Tokyo Electric Power Company (Tepco) estimates that JPY1370 billion or $12.6 billion will be required over the next 12 years to remove melted nuclear fuel from reactors at the Fukushima Daiichi nuclear power plant.
Tepco’s estimate covers only two of the three reactors (units 2 &3) that suffered core meltdown following the March 2011 earthquake and tsunami. No estimate was attempted for the cost to prepare for removal of melted nuclear fuel from Fukushima Daiichi 1, which presents a more complex problem.
Tepco has already released its plan for decommissioning the three reactors, which foresaw a start to removing melted nuclear fuel from unit 2 before the end of 2021, while removal would begin for unit 3 by 2031.
In announcing its expected profits for the current fiscal year, Tepco also outlined its estimated expenses for melted fuel removal over the next 12 years. Of the total, JPY350 billion will be applied as a special loss to the company’s balance statement for the fiscal year ending 31 March 2020.
Tepco estimates some JPY330 billion would be needed for preparatory measures, such as further examining the interior of Fukushima Daiichi unit 2 and decontaminating radiation from the area around all three reactors.
Another JPY20 billion is estimated for a trial removal of melted nuclear fuel from unit 2, and JPY1020 billion to construct the facilities needed to remove the melted fuel from units 2&3. The construction cost would be written off as a special loss from Tepco’s balance statement in the fiscal year when the work takes place.
Tepco forecast a net profit of JPY79 billion for the current fiscal year, down 66% from fiscal 2019. Sales are expected to decrease by 2.2% to JPY6199bn, it said.Fukushima contaminated water treatment options
Also on 30 March, Tepco released a report on two possible methods for disposing of treated contaminated water currently being stored at the Fukushima site.
The two options are discharge of the water into the sea or through vapour release.
As of mid-March, some 1.19 million cubic metres of treated water was stored in 979 tanks at the Fukushima Daiichi site. This included: water that has been treated by the Advanced Liquid Processing System (ALPS), as well as water treated to remove strontium. However, the average tritium concentration of the stored water is approximately 730,000 becquerels per litre.
A Japanese government subcommittee examined five options for dealing with contaminated water: geosphere injection, discharge into the sea, vapour release, hydrogen release, and underground burial. Of these, geosphere injection, hydrogen release and underground burial were considered to pose too many problems with regard to regulations, technology and time.
"For these reasons, discharge into the sea and vapour release are the practical options, both of which have precedent in current practice," the subcommittee concluded. It noted that the radiation impact of both options is "notably small, compared to natural radiation exposure".
Tepco’s own conceptual study on the two disposal methods also covers other remedial measures being taken. "Regardless of the disposal method, Tepco will not only comply with legal requirements but will also take initiatives to suppress reputational damage," it said.
Tepco said that the annual tritium release rate "will be set by referencing those of the existing nuclear facilities and making effective use of the period of 30 to 40 years required for decommissioning, instead of releasing a large amount at once."
Tepco said the tritium concentration would be as low as possible and that the amount of other radioactive materials in the water released would be reduced as much as possible.
For vapour release, Tepco said it would study dilution of tritium at a rate equivalent to that for discharge into the sea, as against the regulatory concentration limit of tritium in the atmosphere (5 Bq in 1 litre of air).
For discharge into the sea, the company will study dilution rates of tritium with reference to operational standards for 'groundwater bypass' and 'subdrains' (1500 Bq in 1 litre of water). These are well below the regulatory concentration limit for tritium in seawater (60,000 Bq in 1 litre of water).International perspective
An International Atomic Energy Agency (IAEA) team of experts reviewed progress made by Japan in preparing for a decision on how to dispose of the treated water.
The team, which published a report on 2 April, concluded that both options for controlled disposal were "technically feasible" and are both "routinely used" by operating nuclear power plants worldwide.
The IAEA team said Japanese subcommittee’s recommendations to the government were based on a “comprehensive and scientifically sound analysis addressing the necessary technical, non-technical and safety aspects."
The final decision on which option will be taken, rest with the Japanese government. However, the IAEA says it is ready to work with Japan to provide radiation safety assistance before, during and after the disposition, once the route is decided.
Management of contaminated water at the Fukushima Daiichi site is seen as one is one of the most important decommissioning tasks, and has been under discussion since 2013. The total tank storage capacity, which will reach 1.37 million cubic meters by the end of 2020, is expected to be full around the summer of 2022.
Photo: Tanks storing contaminated water at Fukushima Daiichi nulcear power plant (Credit: Tepco)