IAEA reports on Japan's stress tests

The International Atomic Energy Agency (IAEA) has published its final report on Japan's revised nuclear safety assessment process. It found that the new Japanese measures are "generally consistent" with IAEA safety standards, but outlined several areas for improvement.

A mission to Japan that was acrried out between 23 to 31 January saw a team of ten experts from the IAEA and its member states spend time with Japan's nuclear safety regulator, the Nuclear and Industrial Safety Agency (NISA). The IAEA team was sent at the request of the Japanese government.

"The Three Mile Island and Chernobyl accidents brought about an overall strengthening of the safety system. It is already apparent that the Fukushima accident will have a similar effect."

Richard Meserve, Carnegie Institution for Science

NISA is conducting a two-stage assessment on all of Japan's nuclear plants to ensure they have adequate protection against extreme external events. The country's nuclear power companies must report on the safety margins of their power plants under Fukushima-like accident conditions in a 'primary assessment.' These documents are to be reviewed by NISA before a reactor can be granted permission to restart at the end of a mandatory inspection outage. The 'secondary assessment' will be an overall evaluation that relates closely to the stress tests carried out in the European Union and elsewhere.

During their trip, the mission also visited Kansai Electric Power Company's Ohi plant for an overview of how Japan's compliance with nuclear safety monitoring - known as the Comprehensive Safety Assessment - is being implemented by nuclear operators.

The team released a preliminary report of their findings to the Japanese government at the end of their visit. That said NISA and nuclear operators had "promptly addressed" emergency safety measures after the accident at Fukushima Daiichi.

The mission's final report has now been delivered to Japanese officials by the IAEA. In it, the team highlight good practices and also identify improvements that could enhance the overall effectiveness of Japan's Comprehensive Safety Assessment process and further regulatory activities. Among its recommendations, the team stated that NISA should eventually require plant operators to develop comprehensive accident management programs in compliance with recently issued IAEA safety standards in the area of severe accident management.

The mission also noted that all plant upgrades aimed at increasing the safety margins against earthquake and tsunami hazards should be studied by the relevant local authorities and checked against the relevant IAEA safety standards.

James Lyons, director of the IAEA's nuclear installation safety division and leader of the mission, said: "This mission report provides additional information regarding the team's recommendations and overall finding that NISA's instructions to power plants and its review process for the Comprehensive Safety Assessments are generally consistent with IAEA safety standards." Lyons commented, "I hope nuclear regulators around the world use this report as a tool to evaluate their own safety assessment processes." He added, "We must learn the lessons of the Fukushima Daiichi accident so we can prevent a repeat of those terrible events a year ago."

All but one of Japan's nuclear power reactors are now idle and no date has yet been slated for the first reactor restart.

Learning lessons

At a meeting last week at the IAEA's headquarters in Vienna, over 230 international nuclear safety experts from 44 IAEA member states and other international organizations discussed technical aspects of reactor and used fuel safety in light of the Fukusihima accident and what lessons are being learned from the it.

Richard Meserve, chairman of the International Nuclear Safety Group and president of the Carnegie Institution for Science, said: "The Three Mile Island and Chernobyl accidents brought about an overall strengthening of the safety system. It is already apparent that the Fukushima accident will have a similar effect."

He told the meeting that the IAEA and its member states had made a "comprehensive, thoughtful and quite impressive" effort to analyze the Fukushima accident and to take appropriate actions to respond. Meserve said that both regulators and operators in member states are "taking aggressive actions to increase safety." While noting that member states' analyses were independent and used different approaches to study various aspects of the accident, the recommended actions to be taken were fairly consistent. "I take confidence from the fact that these similarities suggest that significant issues have not been overlooked," he said.

Researched and written
by World Nuclear News