Stress test results in for Ikata 3

14 November 2011

Shikoku Electric Power Co has submitted the results of the first part of the two-step stress tests for unit 3 of its Ikata nuclear power plant in Ehime prefecture. It is the second Japanese utility to submit a stress test result.


Ikata (Shikoku) 
The three-unit Ikata plant (Image: Shikoku Electric)

In July, the Japanese government said that Japanese reactors would be subjected to stress tests to be conducted in two phases. 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 will decide whether a reactor shut for inspections can or cannot resume operation.


Step two 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 proposed by the European Union.


Kansai Electric Power Company (Kepco) was the first utility to submit results of the first stage stress test. On 28 October it submitted a report to NISA,  and authorities in Fukui prefecture and Ohi town giving the results of the initial step of these stress tests at Ohi 3.


Shikoku Electric said that the results submitted today show that there are sufficient safety margins in the design basis of significant facilities and equipment for the unit to survive large earthquakes and tsunamis. It added that urgent countermeasures had been made at the plant following the Fukushima Daiichi accident, but it would strive to further enhance safety measures at the unit.


According to Shikoku, Ikata 3 - an 846 MWe pressurized water reactor - would be able to withstand an earthquake with ground acceleration of up to 1060 gal (1.8 times its design basis of 570 gal) and a tsunami 14.2 metres in height (four times its design basis). In addition, should the unit lose all off-site power supply, the reactor could still be kept cool for up to almost 11 days through the use of fire engines pumping water, while the used fuel pool could be cooled for just over 8 days.


NISA will now examine the results and then pass them on to the NSC for consideration. The decision to allow Ohi 3 will then be taken by Prime Minister Yoshihiko Noda; minister for the economy, trade and industry Yukio Edano; minister for conclusion of the nuclear disaster Goshi Hosono; and chief cabinet secretary Osamu Fujimura.


As of 2 November, just 11 of Japan's 54 power reactors were in operation, according to data released by the Japan Atomic Industry Forum. This represents 9864 MWe, or 20%, of the country's total nuclear generating capacity of 48,960 MWe. Thirty units, with a combined generating capacity of 26,383 MWe are not operating as they have been shut for periodic inspection.


Researched and written

by World Nuclear News