Fukushima finishes purification process of stored radioactive water

The operator of the disabled Fukushima nuclear power plant in Japan has finished purifying the 620,000 tonnes of radioactive water stored in tanks at the plant, overcoming the main stumbling block in the process of dismantling it.

All the strontium in this stored water has been filtered out, the Tokyo Electric Power Company (Tepco) told Efe news agency on Wednesday.

This has greatly reduced the risk of radiation at the plant and of contamination should any of the containers leak.

Among several noxious liquid substances at the site, an isotope of strontium has been the major contributor to increases in radiation levels around the stricken plant.

Tepco said 30 percent of the 620,000 tonnes of radioactive water require additional treatment to remove other less harmful substances.

It had initially planned to eliminate all strontium by March this year but the process was delayed by a series of breakdowns.

The radioactive water, generated during a rapid cooling of the reactors after the earthquake and tsunami in 2011, has been a major problem for Tepco, particularly as the tanks containing it have leaked continuously.

The most serious leakage occurred in mid-2013, when about 300 tonnes of highly radioactive liquid escaped.

The gravity of that situation led the International Atomic Energy Agency and the Japanese authorities to re-classify the disaster to level 3 on the International Nuclear and Radiological Event Scale, the maximum level being 7.

Tepco will have to continue treating radioactive water at the plant, as it continues to generate around 400 tonnes every day.

This water is the result of leaks of the contaminated refrigerant used to keep the atomic reactors cool mixing with water flowing from natural aquifers penetrating into the basement of the buildings that house the plant.

Tepco hopes to treat the accumulated water in the basement with a procedure it is developing that involves freezing the ground around the buildings.