Radioactive water accumulating in Japan’s crippled Fukushima nuclear power plant may start overflowing from service trenches in three days, potentially increasing the contamination from the worst nuclear crisis since Chernobyl in Ukraine.

Tokyo Electric Power Company (Tepco) has been manually pumping water into overheating reactors after cooling systems broke down and much of that has overflowed into basements and trenches. The water is rising at a rate that means it will overflow as early as Monday, Bloomberg calculations from the company’s data show.

“There is still a risk of radioactive water leaking into the sea,” Tepco official Hikaru Kuroda said yesterday. “We may have about between five and seven days before the water levels reach the top of the trenches.”

Almost 60 percent of Japanese adults worry they have been contaminated since Fukushima started emitting radiation in March, according to a Pew Research Center poll.

The poll shows at least 80 percent of the population is dissatisfied with the response either from Tepco or the government of Prime Minister Naoto Kan, who survived a vote of no confidence yesterday.

“Solving the problem of contaminated water is critical,” said Tetsuo Ito, the head of the Atomic Energy Research Institute at Kinki University.

Meanwhile, Tepco shares rose 2 percent to ¥30 (R2.51) in Tokyo yesterday. The stock has fallen 86 percent since March 10, the day before an earthquake and tsunami knocked out power and cooling at the Fukushima Dai-ichi plant, erasing ¥3 trillion of the company’s market value.

Tepco has pumped millions of litres of cooling water into the three reactors that melted down. By May 18, almost 100 000 tons of radioactive water had leaked into the basements of reactor and turbine buildings, connecting tunnels and service trenches at the plant, Tepco estimates.

Water levels were between 28cm below the top of a shaft leading to a trench connected to the number 2 building and 24cm below the ground at the number 3 unit yesterday, Tepco general manager Junichi Matsumoto said. The levels were 64cm for the number 2 building and 46cm for number 3 on Friday last week.

To prevent leakage into the ocean, Tepco had poured concrete and gravel to seal trenches closest to the sea near the number 2, 3 and 4 reactors, spokesman Takeo Iwamoto said. “We are still considering the measures to be taken if contaminated water leaks.”

The contaminated water was a “massive problem”, Tetsuo Iguchi, a specialist in isotope analysis and radiation detection at Nagoya University, said last week. Tepco had to ensure the contaminated water did not get into the soil, Iguchi said.

The rate of increase in water level quickened because of three days of rain from the typhoon Songda that weakened as it swept past Japan earlier this week. Namie, a town near the Fukushima Dai-ichi station, had 112mm of rain on Monday, according to the Japan Meteorological Agency.

Japan is regularly buffeted by typhoons and tropical storms between May and October, adding another risk to containing the radiated water at the Fukushima station. Hydrogen explosions at the plant blew the roofs off three reactor buildings, exposing pools containing spent fuel rods.

Tepco spokesman Takeo Iwamoto said it was planning to complete installing covers for the buildings by October.

In early April, Tepco spent days trying to stop a leak of highly radioactive water into the sea from a pit near the number 2 reactor. It used concrete, sawdust, newsprint and absorbent polymer, used in nappies, to block the leak.

The efforts failed and drew comparisons with BP’s attempts to plug an oil leak in the Gulf of Mexico last year with golf balls and strips of rubber tyres. The Tepco leak was eventually sealed with sodium-silicate, known as liquid glass.

Tepco said in April that it had dumped almost 10 million litres of radioactive water into the sea from the Fukushima plant, which led to radioactive cesium being found in fish at levels exceeding health guidelines.

The firm said at the time the decision was the lesser of two evils as it needed to find space for storing water that was highly radioactive and more toxic than what was released into the sea. – Bloomberg