Nine months after the Daiichi nuclear power plant in Japan’s Fukushima Prefecture was rocked by a magnitude 9.0 quake and an ensuing massive tsunami that plunged it into the worst nuclear crisis since Chernobyl, 25 years earlier, Japan’s prime minister, Yoshihiko Noda, on Friday said in a televised address that the plant’s four afflicted units have been brought to a state of cold shutdown. However, the crisis is far from over, he said.

Daiichi’s owner, Tokyo Electric Power Co. (TEPCO), confirmed that Units 1, 2, 3, and 4 have been brought to a condition “equivalent to ‘cold shutdown,’” adding that, “in case an accident occurs, we will be able to keep the radiation dose at the site boundaries at a sufficiently low level.” Cold shutdown means that the reactor pressure vessels’ bottom temperatures and temperatures inside the primary containment vessels (PCVs) are below 100C.

TEPCO had in April released its so-called "Roadmap towards Restoration," a plan of action to ensure that radiation doses are in steady decline. The first three-month-long step started on March 11—the day of the quake—and entailed trying to prevent additional hydrogen explosions inside the reactor PCVs through injection of nitrogen to keep the concentration of hydrogen and oxygen below flammability limits. The second step, spanning three to six months, entailed ensuring that the release of radioactive materials is under control. The third step foresees TEPCO maintaining and protecting the reactors in cold shutdown within three years.

“At the first ‘Government and TEPCO’s mid-to-long term countermeasure meeting’ today, the ‘Mid-and-long-Term Roadmap towards the Decommissioning of Fukushima Daiichi Nuclear Power Units 1-4, TEPCO’ was approved officially,” TEPCO said in a statement today. “This means we will take the first step toward the completion of the decommissioning over the next forty years.”

TEPCO said its plans will now shift from stabilization of the plant to the maintenance of stable condition. “Therefore, we will take several countermeasures such as the removal of the spent fuel from the pool, the removal of fuel debris and so on.”

The company is expected to remove spent fuel rods at Daiichi within two years, according to the schedule released today in Tokyo. Engineers will attempt to start removing melted fuel from one of the reactors within 10 years. Decommissioning the units is expected to cost between 1.15 trillion yen and 4 trillion yen. The utility must also find a way to treat and dispose of an estimated 90,000 tons of contaminated seawater that had been used to cool the reactors.

Japanese newspaper The Daily Yomiuri reported today that Japan’s government is considering bringing TEPCO under state control, buying more than two-thirds of the utility’s stock as part of a 2 trillion yen plan that would use funds from the Nuclear Damage Liability Facilitation Fund. TEPCO, a company on the brink of insolvency stemming from surging costs as a result of the disaster, has refuted the report, saying it will work at cutting costs and securing funds.

With Fukushima in cold shutdown, Japan is expected to make a decision on its future energy policy by next spring. Before the disaster, nuclear power made up more than 30% of the country’s power profile, and the country had planned to boost nuclear generation to more than 50% of its supply by 2030.

Sources: POWERnews, TEPCO, The Daily Yomiuri