NRA s Regulatory Perspectives on Decommissioning of TEPCO Fukushima Daiichi Nuclear Power Station

Transcription

1 NRA s Regulatory Perspectives on Decommissioning of TEPCO Fukushima Daiichi Nuclear Power Station September 18, 2017 Yutaka HARA Nuclear Regulation Authority (NRA), Japan

2 1 Contents Approach in NRA s Regulation of Fukushima Daiichi Topics -Contaminated water (Stagnant) -Slurry -Sludge -Processed water (Stored) -Debris removal Conclusion

3 2 Approach in NRA s Regulation of Fukushima Daiichi (1/2) Reducing risks rapidly, with minimizing negative effects to the public and environment in the region and radiation exposure to employees

4 3 Approach in NRA s Regulation of Fukushima Daiichi (2/2) Risk oriented ( Prioritize and reduce risks: imminent risk, First) Mid-term Risk Reduction Map by NRA (Latest: July 2017) ( Fact based (Obtain vital information inside R/Bs, PCVs, T/Bs etc. ) Safety, Timely (Do now whatever can be done) Flexibility ( Be prepared for unexpected, maximize use of available resources, information and knowledge)

5 Contaminated water (Stagnant) (1/2) Regulatory Perspectives Reduction of leakage risk of contaminated water accumulated in R/Bs, T/Bs, etc. Inventory: ~ Bq As of 2011 Upper permeable layer Desalination and removal of cesium Reactor building Large amount of highly radioactive water is stagnated in R/Bs and T/Bs Sub-drain Turbine building trench Figures by TEPCO Figures by TEPCO, edited by NRA

6 inventory of contaminated water The amount of contaminated water is decreasing under control: Unit 1 T/B floor was dried out in August 2017 The work on T/Bs of Units 2&3 is in progress Contaminated water (Stagnant) (2/2) (Bq) App (August 2017) Bq Present Inventory: ~ Bq Inventory of contaminated water in the buildings including condensers and trenches Inventory of contaminated water in condensers App Bq as of Dec Trend of inventory of contaminated water in R/Bs and T/Bs Source: TEPCO, Edited by NRA 5

7 Slurry Regulatory Perspectives Reducing risks of highly radioactive slurry from ALPS in HICs. Storage of HICs containing slurry Coastline Contents in slurry (Inventory of 90 Sr) FeO(OH) H 2 O (App Bq) CaCO 3, Mg(OH) 2 (App Bq) Inventory: ~ Bq ALPS:Advanced Liquid Processing System HIC: High Integrity Container Storage amount App. 1000m 3 (366 HICs) App. 4,900m 3 (1,888 HICs) (July 2017) Remaining Issues TEPCO has been planning stabilization (dehydration etc. ) and immobilization of slurry Figures by TEPCO, edited by NRA Stabilization and immobilization of slurry in HICs need to be started as soon as possible 6

8 Sludge Regulatory Perspectives Preventing release of highly radioactive sludge from AREVA system by earthquake / tsunami Coastline Inventory Bq 3 Storage amount 597m 3 Storage for sludge from AREVA system Remaining Issues <Present> 10m above sea level <Future> Higher place on the site Removing and transporting sludge generated from AREVA system (in progress) Then, stabilization Sludge Schematic diagram of granulated and solidified storage Figures by TEPCO, Edited by NRA Basement 7

9 Processed water (Stored) (1/2) Google 8

10 Processed water (Stored) (2/2) Treated water containing tritium has been increasing, however capacity of tanks is limited Harmful rumors could be a concern in the region Inventory: ~ 10 7~12 Bq 0.2% 19.5% Treated Water Total App. 1,000,000m 3 (August, 2017) 80.3% App. 800,000m 3 Treated Int. B Int. A ALPS treated water Cs and Sr reduced water Cs reduced water Remaining Issues Source: TEPCO, Edited by NRA Discharging the treated water containing tritium to the sea under the conditions which comply with the regulatory requirements, etc. 9

11 Regulatory Perspectives Debris removal Rapid fuel debris removal in a safe manner is important Fact findings/analysis of Fukushima Daiichi accident is also important Evaluation of structural integrities of RPVs and PCVs RPVs and PCVs were damaged (Unidentified leak paths, aging effects, etc. ) Collecting more data and information inside RPVs, PCVs and R/Bs Location, physical/chemical forms and other properties of fuel debris Integrities of buildings, piping, etc. Dose distribution, etc. Leaking path from a drain pipe Source: TEPCO, Edited by NRA Remaining Issues Leaking path at Unit 1( November 2013) Obtaining information on and inside RPVs, PCVs and R/Bs, as a base of planning and safety evaluation of fuel debris retrieval and for analysis of the accident. 10

12 11 Conclusion TEPCO Fukushima Daiichi site has shifted from Emergency Response Stage to Planned Action Stage. Some measures, however, are delayed, and still so many tasks are to be accomplished regarding contaminated water, radioactive waste and so on. Field surveys inside RPVs, PCVs and R/Bs are vitally important for TEPCO and NRA to obtain information for planning and safety evaluation of fuel debris retrieval and for analysis of the accident.

13 Thank you for your attention 12

14 Appendix 13

15 Governmental framework for decommissioning of Fukushima Daiichi NPS Nuclear Emergency Response Headquarters Chair: Prime Minister Vice-Chair: Cabinet Secretariat, Minister of Economy, Trade and Industry, Minister of the Environment, Chairman of NRA Member: Ministers Participation Team for Decommissioning and Contaminated Water Technical Advice Countermeasures Head: Minister of Economy, Trade and Industry Risk identification Progress management Financial support Regulation TEPCO NRA 115

16 Mid-term Risk Reduction Map In order to communicate existing mid-term risks at TEPCO Fukushima Daiichi NPS to the public, the NRA published Midterm Risk Reduction Map in February 2015 (Latest updated in July 12, 2017) To address risk concerns plainly by presenting key priorities for safety identified by the NRA among the various measures taken by TEPCO for decommissioning. To clearly distinguish completed measures from ongoing and planned ones. Website of Mid-term Risk Reduction Map (English) 15

17 (Provisional Translation) Issue Objective (year) Contaminated water Avoiding leakage of contaminated water from tanks etc. Removing highradioactive contaminated water from the sea-side pipe trenches (Units 2-4) (June. 2015; Unit 2, July. 2015; Unit 3, Dec. 2015; Unit4)) Completing removal of tanks lacking concrete foundations and/or dikes (Dec. 2014;H1 Area) Removing highradioactive contaminated water from boltjoint tanks (May.2015) Measures for Mid-term Risk Reduction at TEPCO s Fukushima Daiichi NPS (as of July 2017) Treating highradioactive contaminated water in tanks (May. 2015) Preventing the outflow of contaminated groundwater into the sea by completing the sea-side underground impermeable wall including sub-drain control systems (Oct. 2015) Managing the increase of the total capacity of water in tanks by restraining the inflow of groundwater into Reactor Buildings(R/Bs) and Turbine Buildings(T/Bs) Removing (treated) contaminated water from bolt-joint tanks Treating contaminated water in R/Bs and T/Bs. To reduce the amount of radioactive material to less than half. Completing treatment of contaminated water in R/Bs and T/Bs. Preventing the outflow of contaminated water in R/Bs and T/Bs. Accurately controlling the levels of groundwater and contaminated water in R/Bs and T/Bs (Oct. 2015) Reducing the volume of contaminated water in tanks by discharging the water after necessary treatment to the sea in accordance with the regulatory requirements, etc. Radioactive waste Preventing scattering and leakage of radioactive waste during decommissioning processes Starting operation of incineration plants for miscellaneous radioactive waste e.g. protective clothing (Mar. 2016) Transferring3 to the stable management of secondary waste from treatment of contaminated water e.g. sledges in the High Integrity Container(HIC)s, etc. Starting operation of the 9 th storage facility for radioactive waste Starting operation of Radioactive Material Analysis and Research Facility-1 Stopping of outside storage (used protective clothing) Starting operation of temporary storage facilities for contaminated soil Starting operation of large storage plants Starting operation of incineration plants for felled trees, flammables in rubble, etc. Starting operation of volume reduction plants (metal, concrete) Spent fuel Removing fuel from Spent Fuel Pools (SFPs) Completing fuel removal operation at Unit 4 SFP (Dec. 2014) Completing construction of Unit 3 R/B cover and completing fuel removal facility Completing fuel removal operation at Unit 3 SFP Completing construction of Unit 1 R/B cover and completing fuel removal facility Completing construction of Unit 2 R/B cover and completing fuel removal facility Earthquake / Tsunami Site and environmental protection from Earthquake / Tsunami Construction of temporary seawall (June 2011) Preventing the outflow of contaminated water anticipating the recurrence of the 2011 Tsunami (max 15.5m) Blocking the openings (Sep.2013; Common Pool, Oct.2014; Unit 1 T/B, Unit 2 T/B, HTI) Preventing the outflow of contaminated water anticipating the recurrence of the 2011 Tsunami (max 15.5m) Blocking the openings (Unit 3 T/B, Process main building ( planned)) Scientifically providing the greater earthquake/tsuna mi model (900 gal, 26.3m),and establishing the basic protection plan that corresponds to this model (Dec. 2015) Implementing the site protection measures for Mega-Float (Tanker) following the established plan Dismantling of the upper part of stack for Units 1 and 2 Stabilizing sludge generated from decontamination device Effective dose at the site boundary (estimated value) Managing off-site effective dose during decommissioning processes Managing the additional effective dose to 2mSv/year* or less by continuous radiation monitoring and by treating highradioactive contaminated water etc. (Mar. 2015) *Estimated value Managing the additional effective dose to 1mSv/year* or less (Mar. 2016) *Estimated value Preventing scattering of dusts Preventing scattering of radioactive dusts during decommissioning processes Implementing the countermeasures against scattering of dusts, in light of the scattering incident from Unit 3 (optimization of dispersion of scattering prevention chemicals and installing more dust monitors ) (2013) Implementing and monitoring of enhanced countermeasures against scattering of dusts Completing rubble removal operation at Unit 3 SFP (Dec.2016) Implementing and monitoring of enhanced countermeasures against scattering of dusts Dismantling of the covering of Unit 2 Completing rubble removal operation at Unit 1 operating rooms and SFP [Note] Completed measures: Measures in progress or in preparation: Measures (Timing TBD): Work environment Enabling a sustainable work environment for decommissioning Managing a work environment not requiring full-face mask respirators excluding the vicinity of R/Bs etc. (May. 2015) Completing on-site decontamina tion excluding the vicinity of R/Bs etc. (Sep. 2016) Building the foodservice center (Mar. 2015) Building the large resting facility (May. 2015) 12 July, 2017 Examining the inside of the facilities Understandin g the internal situation of the damaged facilities Examining the process of accumulation of contaminated water in R/Bs, etc. Characterizing nuclides in water passing through the reactors Analyzing the contaminated water of the inside of R/Bs, etc. Directly observing inside of Primary Containment Vessels(PCVs) and Reactor Pressure Vessels(RPVs)

18 Removal of stagnant water in trenches Accomplished removal of highly radioactive contaminated water from the seaside pipe trenches (Units 2&3) (July. 2015) T/B (Unit3) T/B (Unit2) Seaside pipe trench(unit2) Seaside pipe trench(unit3) Highly contaminated stagnant water Unit 2 Unit 3 Concentration(Cs134+Cs137) ~10 9 Bq/L ~10 8 Bq/L (As of November 2013) Source: TEPCO, Edited by NRA 17

19 Pumping up groundwater from Sub-drain pits Pumping up groundwater from Sub-drain pits is the most essential measure The inflow of groundwater to R/Bs and T/Bs has been under control The water level inside the building shall be lower than the ambient water ( Pumping up app. 500m /day[july]) 3 Water level differenc e 6Paved with asphalt Rain Groundwater level Upper permeable layer Low-Permeable layer 2Expansion of tank 1Treat by ALPS 3Groundwater bypass Water pumping Pumping well 4Sub-drain Water pumping Desalination through removal of cesium Reactor building Turbine building 4Sub-drain 8Ground improvement Water pumping by sodium silicate 2trench Water pumpin g Sea Level Well point Groundwater drain Source: TEPCO, Edited by the NRA Source: TEPCO, Edited by the NRA Figures by TEPCO 5Land-side impermeable all 5Land-side impermeable all 9Sea-side impermeable wall

20 Spent fuel Regulatory Perspectives Removing risk of spent fuel pools Storage status of spent fuel pool Removal of spent fuel from Unit 4 was completed in 2014 * Present phase Step of installing Unit 3 fuel removal cover etc. Figures by TEPCO, edited by the NRA Remaining Issues Removing spent fuel from Unit 3 steadily (in progress) Removal method of spent fuel from Unit 2 and Unit 1 (under discussion) 19

21 Regulatory Perspectives * Effective dose at site boundary Managing off-site effective dose during decommissioning processes Dose due to solid waste etc. Dose due to sprinkling water Dose due to liquid waste Dose due to gas waste Keeping low level and stable after March 2015 Trend of the site boundary effective dose (The values exclude the background inside and outside of the site) Figures by by TEPCO, edited by the NRA 20