Nuclear fuel removal from Fukushima Daiichi nuclear power plant from Unit 2 Plan announcement August 8, 18:36
Regarding the removal of nuclear fuel that was melted down by the accident at the Fukushima Daiichi Nuclear Power Station, the specialized agency in the country that is considering the technical policy of decommissioning has started from Unit 2 where the situation inside the containment vessel is most known in the survey. Announced a plan to start. The government and TEPCO will finalize the policy of taking out during this fiscal year based on this content.
In Units 1 to 3 of the Fukushima Daiichi nuclear power plant that caused the meltdown, the so-called “fuel debris” containing melted nuclear fuel is thought to have reached the bottom of the containment vessel that covers the reactor.
Taking this out is the biggest difficulty in advancing the decommissioning, and the government and TEPCO are aiming to start taking it out in 2021. On this day, the “Nuclear Damage Compensation and Decommissioning Support Organization” created by the government to provide technical support for decommissioning announced a plan called a “strategic plan” on the 8th. We decided to start from Unit 2 little by little.
The reason for this is that the situation inside the containment vessel is best known in previous surveys, and that a route to put in the robot has been built, so that extraction can be started reliably while ensuring safety compared to other units. explained.
Also, regarding the nuclear fuel that has been taken out, it should be stored temporarily in an air-cooled state by creating a dedicated metal container, assuming that the temperature has dropped sufficiently because water has been poured into the containment container so far. It is said.
The government and TEPCO will finalize a policy on the removal of nuclear fuel that has melted during the current fiscal year, based on the plan of the Japan Nuclear Damage Compensation and Decommissioning Support Organization.
How to remove nuclear fuel
How to extract the melted nuclear fuel that emits strong radiation? This is considered the biggest difficulty in decommissioning.
What kind of take-out method can be considered in Fukushima Daiichi Nuclear Power Unit No. 2 where the proposal to start first was shown? The person in charge of the Ministry of Economy, Trade and Industry explained the inside of Unit 5 which has a structure similar to Unit 2 last month and does not cause meltdown.
The containment that covers the reactor is approximately 30 meters high. It is made of steel and has a thickness of around 3 cm. It is thought that “fuel debris” is accumulated in the bottom of the containment vessel.
The containment vessel has a work hole with a diameter of about 60 cm on the side, and in Unit 2, the radiation dose around the hole is relatively low and it is easy to secure a work place. It is said that it can be put inside.
There is an iron scaffolding in the containment, which is an obstacle to lowering the robot to the bottom. Previous investigations have revealed that Unit 2 has lost some of this scaffold due to the accident.
For this reason, a robot inserted through a work hole can approach the bottom of the containment vessel from a part without a scaffold, and it is possible to examine how to take out small amounts by grabbing or sucking off the melted nuclear fuel is.
Ministry of Economy, Trade and Industry Masanobu Kino Decommissioning and Contaminated Water Countermeasures said, “Unit 1 is in the investigation stage because the internal state is not well understood. I think that Unit 2 is easy to access. ”