Four of the plant’s six reactors became useless when sea water was used to cool them after the March 11 earthquake and tsunami knocked out generators running its cooling systems. The entire station north of Tokyo will likely be decommissioned, Japanese Prime Minister Naoto Kan said yesterday.

The damaged reactors need to be demolished after they have cooled and radioactive materials are removed and stored, said Tomoko Murakami, a nuclear researcher at the Institute of Energy Economics, Japan. The process will take longer than the 12 years needed to decommission the Three Mile Island reactor in Pennsylvania following a partial meltdown, said Hironobu Unesaki, a nuclear engineering professor at Kyoto University.

“Lack of public support may force the decommissioning of all six reactors,” said Daniel Aldrich, a political science professor at Purdue University in Indiana. Tepco “will try to salvage two if it can find public support, which may be unlikely.”

Kan yesterday blamed inadequate tsunami defenses at the plant for the world’s worst nuclear accident since Chernobyl in 1986, saying that the safety standards set by the utility known as Tepco were too low. Efforts to cool fuel rods at the four reactors have been hindered by detection of radiation levels that can prove fatal for a person exposed for several hours.

Tepco Can’t Comment

The utility is focusing on bringing the crisis at the Fukushima Dai-Ichi plant under control and can’t comment on the power station’s future, Naoyuki Matsumoto, a spokesman for Tepco, said by telephone yesterday.

Japanese authorities rated the Fukushima accident a 5 on the 7-step scale for nuclear incidents of the International Atomic Energy Agency, under which each extra point represents a 10-fold increase in seriousness.

At Pennsylvania’s Three Mile Island in 1979, one reactor partially melted in the worst U.S. accident, earning a 5 rating. Its $973 million repair and cleanup took almost 12 years to complete, according to a report on the World Nuclear Association’s website. More than 1,000 workers were involved in designing and conducting the cleanup operation, the report said.

Chernobyl Sarcophagus

Ukraine is unable to fund alone the cost of a new sarcophagus to cover the burned out reactor at Chernobyl, due to be in place by 2014. The 110 meter-high arched containment structure has a 1.55 billion euro ($2.2 billion) total price tag and the London-based European Bank for Reconstruction and Development has so far raised about 65 percent of that.

The Fukushima reactors may take about three decades to decommission, based on Japan’s sole attempt to dismantle a commercial reactor, said Murakami of the Institute of Energy Economics.

Japan Atomic Power Co. began decommissioning a 166-megawatt reactor at Tokai in Ibaraki Prefecture near Tokyo in 1998 after the unit had completed 32 years of operations, according to documents posted on the company’s website. The project will be completed by March 2021, or in 23 years, and cost 88.5 billion yen, the documents show.

Japan Atomic took three years through June 2001 to stabilize and remove nuclear fuels from the reactor core.

“It looks indisputable that Tepco will go ahead and dismantle the four reactors, and costs may exceed 1 trillion yen,” said Murakami, who worked at Japan Atomic for 13 years and was involved in the decommissioning of the Tokai plant. “Removing damaged fuels from the reactors may take more than two years, and any delays would further increase the cost.”