A state-backed entity said Monday it has finalized an initial plan on how to extract melted fuel from the three crisis-hit Fukushima nuclear reactors.
The debris extraction plan will be used as a starting point for the government and the plant operator Tokyo Electric Power Company Holdings Inc. to determine specific approaches for each reactor by the end of September.
The extraction of the melted fuel from the Nos. 1-3 units at the Fukushima Daiichi nuclear complex, which suffered meltdowns following the massive 2011 tsunami and earthquake disaster, is seen as the most difficult step toward the ultimate goal of decommissioning the entire complex.
Tepco will also review, for the first time since June 2015, the road map for decommissioning the plant which is expected to take at least 30 to 40 years to complete. Extraction work is scheduled to start in 2021.
The Nuclear Damage Compensation and Decommissioning Facilitation Corp. said it plans to remove the melted fuel by partially filling the three reactors with water to cover some of the nuclear debris while allowing access to carry out the work.
The entity revealed the plan at a meeting of the Ministry of Economy, Trade and Industry in Iwaki in Fukushima Prefecture.
Using a remotely controlled apparatus, the debris is likely to be shaved off gradually with a drill or laser.
Some of the debris not submerged in water would likely be thrown into the air during the operation, posing a major challenge to efforts to mitigate the escape of radioactive material.
The entity tasked with providing technical support for decommissioning the complex has also considered a strategy which would see the containment vessel fully filled with water, as water is effective in containing radiation, but it has passed on the idea as the reactor containers are believed to have been damaged and would leak.
The containment vessel houses the reactor pressure vessel, a container that is designed to hold the fuel.
Following a magnitude-9.0 earthquake in March 2011, tsunami inundated the six-reactor plant, located on ground 10 meters above sea level, and flooded power supply facilities. Reactor cooling systems were crippled and the Nos. 1 to 3 reactors suffered fuel meltdowns, while hydrogen explosions damaged the buildings housing the Nos. 1, 3 and 4 units.
The Nuclear Damage Compensation and Decommissioning Facilitation entity was established after the Fukushima crisis, the worst nuclear disaster since Chernobyl, to help the utility pay damages. The state-backed entity holds a majority stake in the operator.
© Kyodo News International, Inc., source Newswire