The current water leaks at Fukushima nuclear plant in Japan have become worse, according to experts.

Tokyo Electric Power Co admitted that the 300-tonne leak is the fifth and most serious from a tank since the March 2011 disaster, when three of the plant’s reactors melted down after a huge earthquake and tsunami knocked out the plant’s power and cooling functions.

The underground seepage from the reactor and turbine building area is much bigger and possibly more radioactive, confronting the plant’s operator, TEPCO, with an invisible, chronic problem and few viable solutions, experts believe.

To keep the melted nuclear fuel from overheating, TEPCO has rigged a makeshift system of pipes and hoses to funnel water into the broken reactors.

The radioactive water is then treated and stored in the aboveground tanks that have now developed leaks.

But far more leaks into the reactor basements during the cooling process, then through cracks into the surrounding earth and groundwater.

About 1,000 tonnes of underground water from the mountains flows into the plant compound each day, of which 400 tonnes seep into the reactor and turbine basements and get contaminated.

The remaining 600 tonne avoids that area, but at least half of it is believed to eventually come in contact with contamination elsewhere before entering the sea, according to an estimate by Japan’s Agency for Natural Resources and Energy.

Al Jazeera's Anita McNaught, reporting from Naraha, said: "The Japanese government was hoping at least to contain the nuclear problem. It seems it can’t even manage to do that."

Scientists, pointing to high radioactive cesium levels in bottom-dwelling fish since the disaster, had for some time suspected the plant was leaking radioactive water into the ocean.

But TEPCO repeatedly denied that until last month, when it acknowledged contaminated water has been leaking into the ocean from early in the crisis.

Crisis started when the underground reservoir of contaminated water began spilling from the plant’s reactors after the 2011 earthquake and tsunami has been creeping towards the Pacific.

Source: Al Jazeera and agencies