Japanese nuclear reactor that restarted 13 years after Fukushima disaster is shut down again

MARI YAMAGUCHI
Sun, November 3, 2024 

This photo shows the Onagawa nuclear power plant, operated by Tohoku Electric Power Company, Inc., in Onagawa, northeastern Japan, Thursday, Oct. 24, 2024. (Juntaro Yokoyama/Kyodo News via AP)


TOKYO (AP) — A Japanese nuclear reactor that restarted last week for the first time in more than 13 years after it had survived a massive 2011 earthquake and tsunami that badly damaged the nearby Fukushima nuclear plant was shut down again Monday due to an equipment problem, its operator said.

The No. 2 reactor at the Onagawa nuclear power plant on Japan’s northern coast was put back online on Oct. 29 and had been expected to start generating power in early November.

But it had to be shut down again five days after its restart due to a glitch that occurred Sunday in a device related to neutron data inside the reactor, plant operator Tohoku Electric Power Co. said.


The reactor was operating normally and there was no release of radiation into the environment, Tohoku Electric said. The utility said it decided to shut it down to re-examine equipment to address residents' safety concerns. No new date for a restart was given.

The reactor is one of three at the Onagawa plant, which is 100 kilometers (62 miles) north of the Fukushima Daiichi plant where three reactors melted following a magnitude 9.0 earthquake and tsunami in March 2011, releasing large amounts of radiation.

The Onagawa plant was hit by a 13-meter (42-foot) tsunami triggered by the quake but was able to keep its crucial cooling systems functioning in all three reactors and achieve their safe shutdowns.

All of Japan’s 54 commercial nuclear power plants were shut down after the Fukushima disaster for safety checks and upgrades. Onagawa No. 2 was the 13th of the 33 still useable reactors to restart.

Japan's government last year adopted a plan to maximize use of nuclear energy and is pushing to accelerate reactor restarts to secure a stable energy supply and meet its pledge to reach carbon neutrality by 2050.

Concern about the government’s revived push for nuclear energy grew after a magnitude 7.5 earthquake hit Japan’s Noto Peninsula on Jan. 1, 2024. killing more than 400 people and damaging more than 100,000 structures. It caused minor damage to two nearby nuclear facilities, and evacuation plans for the region were found to be inadequate.

Robot retrieves first piece of melted fuel from damaged Fukushima nuclear reactor

Interesting Engineering
Sun, November 3, 2024


A remote-controlled robot has retrieved the first piece of melted nuclear fuel from the Fukushima nuclear power plant. The piece will now be analyzed to assess how radioactive materials at the site have degraded over time.

This is the first time the fuel has been assessed since the 2011 meltdown and the latest in a line of robotic explorations into the reactor over the last few years. The robot was sent into the reactor under the instruction of Tokyo Electric Power Company Holdings, which manages the plant.

The "Telesco" robot collected the fuel using a fishing rod-like appendage and successfully returned the sample for further study. According to reports, the robot collected a sample roughly the size of a piece of gravel, or 0.2 inches (5mm) in diameter, weighing about 3 grams (0.1 ounces).

The sample was collected from a mound of molten fuel debris from the base of Fukushima's reactor number 2's primary containment vessel. The fuel sample was then transferred to an enclosed container after retrieval by workers in full HAZMAT gear.
The sample will now be analyzed

This is only the first step in the process, however. The sample will be assessed to see if its radioactivity is below a standard. If not, the robot must return to the reactor to collect another sample.

According to reports, TEPCO team members are confident that the current sample is sufficient to make such an assessment. The sample-taken exercise began in August and was supposed to be concluded within a fortnight.

https://www.youtube.com/watch?v=-ZJiVQ61MpQ

However, technical issues delayed the robot's deployment into the reactor until Saturday (November 2). The first issue was a procedural mishap that held up the operation for around three weeks.

But the robot's woes didn't end there. During its next attempt, its twin cameras failed to provide first-person views of its environment, requiring the robot to abort its mission to replace the cameras.

Part of the cleanup process

The Fukushima Daiichi nuclear power plant lost its essential cooling systems during the earthquake and tsunami of 2011. This disaster resulted in meltdowns in three of its reactors. Approximately 880 tons of dangerously radioactive molten fuel are still present in these reactors.

To this end, TEPCO has conducted several robotic probes to determine how to decommission the plant safely.

On Wednesday, Telesco successfully extracted a piece from a designated area directly beneath the Unit 2 reactor core. According to TEPCO, this location is significant as it was where large amounts of melted fuel fell during the meltdown 13 years ago.

Plant chief Akira Ono stated that only the tiny sample could provide crucial data to plan the decommissioning strategy. This will include developing necessary technology and robots and retrospectively learning how the accident occurred.

The Japanese government and TEPCO have set a target of 30 to 40 years for the cleanup, but experts believe this timeline is overly optimistic and needs reassessment. No specific plans have been made to remove fuel debris at the time of writing.