Freezing out Fukushima's radioactive water

Japanese engineers face mammoth task of dealing with contaminated water from the nuclear plant disaster.

Tokyo, Japan - It's been more than three-and-a-half years since the earthquake and tsunami that rocked northern Japan in March 2011, crippling the Fukushima Daiichi nuclear power plant, a disaster that continues to unfold to this day.

Engineers at the Tokyo Electric Power Company (TEPCO), which owns the plant, still have a mammoth task in front of them: How to deal with millions of litres of water full of radiation resulting from the catastrophe.

The plant site, badly damaged by hydrogen explosions and reactor core meltdowns after the earthquake and tsunami, is glutted with steel storage tanks filled to capacity with contaminated water pumped out of the reactor facilities.

More than 1,000 tanks clog the site, and empty ones are being filled daily. As of September 23, the total volume of water stored had reached 583,000 tonnes, according to the Ministry of Economy, Trade and Industry (METI).

These tanks require regular monitoring, as leaks have occurred in the past, causing hundreds of tonnes of polluted water to spill out, some of it into the sea.

This watery nightmare is a result of the plant's location at the bottom of a hillside, between mountains and the Pacific Ocean. When it rains, much of the precipitation soaks into the soil, becomes groundwater, and runs downhill towards the sea.

Until recently, some 400 tonnes of groundwater flowed into the plant every day, mixing with highly radioactive coolant water collecting in the basements of the reactor buildings and adjoining turbine facilities.

To prevent the radiated water from running into the sea, TEPCO constantly pumps it out of the basements to a temporary storage facility. From there it passes through a water-decontamination system to remove caesium radionuclides.

The treated water is further processed through a desalination system, and a French-designed Advanced Liquid Processing System (ALPS) - that extracts more of the remaining multi-nuclides - before it is pumped into the storage tanks.

At the same time, TEPCO is injecting an additional 320 tonnes of partly cleansed and cooled water daily into the damaged reactor pressure vessels containing the melted nuclear cores to keep them from overheating. During the process, the water becomes contaminated and escapes through the damaged parts of the pressure and outer containment vessels and ends up in the basements, where it mixes with the incoming groundwater.

Stopgap battle

At best, then, TEPCO is fighting a stopgap battle just to maintain the status quo - a battle that has continued for the past three-and-a-half years.

The government has finally acknowledged the futility of this finger-in-the-dike operation, and last year it stepped in to oversee the plant's decommissioning.

"This decommissioning process is unprecedented. So we've solicited help from experts and companies on a worldwide basis," said an official who spoke only on background.

A number of plans have been devised to deal with the water crisis, the most prominent being the so-called "ice wall".

TEPCO is preparing to freeze the soil around the four damaged reactor buildings to create an impermeable, 1.5km barrier. "The frozen wall of soil will block the flow of groundwater," Mayumi Yoshida, a TEPCO official, told Al Jazeera. "The water will then flow around the perimeter and into the sea without becoming contaminated."

That's the plan, anyway. In principle, "it is possible to freeze the soil to a certain depth and certain length", Kazuaki Matsui, executive director of the Institute of Applied Energy, an independent research group in Tokyo, told Al Jazeera. "But I don't think we have any clear examples of freezing such a long wall, though that doesn't mean it's not possible. Certainly it's going to take a lot of energy [to operate], so it will be costly."

TEPCO said the technique is similar to that used in constructing ice-skating rinks. It has also been used many times in Japan during road and railway tunnel construction to preven.