Trade and industry minister Banri Kaieda on July 6 said that all of Japan’s nuclear power plants must undergo “stress tests” that comprehensively evaluate their safety. The same day, Prime Minister Naoto Kan told the Diet that he had instructed officials concerned to work out new rules for verifying the safety of nuclear power plants, indicating that the results of stress tests will be the basis on judging on whether nuclear power plants now out of operation should be restarted. On Monday, the government said that in the first round, safety-related components of reactors that are going through regular checks but are ready for operation will be tested, and that in the second round, all reactors in operation will undergo comprehensive safety tests.

On June 18, Mr. Kaieda declared that the nation’s operators of nuclear power plants had taken adequate measures to handle severe accidents and called for restarting power plants that are not operating. Currently, 35 of Japan’s 54 nuclear power plants are out of operation due to regular checks or accidents.

The call for stress tests by the government is tantamount to denial of Mr. Kaieda’s June 18 declaration. It proves that the declaration was a political gimmick designed to hasten the restart of nuclear power plants to prevent power shortages in summer. It also betrays that the government is not confident about the safety of nuclear power plants at this stage.

In a stress test, a computer will be used to gauge to what extent nuclear power plants can withstand heavy stress such as the total loss of electrical power. The crisis at Tokyo Electric Power Co.’s Fukushima No. 1 nuclear power plant has prompted the European Union to start stress tests on its nuclear power plants in June.

The government’s new stance has caused confusion among several regional leaders in their decisions related to nuclear power plants. Mayor Hideo Kishimoto of the town of Genkai, Saga Prefecture, who had approved the restart of the Nos. 2 and 3 reactors at Kyushu Electric Power Co.’s Genkai nuclear power station following Mr. Kaieda’s June 18 declaration, withdrew his approval on July 7. The same day, Gov. Yasushi Furukawa of Saga Prefecture said that he would postpone his final decision on the restart of the reactors.

Mr. Kaieda’s safety declaration on June 18 and his sudden call for stress tests on July 6 point to confusion within the government over its policy toward nuclear power. Even so, the requirement of stress tests on all nuclear power plants is a step forward in ensuring the safety of the installations. Stress tests should not be used as a means of justifying the restart of nuclear power stations. They should be used to accurately asses the safety of such facilities. It will be important for people to closely monitor whether stress tests will be properly carried out. The government on its part should realize that its confusion is due to the fact that it has not yet committed itself to a phase-out of nuclear power generation, although this is a difficult path requiring changes in industrial structure and people’s lifestyle.

It is noteworthy that opinions were divided in the government over the stress tests. On July 7, Shinichi Kuroki, councilor of the Nuclear and Industrial Safety Agency under the wing of Mr. Kaieda’s ministry, told a special committee of the Ehime prefectural assembly that he “did not think that the safety (of a nuclear power plant) cannot be confirmed if a stress test is not carried out.” The special committee was deliberating on the issue of the restart of the No. 3 reactor at Shikoku Electric Power Co.’s Ikata nuclear power plant. (The company on July 8 postponed the restart).

In the case of the EU’s stress tests, it is expected to take three and a half months for regulatory authorities to issue an interim report and seven months to issue a final report. If stress tests are conducted in Japan, it is feared that the period in which nuclear power plants will remain out of operation will be prolonged, thus causing power shortages not only in summer but also in winter (from December 2011 to February 2012). But all the parties concerned should realize the harsh reality that as the nuclear crisis at Fukushima No. 1 continues, people will not easily accept the restart of nuclear power plants unless they are fully assured of the plants’ safety. The scenario in the EU’s stress tests envisages a loss of all power sources due to such causes as earthquakes, tsunami and floods. Whether a reactor and a pool storing spent nuclear fuel can be adequately cooled will be ascertained. Whether adequate measures have been taken to prevent the spread of nuclear substances into the environment will also be checked.

In Japan, NISA will decide on the scenario and the methods to be used in a stress test. The Nuclear Safety Commission told NISA that such a test should clearly show that if power sources are lost due to tsunami and other causes, at what point the emergency core cooling system (ECCS) and other safety measures would lose their functions, and at what point a severe accident would occur, such as a meltdown. It also said that such a test should show to what extent substitute measures, such as using a fire engine, can cool a reactor core in case the ECCS is knocked out.

Since NISA is under a ministry that has been pushing nuclear power generation, the type of stress test it will develop must be strictly observed. NISA should make public all the content and the results of the tests.

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