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Thursday, April 7, 2011
Overcoming the nuclear crisis
The crisis at Tokyo Electric Power Co.'s Fukushima No. 1 nuclear power plant does not warrant optimism. Nuclear fuel in the cores of the No. 1, No. 2 and No. 3 reactors is believed to have been severely damaged. In the No. 4 reactor's storage, where spent nuclear fuel is kept, water evaporated at one point, and a hydrogen explosion released radioactive substances into the environment.
The government should pay close attention to proposals made by 16 Japanese experts on nuclear power engineering, nuclear physics and radiology on April 1. It should mobilize all available means to mitigate the crisis.
Tepco is cooling the reactors by pumping water into them by using pumps connected with external power sources. But it cannot stop highly radioactive water from flowing out of the reactors. The more water it pumps into the reactors, the more contaminated water flows outside. Apparently, components for containing radioactive water have been damaged. The No. 2 reactor's suppression pool is feared to have cracked.
On land, the accumulated radiation level during 11 days from March 23 has reached 10.34 millisieverts in the town of Namie, Fukushima Prefecture, just outside the 30-km radius of Fukushima No. 1. Residents inside the zone should evacuate or stay indoors. If the accumulated level over several days reaches a range of 10 to 50 millisieverts, the government calls on residents to stay inside their homes to avoid radiation.
The situation at Fukushima No. 1 is "extremely serious" and demands Japan's all-out efforts, the 16 experts said in their April 1 statement. Three of the 16 — Mr. Shiori Ishino, professor emeritus at the University of Tokyo, Mr. Shunichi Tanaka, former acting chairman of the Atomic Energy Commission, and Mr. Shojiro Matsuura, former chairman of the Nuclear Safety Commission — explained the statement at the education and science ministry.
Since those who signed the statement include former members of the AEC, a body that sets the nation's basic policy for development and use of nuclear power, the NSC, a body that sets the nation's basic nuclear safety policy, and scientists belonging to the Atomic Energy Society of Japan, the government and Tepco should share their sense of crisis and humbly follow their proposals.
The 16 "as people who have pushed peaceful use of nuclear power" expressed their regret over the nuclear crisis and apologized to people. But they did not hide their fear that a critical situation may develop at Fukushima No. 1. They do not rule out the possibility that as time goes on, a molten core melts a weak part of a pressure vessel and enters a containment vessel, destroying the reactor's function to contain radioactive substances, or that hydrogen gas forming inside a pressure vessel explodes and destroys a containment vessel, causing serious radioactive contamination over a large expanse of land and sea. They warn that release of a large amount of radioactive substances could make uninhabitable not only the current evacuation zone but also larger areas.
Mr. Tanaka and others said that the current makeshift efforts to cool the No. 1, 2 and 3 reactors will not be able to completely cool down molten nuclear fuel so as it will not burst through the bottom of pressure vessels. They also said the three reactors contain a much larger amount of radioactive substances than the Chernobyl nuclear plant did.
The points made by the statement include: (1) utmost efforts must be made to both prevent the release of a large amount of radioactive substances and to reactivate the residual heat removal system which internally circulates water to cool reactors and spent fuel storages, (2) spent nuclear fuel must be completely immersed in water, (3) detailed measurement of radioactivity both in the air and the soil in various areas and assessment of their effects must be announced so that area-specific measures can be taken and (4) residents should be fully informed before and after radioactive substances are vented from reactors.
It adds that since hydrogen is forming all the time in the reactors, hydrogen explosions must be prevented at any cost.
The statement also calls for (1)increasing personnel at Fukushima No. 1 to lower their exposure to radiation and to enable them to take enough rest and (2) setting up the headquarters for the crisis containing operations inside or near the plant site (so that headquarters personnel share the burden of radiation exposure and pain with on-site workers.)
The 16 experts say it is essential to set up a system in which the NSC will take the lead in strategically and flexibly utilizing the knowledge and experience of Japan's nuclear authorities — including the Japan Atomic Energy Agency and the National Institute of Radiological Sciences — the power and related industries and universities to end the nuclear crisis. Prime Minister Naoto Kan must exercise strong leadership in setting up this system as soon as possible.