Japan's nuclear regulator on Wednesday approved a plan for the embattled operator of the disaster-hit Fukushima nuclear power plant to start freezing soil around its battered reactor buildings, in a move to reduce the massive amounts of radioactive water accumulating in the buildings.

The Nuclear Regulatory Authority approved the plan for the reactor buildings, crippled in the wake of an earthquake-triggered tsunami in 2011, with the work expected to be carried out by the plant's operator, Tokyo Electric Power Co on Thursday.

Freezing will start with the soil on the east side of the reactor buildings, which face the Pacific Ocean, as well as the majority of the west side.

TEPCO believes the process will reduce the amount of groundwater flowing into four of its reactor buildings and reduce the amount of accumulated radioactive water, which is leaking into the ocean through drainage ditches. The leaks are a great concern, drawing condemnation from the international community.

The process is expected to last eight months, after which TEPCO said the volume of underground toxic water could be reduced dramatically from 400 tons to around 50 tons.

Plan criticized

The freezing of the entire 1.5-kilometer long wall will start in stages, TEPCO said, with each phase being overseen by the NRA and requiring prior approval, as the watchdog is concerned that rapidly dropping levels of groundwater within the ice wall, as the contaminated water is blocked, could lead to more radioactive leaks.

Construction of the ice wall was completed in February after two years of work involving driving steel pipes 30 meters into the soil around the perimeter surrounding the No. 1 to 4 reactors at the troubled plant. TEPCO will now inject liquid calcium chloride at minus 40 degrees Celsius into the pipes to freeze the surrounding soil, which, in theory, will prevent groundwater from mixing with coolant water that is becoming contaminated when it comes into contact with melted nuclear fuel.

The plan for the ice wall, the technique of which has been used previously in engineering projects, but not on a scale of the Fukushima plant or for the expected duration, has been met with some criticism by experts who believe capping the reactors in concrete, as was the case following the 1986 Chernobyl disaster, would be a more effective means of dealing with the ongoing crisis, which is the worst commercial nuclear disaster in history.

Huge challenge

The project is costing taxpayers around $309 million and NRA Chairman Shunichi Tanaka on Wednesday expressed some concerns.

He said that the project was and will continue to be a huge challenge and that the ongoing monitoring of the situation, a process TEPCO has over the past 5 years monumentally failed at, as well as informing the government and the public of radioactive leaks, gaffes and other mishaps, would need to be a priority.