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Robots to probe Fukushima No.1 reactor from Jan.

Thursday, Nov. 25, 2021

NHK has learned that the operator of the Fukushima Daiichi nuclear plant plans to start a delayed robot survey of a damaged reactor from mid-January.

Officials of Tokyo Electric Power Company say preparations are well under way to send submersible robots inside the containment vessel of the No.1 reactor.

The probe is part of efforts to remove molten fuel debris from the reactor that suffered a meltdown accident due to the 2011 earthquake and tsunami.

The utility originally planned to start the robot survey of the reactor in 2019.

It has been postponed because preparations, such as making a hole in the door of the vessel for the robots to go through, have taken time.

The officials say they are now installing equipment to remotely control the robots, and expect to carry out a survey for more than six months from mid-January.

They plan to use a total of six robots with different functions to find and examine nuclear debris, or deposits of a mixture of molten fuel and reactor parts, inside the containment vessel.

The robots will use ultrasonic devices to locate and measure how much debris there is, and how thick the deposit is. They are also expected to collect a small amount of samples.

Previous surveys at the plant confirmed the presence of deposits believed to be fuel debris in the No.2 and No.3 reactors, which also suffered meltdowns, but not in the No.1 reactor.

November 26, 2021 Posted by | Fukushima 2021 | , , | Leave a comment

TEPCO to start ocean investigation by the end of the month.

November 26, 2021

On April 25, it was learned that Tokyo Electric Power Company (TEPCO) has decided to start an oceanographic survey by the end of the month to lay an undersea tunnel for the release of treated water from the Fukushima No. 1 Nuclear Power Plant. After completing the survey, the company will start laying the tunnel, aiming to start releasing the water in spring 2023. According to the officials, TEPCO had initially expected to start the survey in September, but was forced to postpone it due to difficulties in forming a consensus with neighboring municipalities.

In August, TEPCO announced a process plan to construct an undersea tunnel, run pipes through it, and drain the water into the sea about one kilometer offshore from the plant. In this submarine survey, in addition to magnetic surveys to ascertain the condition of the seabed, including confirmation of unexploded ordnance and other hazardous materials, diving surveys will be conducted as necessary. A submarine boring survey using a workboat will also be conducted.

The submarine tunnel is expected to be about 2.5 meters in diameter, and pipes will be cut through the bedrock of the seabed from the vicinity of the No. 5 and No. 6 reactors at the plant. We had considered the idea of draining the water into the sea near the east side of the plant, but we chose to go offshore where the tritium contained in the treated water would be more diffused. It is believed that the decision was based on the fact that there are no fishing rights in the waters about one kilometer offshore and that there would be little opposition from fishermen concerned about harmful rumors.

On the 17th of this month, the government announced the results of its assessment that the radiation dose in the surrounding waters due to the release of treated water was far below the safety standards set by the government and international organizations, and that the impact of radiation on the surrounding residents and the environment was “extremely minor.

The decision to release the treated water was made in April this year by the then government of Yoshihide Suga, and Prime Minister Fumio Kishida, who inspected the plant in October, said that it was a very important issue that could not be postponed.

November 26, 2021 Posted by | Fukushima 2021 | , , , | Leave a comment

Part of the frozen soil barrier may have thawed at the Fukushima Daiichi Nuclear Power Plant. Steel pipes are being driven into the ground to stop groundwater flow.

Nov. 25, 2021
Tokyo Electric Power Company (TEPCO) announced on November 25 that it may have thawed part of the frozen soil barrier wall built around the No. 1 to No. 4 reactors at the Fukushima Daiichi Nuclear Power Plant (Okuma and Futaba towns, Fukushima Prefecture) to prevent the inflow of groundwater. The company has announced that it will try to stop the flow of water by driving several steel pipes into the wall. The project will start as early as early December, and if the temperature in the ground continues to rise, additional steel plates will be driven in.
 According to TEPCO, a thermometer installed in the ground at the intersection of the southwest side of Unit 4 and the underground tunnel for drainage confirmed that the temperature exceeded zero degrees Celsius in late August. Since late September, the temperature has sometimes been above 10 degrees Celsius. A spokesperson explained at a press conference that the groundwater level outside the wall was high, and water pressure may have created a water path.
 The steel pipe is 35 centimeters in diameter and up to six meters long. Nine of them will be driven into the ground outside the frozen soil wall, which may have thawed, to create a wall three to four meters wide.
 The freezing wall, which has been in operation since 2017, was built to prevent groundwater from flowing into the reactor building, where melted nuclear fuel (debris) remains from the accident, and to reduce the amount of contaminated water generated. The wall is about 1.5 kilometers long. About 1,600 freezing pipes (30 meters long) were driven into the ground. The freezing pipes are about 1,600 tubes (30 meters long) driven into the ground and circulated with a cooling liquid of 30 degrees Celsius to freeze the surrounding soil. (Kenta Onozawa)

November 26, 2021 Posted by | Fukushima 2021 | , , | Leave a comment