Tepco Completes Unit 3 Fuel Assembly Removal

The Tokyo Electric Power Company said that two years of work have culminated in the complete removal of nuclear fuel from Unit 3 at the damaged Fukushima Daiichi Nuclear Power Plant.

Fukushima Daiichi cleanupThe plant suffered devastating meltdowns in three of its six reactors after the Great East Japan Earthquake of 2011, which caused a massive tsunami to disrupt power that was responsible for keeping reactor cooling systems operable.

In the destructive days of the accident, hydrogen explosions in the reactor buildings added to the devastation in easily the worst nuclear power disaster since the Chernobyl Nuclear Power disaster of April 1986.

Work on fuel removal at the No. 3 reactor was hampered by toxically high radiation levels in the reactor building. It took years to plan the cleanup strategy and develop the equipment needed to clear away rubble and fuel. Tepco utilized a custom-built crane to lift the fuel out of what remained of the Unit 3 cooling pool. The crane was operated remotely from a site over 540 yards away from the pool.

Among other difficulties, the extreme heat and violence of the explosions had damaged some of the handles that are normally used to lift fuel assemblies. Workers pulled the final group of six assemblies from the pool on 28 February, Tepco said. Attesting to the difficulty of the task, it took two years to remove the other 560 assemblies the pool contained.

Preparations for fuel removal were included clearing out the rubble, including damaged steel beams and the top floors of the reactor building. Tepco then constructed a dome to ensure that toxic debris and airborne radioactive material would not escape the clean-up site.

It was also a project of trial and error, Tepco said. “This was the first time such methods were attempted and there were various problems that had to be overcome,” the company said.

Tepco also said the first of three fuel assembly pools to be fully unloaded would be highly informative for the removal of fuel from the two other damaged units, which include about 1,000 additional fuel assemblies. Obstacles ahead include a large amount of rubble interfering with cleanup of Unit 1 and extremely high levels of radioactivity creating a toxic environment at the damaged Unit 2.

Additionally, removal of 1,533 fuel assemblies from the undamaged Unit 4 reactor was completed in 2014. Plans call for fuel removal to start at Unit 2 as early as 2024 and as late asd 2026, while the same will begin at Unit 1 as early as 2027 and as late as 2028. There are 392 fuel assemblies remaining in Unit 1 and 615 remaining in Unit 2. There is also an estimated 800-900 tons of melted fuel that has dropped to the bottom of the three damaged reactor cores.

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