both the IAEA and the Japanese counterparts. Locations of Fukushima Daiichi and Daini NPSs and relevant site, and major buildings of safeguards relevance are shown in FIG. 2 below. Fukushima Daiichi NPS Fukushima Daini NPS J-village FIG. 2: Locations of Fukushima Daiichi and Daini site and details of Fukushima Daiichi site Note: CSFS: Common Spent Fuel Storage facility, CCB: Cask Custody Building, TCCA: Temporary Cask Custody Area (This was built after the accident.) Regarding Fukushima Daiichi NPS, Units 1-3 were under operation and Units 4-6 were shut down for periodical safety inspections on the day of the earthquake. The emergency shut-down feature, or SCRAM, went into operation at Units 1-3 immediately after the earthquake, but the earthquake caused a total loss of off-site electricity and subsequent tsunami flooded and totally destroyed emergency diesel generators, the seawater cooling pumps, the electronic wiring system and the DC power supply for Units 1, 2 and 4, and resulting in loss of all power except for Unit 6 from diesel generator. The tsunami also destroyed buildings, equipment installations and other machinery and washed away oil tanks, vehicles, etc. After the water retreated, debris from the flooding was scattered all over the plant site, hindering movement. Manholes and ditch covers had disappeared, leaving gaping holes in the ground. In addition, damage on pathways made access to and within the site extremely difficult. Loss of electricity and aftershocks also hindered effective monitoring and communication. The loss of electricity made it very difficult to effectively cool down the reactors and monitor them. The lack of access obstructed the delivery of necessities such as alternative cooling water injection using fire trucks, the recovery of electricity supply, the line configuration of the vent and its intermittent operation. The loss of effective cooling eventually resulted in emission of hydrogen gas which caused explosions at Units 1, 3 and 4 and damage to suppression chamber at Unit 2. Status of each unit at the time of the earthquake and immediately after the accident, and nuclear material at each unit just after the accident is shown in Table 1 and 2 below, respectively. 3

4 Table 1: Status of each unit of Fukushima Daiichi NPS at the time of the Great East Japan Earthquake and immediately after the subsequent accident Status on 11 March Unit Status immediately after the accident Operating Core fuel may have melted / Reactor building was damaged. /Very high radiation dose 2 Operating Core fuel may have melted / Very high radiation dose 3 Operating Core fuel may have melted / Reactor building was damaged. /Very high radiation dose CSFS CCB Shutdown for periodical safety inspection Shutdown for periodical safety inspection Shutdown for periodical safety inspection Operating Operating Reactor building was damaged. / High radiation dose / No fuel was in the core. All fuel was in the spent fuel pond. Accessible to Reactor building / Loss of partial power supply in Reactor building (No power supply for IAEA cameras and partial lights) / Crane and Fuel handling machine unusable / Fuels in Spent fuel pond were not confirmed. Accessible to Reactor building / Loss of partial power supply in Reactor building (No power supply for IAEA cameras and partial lights) / Crane and Fuel handling machine unusable / Fuels in Spent fuel pond were not confirmed. Accessible to the building / Loss of partial power supply in building (No power supply for IAEA cameras and partial lights) / Crane and Fuel handling machine unusable / Spent fuels in Spent fuel pond were not confirmed. Not accessible due to scattered rubbles / Some seals were partially damaged. (especially immobilized COBRA) Table 2: Item list of Fukushima Daiichi at the time of the accident Unit Location Core Spent Fuel Pond (melted fuel debris) 100 (FF), 292 (SF) (melted fuel debris) 28 (FF), 587 (SF) (melted fuel debris) 52 (FF), 514 (SF) 4 None 204 (FF), 1331 (SF) (FF), 428 (IF) 48 (FF), 946 (SF) (FF), 580 (IF) 64 (FF), 876 (SF) CSFS N/A 6,375 (SF) CCB N/A 408 (SF) in 9 casks Note: FF: fresh fuel, SF: spent fuel, IF: irradiated fuel 4

5 TEPCO continued every effort to control crippled reactors and eventually achieved cold shut down in December The buildings of Units 1, 3 and 4 were damaged severely and rubbles contaminated with radioactive materials were dispersed. Therefore, the radiation dose rate at Fukushima Daiichi site, especially the area around Units 1-4 was high. The first inspection after the earthquake was performed from 5 to 7 October Inspectors were able to access Units 5, 6 and the CSFS and the CCB in the inspection. Before going into Fukushima Daiichi site, each inspector equipped with protective suits, plastic gloves, a cap and a cotton mask at the J-village, located approximately 20 km south from the Daiichi site. At the Fukushima Daiichi site, they equipped with full face masks. Result of the inspection is shown in Table 3 below. After the first inspection, inspections have been conducted at Units 5 and 6 and the CSFS with an interval of 3 month. Table 3: Result of the first inspection after the accident Unit Core Declared Nuclear Material 1-3 Not accessible. Not accessible. 4 No fuel assemblies Not accessible. 5 6 CSFS CCB C/S was failed. Lid of pressure vessel was closed, but seal was not attached at the top of the core yet because the earthquake happened before the end of periodical safety inspection. Seal was attached. It was confirmed later that containment and surveillance was maintained through the accident. N/A N/A Spent Fuel Pond C/S was failed. Existing ALIS surveillance cameras were not functioning properly due to blackout. New ALIP surveillance cameras were installed. C/S was failed. Details were the same as above. C/S was failed. Details were the same as above. At least one seal for each cask was maintained. Validity of the seals was confirmed later. With regard to Fukushima Daini NPS, Units 1-4 were under operation on the day of the earthquake. SCRAM went into operation at Units 1-4 immediately after the earthquake. The earthquake didn t cause a total loss of off-site electricity but subsequent tsunami flooded and partially destroyed emergency diesel generators, the seawater cooling pumps, the electronic wiring system and the DC power supply for Units 1-4, and resulting in keep of power. The tsunami also destroyed buildings, equipment installations and other machinery. The first inspection after the earthquake was carried out on 31 May Inspectors were able to access all buildings of Units 1-4. They confirmed all the ALIS surveillance cameras installed at the site were operating normally and installed new ALIP surveillance cameras as a backup. Seals attached to the top of the core of each reactor were checked and replaced as normal. However, they 5

6 could not verify the fuel in the pond during the inspection due to water turbidity caused by the failure of the water cleanup system and damage on fuel handling machines. Since then, inspections have been carried out with an interval of 3 month. Gradual resolution of the problems made it possible for the inspectors to start verification of the fuel in the spent fuel ponds at Units 1, 2 and 4 in the first half of Fukushima Task Force While safeguards activities at all facilities except Fukushima Daiichi and Daini NPSs returned to normal within 2011, Fukushima Daiichi and Daini remained as issues of safeguards implementation. In order to address the issues, Mr. Herman Nackaerts, then Deputy Director General and Head of the Department of Safeguards of the IAEA, and Mr. Kanji Fujiki, then Deputy Minister of Education, Culture, Sports, Science and Technology (MEXT) of Japan, agreed to establish Fukushima Task Force at the Joint Committee Meeting, which is composed of the representatives of the government of Japan and the IAEA, held in March The task force is participated by relevant staff of the Department of Safeguards of the IAEA, JSGO, NMCC, JAEA and TEPCO. The objective of the task force is threefold as follows: Firstly, to develop a holistic approach to safeguards implementation measures being considered for the Fukushima Daiichi site; Secondly, to monitor the recovery of safeguards at the Fukushima Daiichi and Daini nuclear power plants, and to facilitate discussion of issues which may be of relevance to this objective; Thirdly, to consider possible approaches to longer-term safeguards challenges arising from the March 2011 accident. On 31 May 2012, the first task force meeting was held in Vienna. Since then, following four task force meetings have been held until September In addition to these meetings, Fukushima Daiichi site was visited by the members of the task force in October 2012, Mr. Nackaerts and Mr. Marzo, the director of SGOA, in January 2013, Mr. Varjoranta, the Deputy Director General and head of the Department of Safeguards, in April Subgroups have also been established to discuss specific issues under the task force. Through these meetings and site visits in addition to regular and ad-hoc information provision including monthly information on Road Map for safeguards recovery, information about safeguards status and other information which has relevance with safeguards activities, updated status of and planned activities at the site is shared with the IAEA. At CSFS, damaged fuel handling machine was restored and re-verification of all 6,375 fuel assemblies there was successfully completed in July Due to insufficient capacity of CSFS to receive spent fuel assemblies from the spent fuel ponds of Units 1-4 and the damage of CCB, Temporary Cask Custody Area (TCCA) was constructed to accommodate spent fuel assemblies from CSFS and CCB. The operation of TCCA started in April Spent fuel in CCB was verified at CSFS and transferred to TCCA. The operation of TCCA and recovery work at Unit 4 enabled the IAEA inspector to re-verify fuel assemblies in the spent fuel pond of Unit 4 after their transfer to CSFS. Such re-verification started in November With 6

7 regard to Fukushima Daini, it was agreed at the task force meeting in November 2012 to complete following up the status of the NPS under the task force as the safeguards activity for the NPS had returned to normal. Another important function of the task force meetings is to discuss safeguards approach and practical arrangements for safeguards implementation at the sites in line with the recovery work there. Regarding Fukushima Daiichi, new measures have been discussed and agreed for safeguards implementation. After discussion on procedures and trial implementation, SNOS activities have been introduced for the implementation of safeguards at Fukushima Daiichi site, in addition to inspections, design information verifications and complementary accesses. SNOS activity is a safeguards measure that is agreed between the IAEA and the government of Japan beyond the legal scope of safeguards agreement and additional protocol. SNOS activity enables the IAEA inspectors to confirm the consistency of the operational activities declared by the facility operator in relation to the recovery work at the site and to provide additional assurances that no declared material has been diverted. By the end of September 2014, SNOS activities have been conducted already five times since the initial activity in February At the operation floor of Unit 3, removal of rubbles and decontamination work is ongoing. Although radiation dose rate is still high at Units 1-3, safeguards measures to monitor the decommissioning activities around Units 1-3 have been discussed at the task force meetings. As the result of the discussion, independent radiation measurement at the operating floor of Unit 3 and installation of XCAMs to monitor Units 1-3 has been implemented. The result of the independent measurement corresponds to the declaration from the operator. 4. Recent status of the recovery of safeguards implementation and future actions All the core fuel in Unit 6, spent fuel in CCB, the fresh and spent fuel stored at spent fuel ponds in Units 5-6, CSFS have been successfully re-verified and are currently under C/S. Since November 2013, operation to transfer the fresh and spent fuel stored at Unit 4 to CSFS have been carried out and re-verification of those fuel assemblies have been conducted at CSFS. 82% of fuel assemblies stored at spent fuel pond of Unit 4 have been re-verified and the re-verification is expected to be completed within By the end of 2014, re-verification of core fuel of Unit 5 is also anticipated and four out of the original seven anomalies are expected to be resolved. While radiation dose rate at Units 1-3 is still high and three anomalies remain, appropriate monitoring should be continued. After safety operation is established, fuel assemblies stored at spent fuel ponds of Units 1-3 are expected to be transferred to and re-verified at CSFS. Summary of the current and anticipated status is shown in Table 4 below. The safeguards approach for damaged core fuel in Units 1-3 should be based on the technical condition of the nuclear material in the cores and on plans for handling the material. In this regard, DOE s National Nuclear Security Administration (DOE/NNSA), MEXT and JAEA agreed to establish long-term cooperation on safeguards issues on Fukushima Daiichi NPS. Base on the agreement, studies have been conducted on lessons learned from past accidents including Three Mile Island and Chernobyl and on potential technologies to be applied for nuclear material accountancy of damaged core fuel. 7

8 Table 4: Current and anticipated safeguards status (as of 30 September 2014) Unit Core Declared Nuclear Material Spent Fuel Pond (SFP) 1-3 Not accessible. Safeguards approach should be developed in due time. Not accessible. Spent fuel is expected to be re-verified after transferred to CSFS. 4 No fuel assemblies 1,256 out of 1,535 fuel assemblies stored in the SFP have been re-verified after their transfer to CSFS. Completion of the re-verification of all the fuel assemblies is expected in CSFS CCB Core opening is under preparation. Re-verification of the core fuel is anticipated in late All the fuel assemblies have been re-verified and are under C/S. N/A N/A All the fuel assemblies have been re-verified and are under C/S. All the fuel assemblies have been re-verified and are under C/S. All the fuel assemblies have been re-verified and are under C/S. All the fuel assemblies have been transferred to TCCA. TCCA N/A All the fuel assemblies are under Dual C/S. 5. Conclusion Implementation of safeguards at Fukushima Daiichi is an unprecedented challenge for the safeguards community. Close cooperation among the IAEA, the JSGO and other relevant organizations in Japan have enabled the successful and progressive recovery of safeguards implementation at the site. However, high radiation dose rate at Units 1-3 and complicated recovery operation makes the remaining issue challenging. To tackle the remaining issue, the JSGO will continue to provide sufficient information to the IAEA in collaboration with the relevant parties in Japan. In addition, considering the nature of the challenge, creative approach to establish robust safeguards measures should be pursued in close cooperation between the IAEA and the Japanese counterparts and with the technical support from the US DOE. 6. References [1] David Fischer, Nuclear Safeguards: The first Steps, IAEA Bulletin 49/1, September [2] Masashi Hattori, et al, Safeguards Activities and Plan for Strengthening Safeguards and Nuclear Security After the Great East Japan Earthquake, INMM, July [3] The National Diet of Japan, The official report of The Fukushima Nuclear Accident Independent Investigation Commission. Executive summary, [4] Tokyo Electronic Power Company, Inc., Fukushima Nuclear Accident Analysis Report <Summary>, 20 June