New proposal suggests removing Fukushima plant’s melted nuclear fuel from side — The Mainichi

” A method to remove melted nuclear fuel debris on the bottom of the containment vessels of Fukushima No. 1 Nuclear Power Plant’s first, second and third reactors from the side was proposed by the Nuclear Damage Compensation and Decommissioning Facilitation Corporation (NDF) on July 31.

Hajimu Yamana, head of the NDF, which is tasked with considering how to remove fuel debris from the reactors, for the first time explained the organization’s specific method proposal to the heads of local governments at a countermeasures for the decommissioning and handling of the contaminated water council meeting held in Iwaki, Fukushima Prefecture.

The method would focus on prioritizing the removal of debris from the bottom of the vessels from the side, using robotic arms and other remote devices while flushing water over the debris. However, ways to block radiation and countermeasures against the scattering of airborne radioactive dust still remain unsolved. The central government and Tokyo Electric Power Co. (TEPCO) plan to finalize their policy to remove the debris and amend the decommission schedule in September.

In all three of the reactors, contaminated water has collected at the bottom of the containment vessels. The NDF had previously considered a “flooding method” that would fill the containment vessels completely with water to block radiation from leaking. However, measures to repair the containment vessels and prevent leakage of the radioactive water would be difficult, so the plan was put aside for having “too many issues.” “

by The Mainichi


Fukushima government objects against building sarcophagus on Fukushima plant — Fukushima Diary

” Two days before, Nuclear Damage Compensation and Decommissioning Facilitation Corporation released the new plan on Fukushima plant decommissioning. In this new plan, building a stone coffin to cover the reactor buildings like Chernobyl nuclear power plant was mentioned.

Uchibori, the governor of Fukushima prefecture officially objected to the government of Japan and demanded to remove nuclear fuel debris and dispose it outside of Fukushima plant instead of sarcophagus.

The governor commented building a sacrophagus in Fukushima is “unacceptable”. Fukushima prefecture would have to give up returning the residents and it would also affect the harmful rumor.

Takagi, Senior Vice-Minister of METI and Nuclear Damage Compensation and Decommissioning Facilitation Corporation apologized and stated they have never considered sarcophagus and will try to complete the removal of all nuclear fuel debris in Fukushima plant. ”

by Iori Mochizuki


Japan to start Fukushima fuel debris retrieval in 2021 — World Nuclear News

” Japan expects to start the retrieval of fuel debris from the Fukushima Daiichi nuclear power plant in 2021, the executive director of the Nuclear Damage Compensation and Decommissioning Facilitation Corporation (NDF) said yesterday. Three of the plant’s six reactors suffered core meltdowns in the March 2011 accident, leaving melted nuclear fuel debris on the floor of their containment vessels.

NDF was established in September 2011 by the Japanese government and the country’s nuclear power plant operators to manage a fund to support operators in providing compensation to victims of nuclear accidents. Although established following the Fukushima Daiichi accident, NDF will continue to be maintained in the future as part of the Japanese nuclear liability regime.

“We expect to select the retrieval method within the next few years, after which detailed design and mock-up tests will follow,” NDF executive director Yasuharu Igarashi told delegates at the VII Atomexpo conference in Moscow. The event was hosted by Russian state nuclear corporation Rosatom. “For the start of retrieval of fuel debris, we are now thinking 2021,” Igarashi said.

NDF has identified three “priority methods” for retrieving highly radioactive nuclear fuel debris in three reactors at Tokyo Electric Power Company’s (Tepco’s) Fukushima Daiichi plant. They are: submersion; partial submersion top access; and partial submersion side access. The first two rely on the removal first of core internals above fuel debris, while the third requires that the reactor pressure vessel pedestal exterior component inside the primary containment vessel (PCV) and interference have first been removed.

The submersion method would remove the debris in a submerged condition, with the containment vessel filled with water to shield against radiation and prevent the spread of radioactive materials during the retrieval process. The reactor damage would need to be accurately identified and repaired before water is poured in. Partial submersion means that water would only be used when the debris has been separated from the vessel floor. The debris would be removed from either the top or the side of the vessel. This method would require continuous cooling of the retrieved debris and measures to prevent radioactive materials from scattering.

Tepco started inspections of unit 1 of the plant in April using robots mounted with cameras and radiation-measuring equipment. The shape-changing robot began surveying conditions within the PCV of the damaged unit on 10 April. However, the robot stopped working before completing its mission. The robot was developed by the International Research Institute for Nuclear Decommissioning and Hitachi-GE Nuclear Energy to investigate hard-to-access areas of the plant. Tepco later sent in a second robot On April 20. The company said that it had decided not to try to retrieve a second robot dispatched inside the unit to avoid it becoming blocked and impeding future missions.

Igarashi said that NDF is following five “guiding principles” for risk reduction in its strategic plan for decommissioning the Fukushima Daiichi plant. They are that the plan is safe, proven, efficient, timely and “field-oriented”, meaning it is based on the actual conditions of the site and structures.

“The decommissioning of the Fukushima Daiichi nuclear power plant is a continuous risk reduction activity to protect people and the environment from the risk of radioactive materials resulting from the severe accident,” he said. “A risk reduction strategy along a mid- to long-term timeline will be designed in NDF’s strategic plan.”

The structure of NDF’s risk management strategy is to be completed by 2017, he said.

In addition to fuel debris retrieval, the strategic plan will also include a policy for waste management involving storage, processing and disposal methods, he said.

NDF has reviewed international standards for waste management, he said, and the International Atomic Energy Agency’s General Safety Requirements Part 5 and Specific Safety Requirements-5 are “important references”. ”