Japan has pledged more than £300m to contain leaks and decontaminate radioactive water from the Fukushima nuclear plant.
Chief Cabinet Secretary Yoshihide Suga told a news conference today that the government would spend a total of 47bn yen (£304m), including 21bn yen in emergency reserve funds from this year's budget.
Of that, 32bn yen will fund the building of a massive underground wall of frozen earth around the damaged reactors to contain groundwater flows, and 15bn yen to improve a water treatment system meant to drastically reduce radiation levels in the contaminated water.
"The world is watching to see if we can carry out the decommissioning of the Fukushima nuclear power plant, including addressing the contaminated water issues," Prime Minister Shinzo Abe told cabinet ministers, who met to approve the plan.
Operator Tokyo Electric Power Co (Tepco) is storing enough contaminated water to fill more than 130 Olympic-sized swimming pools, mostly in hastily built tanks that officials have said may spring further leaks.
Since the government announced they would step in yesterday, Tepco has found a new area of high radiation with a reading above 100 millisieverts per hour, though the reading is imprecise as workers were using instruments that only recorded radiation up to 100 millisieverts. Japanese nuclear workers are limited to a cumulative exposure of 100 millisieverts over five years.
Trade and Economy Minister Toshimitsu Motegi, who yesterday accused Tepco of “playing a game of whack-a-mole” with problems at the site, told reporters the wall of frozen earth is designed to prevent groundwater entering a maze of basements and trenches beneath the reactors and mixing with water being used to cool melted fuel rods.
But the concept of freezing earth to block water flows is a technology commonly used in digging subway tunnels – untested on the Fukushima scale and the planned duration of years or decades.
Professor Neil Hyatt, professor of Radioactive Waste Management at the University of Sheffield, said: “The idea of the freeze wall concept is to chill a salt water solution below the melting point of ice and then pump this through underground pipes. This causes the local groundwater to freeze, forming a barrier to the movement of contaminated ground water.
“A similar process is used in underground uranium mining, to prevent flooding of a working area at depth, so the basic engineering principles are quite well understood. However, this is a very energy intensive process to maintain, so there will need to be careful design and trial work to produce an effective barrier that minimises energy demand.
“The urgent challenge, in terms of reducing the on-site hazard of radioactive water storage, is to deploy additional decontamination units so the water can be discharged under environmental regulations.
“Then, the material in the decontamination units themselves will require stabilisation, for example as a glass or ceramic, in order to be suitable for long-term storage.”
But the water decontamination technology, developed by Toshiba and US-based EnergySolutions, in use at the plant has repeatedly suffered from glitches.
The Advanced Liquid Processing System (ALPS) can remove all radioactive particles from water except tritium – considered the least harmful to humans – but the system has been stalled for months due to mishaps prompting the government’s decision to commit 15bn yen to install a second water filtering system, similar to ALPS, in the year from next April.
Critics have said the government is mainly trying to cool down international media coverage ahead of the International Olympic Committee’s decision over whether Tokyo – 140 miles from the wrecked plant – will host the 2020 Olympic Games.
But the government intervention represents only a tiny slice of the response to the Fukushima crisis triggered by the March 2011 earthquake and tsunami that caused reactor meltdowns at the plant as the clean-up, including decommissioning the ruined reactors, will take decades and rely on unproven technology.
The ultimate fate of the plant's operator also remains unclear, as does the question of who will eventually foot the bill – Japanese taxpayers, or the embattled Tepco.
"This is a matter of public safety, so the country has to take the lead on this issue and respond as quickly as possible. Figuring out who to bill for the costs can come later," Economics Minister Akira Amari told a news conference.
FACTBOX: The Advanced Liquid Processing System (ALPS)
• Radioactive materials are filtered out of contaminated water as it flows through 14 steel cylinders that contain active carbon, artificial minerals and other absorbents
• Waste materials like the absorbent and remaining sludge are transferred to high-integrity containers (HICs) that are transported to a temporary storage facility
• Tepco said last year highly radioactive waste would need to be stored for around 20 years in HICs
• The three lines of ALPS have the capacity to treat up to 1,500 tonnes of contaminated water every day
• ALPS was installed at Fukushima in August-September last year, but did not begin "hot tests" until the end of March
• The International Atomic Energy Agency said in April that the system still had not "accomplished the expected result of removing some radionuclides" in tests, and noted Tepco needed to develop long-term storage plans for waste created by treating water
• On 4 April, the system shut down for an hour due to an operator error
• On 15 June, a Tepco worker found a leak at the bottom of one of the tanks in an ALPS line prompting Tepco to halt the system again for inspections, which found signs of corrosion in the stainless steel tanks