Consideration of the first formal application by a nuclear plant operator to restart a suspended reactor under the government’s new stress test system was postponed after experts challenged the safety of the procedure.
Consideration of the first formal application by a nuclear plant operator to restart a suspended reactor under the government’s new stress test system was postponed after experts challenged the safety of the procedure.
Kansai Electric Power Co. was the first utility to submit a first-stage stress test report, on the No. 3 reactor at its Oi nuclear plant in Fukui Prefecture, and had expected the government’s Nuclear and Industrial Safety Agency (NISA) to consider its results on Nov. 14.
But calls from nuclear experts for a review of the safety standards underpinning the whole system forced NISA to put off examination of the report.
"It is incomprehensible to try to reach a conclusion on whether reactors are safe based on the test results without reviewing the safety screening process, which is flawed," Hiromitsu Ino, professor emeritus in metal materials at the University of Tokyo, told the meeting on Nov. 14.
Ino argued that all of the country's reactors should be shut down immediately and should not be restarted until they had passed the second stage of the government’s stress test regime.
The existing system is allowing operators to continue running reactors until they have to suspend them for routine maintenance. For the restart this time, however, they have to submit a report like that submitted for the Oi plant under the first stage of the stress test system. Under the first-stage test, utilities have to assess how much safety cushion their reactors have against quakes and tsunami at expected levels and beyond.
That report must then be passed by NISA and ratified by the Nuclear Safety Commission of Japan, a panel within the Cabinet Office.
The second-stage tests are stricter. They apply to all of Japan’s nuclear plants except the No. 1 and No. 2 nuclear plants in Fukushima Prefecture, but the government is allowing existing plants to keep running while the second-stage analyses are carried out.
The stress tests are based on computer simulations conducted by the operators of nuclear plants.
Koji Okamoto, professor of nuclear engineering at the University of Tokyo, joined Ino in questioning the logic of the system at the hearing.
"The second-stage test designed to determine if the nation's nuclear plants are intrinsically safe should be conducted first," he said.
Masashi Goto, a part-time lecturer at Shibaura Institute of Technology who worked on nuclear reactor design when working with Toshiba Corp., also raised questions about the limited focus of the testing regime on natural disasters such as quakes and tsunami.
He said the system should also be looking at the ability to withstand aircraft accidents, beached vessels, terrorist attacks, fire and other risks.
A suggestion from Ino that local residents should be allowed to sit on panels of specialists looking at the safety of plants was rejected by NISA, which said meetings to explain decisions to local residents would be held instead.
On the same day as the suspended meeting, Shikoku Electric Power Co. submitted a report on the safety of the No. 3 reactor at its Ikata nuclear plant in Ehime Prefecture.
According to the utility, acceleration of seismic motion of 1,060 gal, or 1.86 times the expected maximum in the area of the plant would not damage nuclear fuel in the reactor. It said the reactor would also withstand a 14.2 meter tsunami, 4.07 times the size of the maximum predicted there.
The company also said that it would be able to significantly extend the length of time the reactor could be cooled in the event of a blackout from the current five hours to 10.7 days through the use of emergency equipment.