Japan’s Nuclear Damage Compensation and Decommissioning Facilitation Corporation (NDF) on 2 August made public its basic policy for recovery of melted nuclear fuel from units 1-3 at Tokyo Electric Power Company’s (Tepco’s) Fukushima Daiichi nuclear power plant.
Recovery will require advanced remote control technology and is also indispensable to implementing measures aimed at preventing further leak of nuclear materials. Tepco is scheduled to start recovery operations by 2021.
NDF’s policy would involve operations to insert a robot arm and other devices through the sides of the reactor vessels, remotely controlling the devices to collect debris.
NDF considered conducting similar operations by going in through the upper part of the container. However, it has decided to go through the side of the vessel, which is nearer to the bottom of the reactor. In its examinations of the inner parts of the reactors, Tepco has repeatedly put in robots through their sides and has accumulated experience in this method.
The condition of the reactors remains unclear, and there is concern that damaged equipment could hamper robots. The inner parts of the reactors must be further inspected before the operations get underway.
Any errors in the decommissioning operation could further damage the reputation of Fukushima Prefecture, the paper says. The prefectural government and others have called for assurances regarding the safety of decommissioning and disclosure of accurate and pertinent information.
The amount of contaminated water stored in some 900 tanks at the nuclear plant has continued to increase and currently stands at around 1m tonnes. About 80% of the total is to be disposed of by purification equipment which removes everything except tritium. The debate is now continuing over the possible discharge of the tritiated water into the sea. There is a limit the number of storage tanks that can be built at the site and there is also concerns that an earthquake could damage these tanks. The Nuclear Regulation Authority has urged Tepco to discharge treated water into the sea so the risks involved in decommissioning can be decreased.
Meanwhile, Tepco has begun installing a cover that will protect the machine for removing fuel from the storage pool of unit 3 at the plant. Fabrication of the cover began in November 2013 and test-runs for its installation have been carried out since June 2016.
Photo: Cover being installed over unit 3 spent fuel pool in August (Credit: Tepco)