While reviews of initial stress test results for Japanese reactors are progressing, it could still be several months before the first restart approval comes. The shutdown of unit 2 of the Ikata nuclear power plant for a periodic inspection means that only five of the country's 54 power reactors are now in operation.
|The Ikata plant (Image: Shikoku)
Shikoku Electric Power Co shut down the unit - a 566 MWe pressurized water reactor - on 13 January for refuelling and a mandatory periodic inspection. According to its schedule, the company expects the inspection to be completed on 12 April, but, like all other Japanese nuclear plants, it is not yet known when the unit will be permitted to restart.
With the shutdown of Ikata 2, just five of the country's 54 power reactors are in operation, according to data released by the Japan Atomic Industry Forum. Thirty two units are not operating as they have been shut for periodic inspection and have not been allowed to restart. A further 17 units, representing 15,990 MWe of capacity have been shut down due to the tsunami or at the government's request.
Following the accident at the Fukushima Daiichi plant in March 2011, the Japanese government said that all reactors would be subjected to stress tests to be conducted in two phases before approval for restart could be given. Step one will be applied to those reactors which have been taken offline for periodic inspections to determine whether they could withstand large earthquakes and tsunamis. Under this step, utilities are required to examine the safety margin of important pieces of equipment in accordance with guidelines set by the country's Nuclear and Industrial Safety Agency (NISA) and Nuclear Safety Commission (NSC). Based on the results of these initial tests, the government is to decide whether a reactor shut for inspections can or cannot resume operation.
Step two of the tests will involve a comprehensive safety assessment of all reactors and will be conducted to enhance the reliability of regular safety checks. These tests will be similar to the stress tests co-ordinated by the European Commission.
Although the initial step of the stress tests has been completed at some reactors, no decision has yet been made on restarting any units. According to Reuters, NISA is preparing a report on its findings based on tests run by Kansai Electric Power Co on units 3 and 4 of its Ohi plant to present to a government-appointed panel that will review the results and issue approvals. "We're organising data and findings from the past discussions of stress test reports, aiming to discuss mainly the No.3 and No.4 Ohi reactors on 18 January," a NISA official was quoted as saying. He added that the panel could request further information before approving NISA's recommendations. The panel's approval would lead to a further review by the NSC, the prime minister and relevant cabinet ministers.
In addition to government approval to restart, utilities must also get permission from local authorities. However, public opposition to reactor restarts remains high in some areas. If no reactor restart approvals are given, all of Japan's units could be out of operation by the middle of this year.
Researched and written
by World Nuclear News