Editor's Note: John Boyd is an IEEE Spectrum contributor reporting from Kawasaki, Japan.This is part of IEEE Spectrum's ongoing coverage of Japan's earthquake and nuclear emergency. For more details on how Fukushima Dai-1's nuclear reactors work and what has gone wrong so far, see our explainer.
Over the past week, workers have made grudging progress towards stabilizing Japan's Fukushima Dai-1 nuclear power plant. Yet a dramatic announcement today, in which Japanese prime minister Naoto Kan called for a new energy policy, suggests that the country may turn away from nuclear energy.
First, the grudging progress: Just a few days after air-filtering equipment began cleaning the radioactive air inside the damaged No. 1 reactor building, workers and government safety officials were able to enter the building early Monday morning to carry out a survey of conditions inside.
"We are making great progress there, so that workers are now able to enter the building," said Goshi Hosono, a senior aid to prime minister Kan, at a briefing for the foreign press on the afternoon of Monday, May 10. "Our next goal is to confirm that the situation there is safe and workable, and then to restore the (reactor) cooling system as soon as possible."
Such confirmation will be no easy matter. Tokyo Electric Power Co. (TEPCO) reported the same day that radiation levels in the building ranged from 10 millisieverts per hour to as high as 700 millisieverts per hour on the second level of the building. The latter figure is almost three times the 250-millisieverts maximum level workers are allowed to be exposed to in one year.
A TEPCO official told the press that the company had "hoped the radiation level would go down to 1 millisievert per hour," but that was nowhere near the case. To allow workers to operate safely, the company may bring in lead shielding or might focus on removing highly radioactive debris, the result of the hydrogen explosion that damaged the building following the 11 March earthquake. The TEPCO official voiced concern that the continued high radiation levels could force a change in the company's plans. But despite the hazardous conditions, workers entered the building again to adjust the reactor’s measuring gauges in preparation for flooding the pressure vessel, which is done to cool the crippled reactor.
According to TEPCO's stabilization and clean-up plan, the company will aim to bring the plant to a cold shutdown in less than nine months. To achieve that goal, TEPCO first has to deal with the near 70 000 tons of radioactive water that has accumulated in the turbine basements and outside trenches associated with reactors 1, 2, and 3. The pooled water near reactor No. 2 has been designated highly radioactive.
“Until we are able to remove this highly radiated water (in the Unit 2 trench) we will not be able to proceed with any other work,” said Hosono.
Currently, the water is being transferred to a central waste-water treatment facility on the site to await decontamination. TEPCO is working towards decontaminating the water in cooperation with French nuclear supplier Areva and Kurion, a nuclear waste management company in the United States. Areva’s technology is based on a co-precipitation method that injects chemical reagents into the water to isolate elements such as radioactive iodine and cesium, which are then separated by precipitation for removal. Kurion then uses a vitrification process that turns the radioactive materials into a compacted glass to facilitate storage.
Hidehiko Nishiyama, the deputy director-general of the Nuclear and Industrial Safety Agency, participated in the press briefing with Hosono. He explained that the decontamination system will be used in conjunction with Japanese desalination equipment. "Once the contaminated water has gone through the systems and has been cleaned, it will be separated into two kinds of water, one of which will be stored in a tank, and one which will be recirculated (for cooling) the reactor." The water decontamination is expected to begin in June.
While the situation at Fukushima Dai-1 seems to be slowly improving, the general outlook for nuclear power in Japan got worse this week.
In a major development, Chubu Electric Power Co. agreed on Monday May 10 to suspend operation of its Hamaoka nuclear power plant in Shizuoka prefecture, about 200 kilometers southwest of Tokyo, "until further measures to prevent tsunami are completed." The decision came after Prime Minister Kan's May 6 request that the power company cease all operations at the plant, citing concerns over its safety. Kan said the government had predicted that there's an 87 percent chance that a magnitude 8 earthquake will strike the region within the next 30 years.
The coastal Hamaoka plant is located near a major fault line in central Honshu, Japan’s largest island. Reactors No. 4 and No. 5 are currently operating and the company had planned to restart the No. 3 reactor, currently offline for inspection, in July. Reactors No. 1 and No. 2 were shut down in January 2009 and are set to be decommissioned.
Although the plant is protected by sand dunes between 10 and 15 meters high, the company plans to build a concrete seawall to further protect against tsunami. Construction is expected to take two three years, according to press reports. The gross capacity of the three active reactors is about 3.5 gigawatts and accounts for roughly 10 percent of the region’s power supply. The company had been providing TEPCO with make-up power, but will now have to suspend that service, as it scrambles to meet its own region’s demands.
On Tuesday, May 11 Prime Minister Kan took another dramatic step, announcing that Japan would seek a new national energy policy that puts an increased emphasis on renewable energy and conservation. "We need to start from scratch," Kan said in a press conference. "We need to make nuclear energy safer and do more to promote renewable energy."
Kan's announcement suggests that the government will drop an energy policy released last year, which called for the construction of 14 more nuclear reactors before 2030; that plan called for nuclear to supply 50 percent of the country's energy needs.