The 5th International Forum on the Decommissioning of the Fukushima Daiichi Nuclear Power Station Issues at the TEPCO’s Fukushima Daiichi NPS from the Nuclear Regulator’s Perspective 1st, November, 2021 Shuichi Kaneko Nuclear Regulation Authority, Japan
1. Major Risk Issues
Countermeasures for Risks which would have an effect on the human and the environment OTreatment of Stagnant Water in Reactor Buildings etc. ORemoval and Stabilization of Zeolite Sandbags in basement floors of Process Main Building etc. O Transfer and Stabilization of Sludge from Decontamination Equipment OMeasures to prevent structures from collapsing or being damaged by earthquake, tsunami, etc. • Removal of fuels from SFPs of Unit 1 and 2 1
Location of radioactive materials (Mainly Cs-137 ) (spent fuels not included) (unit ;PBq)  * : listed up in the ascending order of stability •   Amount of Cs-137 released to the environment is estimated, referring to ГAdditional report of the Japanese government to IAEA—about the TEPCO Fukushima Daiichi Nuclear Power Station accident — (the second report) J and considering reduction •  This material shows the location of Cs−137 except for spent fuels. However, besides Cs−137, 36 PBq of Sr−90 (in process main building and concentrated liquid waste tank area) , 0.69 PBq of H−3 (in tank area) exist. •  Since fraction is rounded up or down, sum of ① ～ ⑥ doesn't match the total amount. 6)Cs-137 released to the environment Concentrated liquid waste ALPS treated water 2
• In Dec. 2018, TEPCO investigated dose rate of the basement floors of PMB and HTI buildings, and detected high dose rate at the bottom then: 2,600mSv/h in PMB, 800mSv/h in HTI. • The cause of high dose rate was sandbags containing zeolite installed right after the accident to decrease concentration of nuclides in contaminated  water temporarily stored in PMB and HTI. The highest measured surface dose rate of sandbag was approx. 3000mSv/h in PMB and  approx. 4000mSv/h in HTI • In PMB and HTI stagnant water shields radiation from the sandbags; therefore, to remove stagnant water alternative shields are required with the sandbags exposed to the air. • Able to collect at once Disadvantage • Need prepare shielded container and place to store • Equipment to collect sandbags become high dose Advantage • Able to secure storage space for the  time being Disadvantage • Need to collect the container later • Able to implement early Disadvantage • Difficult to collect later •Sandbags exist in wide range and difficult to fill all the area 5
Cross-sectional view of PMB around Pit D
【Sludge】
Precipitate adsorbed nuclides such as Cs-137 in adsorbent solution. ・Main components  : Barium sulfate(66%) Ferrocyanides · Major nuclide : 90Sr  (Approx. 3×108Bq/cm³) · Water content : Approx. 80% · Amount of sludge : 37m³ Source:TEPCO,Edited by NRA
o At ALPS, contaminated water is treated with pretreatment facility and ALPS equipment in sequence, and 62 radioactive substances are removed (except for tritium). reinforcement body)
※ 2 : Amount as of 28 May, 2018. The recent number of HICs is 3,632 in total as of 5 Nov. 2020 which store slurry and spent adsorbents. Source:TEPCO,Edited by NRA 7
Basing on the assumption that Cs-137 concentrates under-surface of the upper shield- plug, analytical calculation was made. Cause of High-Dose Rate at Operating Floor of  Unit 1-3 Calculated Amount of Cs-137 beneath the Shield Plug Image of Unit 1 Shield Plug (from west-side) ※Analytical calculation ; NRAJ, “Investigation and analysis of the TEPCO's Fukushima Daiichi NPS Accidents”, Appendix 7-1, p.185, (2021.3.5) https://www.nsr.go.jp/data/000345595.pdf
●  NRA’s Review for TEPCO Fukushima Daiichi NPS Viewpoints of the NRA’s review for ALPS treated water discharge equipment (Tentative)
Review based on the Reactor Regulation Act
The NRA will review the TEPCO’s implementation plan whether it conforms to the regulatory requirements* including the following (* “Items required for Measures which should be taken at Tokyo Electric Power Co., Inc.’s Fukushima Daiichi Nuclear Power Station in line with the Designation as the Specified Nuclear Facility" ): ▷ II.9 Treatment, storage, and management of radioactive liquid waste ▷  II.11 Radiation protection, etc. in the area surrounding the site by restricting release of radioactive materials, etc. ➤ II.14 Design considerations Confirmation along with the government basic policy The NRA will confirm whether the TEPCO’s implementation plan is in line with the government basic policy.
Waste Generations at 1F SiteんStagnant Water A Water from Underground A Rain Water A Secondary Waste from Water Treatment A Contaminated Rubbles A Fuel Debris and Reactor Structures > Identify human and environmental impact Control water intake and treated water quality > Identify radiological/chemical status Consideration on handling methodology > Consideration on approaches to tackle core structures Large increase of analysis needs anticipated
□ Capacity of human resource and facility/equipment has to be expanded.
Number of professional staff - recruitmentんA Capability of skilled staff - training A On-site facility, JAEA (several facilities), and private corporations are continuously available; in addition, two facility plans are on going at 1F site. ▷ Adequate deployment of facilities with analyzing capacity is required. Requires constant analysis of water characteristics