With the decommissioning of Fukushima No. 1 proving harder than expected, planners have pushed back plans to remove spent nuclear fuel from the cooling pools perched above the damaged reactors by a few years.
The decision was made Friday by the government and Tokyo Electric Power Co., which runs the tsunami-hit complex.
The spent fuel rod assemblies must be removed from the pools above reactor Nos. 1, 2 and 3 before any attempt can be made to extract the fuel that melted inside the reactors themselves.
But the delay will not impact the overall cleanup timeline for the plant, which spans 30 to 40 years, the government and Tepco said.
The first revision to the decommissioning road map in two years was made after it was decided that too much priority had been placed on speed. This would have heaped excessive pressure on workers tasked with operating in a highly radioactive environment. The road map was first crafted in December 2011.
According to the revised road map, the removal of fuel assemblies from the No. 3 cooling pool will be delayed until fiscal 2017, as it is already behind schedule. The work was expected to be finished in the first half of fiscal 2015, which ends next March.
Work to extract fuel assemblies from the pools on units 1 and 2 is now expected to begin in fiscal 2020, instead of fiscal 2017.
The subsequent extraction of the melted fuel — the most challenging part of the process — is expected to start in 2021, but the government and Tepco have not yet figured out how to do it. They are aiming to settle on a single approach in fiscal 2018.
The revised road map also aims to reduce the amount of groundwater seeping into the structurally damaged plant to less than 100 tons per day in fiscal 2016, instead of 300 tons. The influx of groundwater has become its own crisis by mingling with the highly radioactive water generated in the daily process of cooling the leaking reactors. And all of it must be stored on site until it can be cleaned.
The most important progress made at the plant so far has been the removal of all the fuel assemblies that had been stored in the cooling pool above the No. 4 reactor, which suffered a hydrogen explosion but avoided meltdown.
The revision also said the government and Tepco will begin discussions in the first half of 2016 on how to dispose of water tainted with tritium. The filters currently available can remove all radioactive isotopes from large volumes of water with the exception of tritium, a common byproduct at nuclear plants.
The International Atomic Energy Agency and the Nuclear Regulation Authority have suggested such water be dumped into the ocean rather than be kept in tanks, to reduce the risk of accidents, but Tepco remains undecided on this given strong local opposition to the proposal, especially by fishermen.