Japan has pledged nearly $500m to contain leaks and decontaminate radioactive water from the Fukushima nuclear plant, crippled by an earthquake and a tsunami more than two years ago.
Nearly $32m will pay for the building of an underground wall of frozen earth around the damaged reactors to contain groundwater flows, and $15m to improve a water-treatment system meant to reduce radiation levels in the contaminated water.
Tuesday's announcement marks a jump in government efforts to cope with the legacy of the worst atomic disaster in a quarter of a century.
Freezing earth to block water flows is a technology commonly used in digging subway tunnels, but is untested on the Fukushima scale and the planned duration of years or decades.
Yoshihide Suga, chief cabinet secretary, said the government would spend $473.05m, including about $21m in emergency reserve funds from this year's budget.
"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," Shinzo Abe, the Japanese prime minister, told cabinet ministers who met to approve the plan.
The ultimate fate of the plant's operator, Tokyo Electric Power Co (Tepco), remains unclear, as does the question of who will eventually foot the bill - Japanese taxpayers or Tepco.
The clean-up, including decommissioning the ruined reactors, will take decades and rely on unproven technology.
"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," Akira Amari, Japan's economics minister, said.
Al Jazeera's Florence Looi, reporting from Tokyo on Tuesday, said the wall was just one part of the plan.
|Government steps in as Fukushima problems persist
"We have no way of knowing how long this wall needs to stay there," she said.
"The second part of the plan is to treat the highly contaminated water. This is water that has been used to cool the melted nuclear reactor cores.
"The plan is to treat this water and then eventually perhaps allow it to be discharged in to the sea. The problem with that is that the current technology that Tepco is using doesn't allow for all types of radioactive elements to be filtered out."
The latest government intervention represents only a tiny fraction of the response to the Fukushima crisis, caused by the March 2011 earthquake and tsunami, which caused reactor meltdowns at the plant.
Tuesday's announcement comes just days before the International Olympic Committee decides whether Tokyo - 230km from the wrecked plant - will host the 2020 Olympic Games.
The recent problems have revived notions, debated but rejected in the months after the March 2011 disaster, of liquidating Tepco or at least splitting off the Fukushima operation from its other businesses and putting it under direct government control.
Critics say the government is mainly trying to cool down international media coverage in advance of the Olympics decision.
The peak release of radiation in the sea around Fukushima came about a month after the earthquake and tsunami.
Ocean currents have since dispersed the plume and sent the diluted radiation in a slow drift towards the West Coast of the US, studies have shown.