Current State of Post-Accident Operations at Fukushima Daiichi Nuclear Power Station (Jun. to Dec. 2022)

State of the Plant Fukushima Now – Part 2, BY CITIZENS’ NUCLEAR INFORMATION CENTER APRIL 5, 2023 · By Matsukubo Hajime (CNIC)

The water temperature in the containment vessels and the spent fuel pools (SFPs) shows no great variation despite seasonal temperature changes. The state of releases of Xenon-135 (half-life roughly nine hours), released when uranium fuel undergoes fission, is also unchanged and it can therefore be estimated that the state of the reactors is stable. Further, according to an assessment by TEPCO in December 2022, around 10,000 becquerels per hour (Bq/h) of radioactive materials were being released to the atmosphere from the buildings (Fig.1 on original).

At the same time, decay heat has fallen greatly with the passage of time, and thus the volume of cooling water injected into the reactors has been reduced (falling from 7-10m³ per hour in May 2011 to 1.6-4m³ per hour as of December 2022).

The state of removal of spent nuclear fuel from the SFPs is summarized in Table 1 [0n original]. Spent nuclear fuel removal from Units 3 and 4 has been completed. However, as it has not been possible to remove control rods and other high-dose equipment stored in the SFPs, preparatory work has been underway for removal of this equipment from Unit 3 in the second half of FY2022 and removal from Unit 4 will commence in the second half of FY2024. Further, the removal of this equipment from Unit 3 was due to start from late October 2022, but this has now been rescheduled for early March 2023.

Preparations for the removal of fuel debris are also under way…………………………………..

The Unit 2 reactor core isolation cooling (RCIC) system was operating after the accident and for a further three days, including the time when the tsunami arrived at the plant. Uncovering the reason why it ceased functioning has been an issue, but it is inaccessible even now, after approximately 12 years underground………………………………………..

The changes in the average number of workers onsite per day is shown in Fig. 2 [on original] . As of December 2022, the number of workers was 4,410, about half the number it was at its peak. …………………………………

Contaminated water countermeasures at Fukushima Daiichi Nuclear Power Station (FDNPS) can be broadly divided into three areas: 1) Reduction of groundwater flowing into buildings, 2) Reduction of contaminated water flowing into the sea, and 3) Reduction of the toxicity of contaminated water. The main countermeasures to reduce water inflow into the buildings are, from higher elevations downward, ………………………………………………………

In the reduction of the toxicity of contaminated water, cesium and strontium are removed, and after the removal of impurities using a reverse osmosis (RO) membrane, radionuclides other than tritium are removed by the multi-radionuclide removal equipment…………………………………………

The frozen earth barrier consists of about 1600 30-meter freeze pipes buried in the ground, through which coolant at -30°C is circulated to freeze the surrounding soil. The effectiveness of the frozen earth barrier has been questioned since it was first installed, but since 2019 there have been several coolant leakage incidents.

Concerning the issue of releasing contaminated water into the ocean after ALPS treatment, TEPCO’s policy to release the water was authorized at the 25th Meeting of the Nuclear Regulatory Authority on July 22, and the construction was approved by the governor or Fukushima Prefecture and the mayors of both Okuma Town and Futaba Town in August. At present, construction of the release tunnel is ongoing, and the plan is to complete the construction during the first quarter of 2023. ………………………….. A fund of 30 billion yen has already been established as a measure against “adverse publicity.” Additionally, TV commercials, etc. are also being employed as “actions to foster understanding.” On the same day Chairman Masanobu Sakamoto of the National Federation of Fisheries Cooperative Associations released a statement saying, “We have not altered one little bit our opposition to the oceanic release.”

Meanwhile, Secretary General Henry Puna of the Pacific Islands Forum (PIF), an inter-governmental organization that aims to enhance cooperation among 15 countries and two regions of Oceania, announced in a statement on January 18 that PIF will demand a postponement of releases until it has become possible to confirm the safety of all involved [timetable of events shown on original] more https://cnic.jp/english/?p=6553