Major step forward for decommissioning, but operation is one of most technically challenging at Japan nuclear site
The long-running decommissioning effort at Japan’s Fukushima-Daiichi nuclear power station has reached an important milestone with the start of removal of nuclear fuel from the spent fuel pool of Unit 2.
The operation is one of the most technically challenging phases of the site’s decades-long cleanup programme following the catastrophic 2011 earthquake, tsunami and nuclear accident.
Owner and operator Tokyo Electric Power Company (Tepco) intends to complete the removal of all fuel assemblies from the Unit 2 pool by fiscal year 2028.
The Unit 2 reactor’s spent fuel pool currently stores 587 spent fuel assemblies, which are highly radioactive, and 28 unused fuel assemblies, according to Tepco. The unused fuel is being removed first because it poses a lower risk in the event of an accident.
Radiation levels at the Unit 2 reactor building are still high after the nuclear fuel in the reactor melted down in the March 2011 accident. Radiation on the fifth floor, where the fuel pool is located, measures as high as 3 to 5 millisieverts per hour, making it difficult for workers to stay there for a long time.
Tepco is using a remotely controlled crane to remove the fuel assemblies, which are placed one by one in a transport container called a cask inside the pool. The cask will be lifted out of the pool and then lowered onto a trailer from a platform installed next to the building.
The trailer carrying the cask will move to a common pool at the plant to cool and store the fuel.
Decommissioning Cost Estimated At $76 Billion
Since spent fuel continues to generate heat, it must be continuously cooled. At the time of the accident at the plant, the loss of power prevented the pools from being cooled, so Tepco injected seawater.
As the common pool has limited capacity, Tepco plans to transfer fuel that no longer generates significant heat to containers called dry casks, which can be cooled by air, in order to secure storage space in the common pool.
The Fukushima-Daiichi decommissioning programme remains one of the largest and most complex nuclear cleanup projects ever undertaken. The total cost has been estimated at $76bn (€65bn).
Significant progress has been made in stabilising the site since the 2011 disaster, but the removal of spent and unused nuclear fuel from reactor buildings remains a top priority due to the potential safety risks posed by fuel stored above ground in spent fuel pools.
Spent fuel has already been removed from pools at Units 3, 4 and 6 at the six-unit facility, with removal work underway at Unit 5. Tepco has said removal of spent nuclear fuel from the Unit 1 pool is scheduled to begin between 2027 and 2028.
