Hamaoka 4 seeks restart approval

14 February 2014

Chubu Electric Power Company has requested a safety review by Japan's nuclear regulator of unit 4 at its Hamaoka plant in Shizuoka prefecture. It becomes the seventeenth Japanese reactor to seek permission to restart.

The company applied to the Nuclear Regulation Authority (NRA) today for a safety assessment of Hamaoka 4 to verify whether measures taken at the plant meet new safety standards.

Hamaoka NPP 400 (NRA)
Chubu's Hamaoka plant (Image: NRA)

In May 2011, two months after a massive earthquake and tsunami triggered the accident at the Fukushima Daiichi plant, then-prime minister Naoto Kan personally decided that the Hamaoka plant would have to shut until it had bolstered sea defences. Kan said that analysis from earthquake experts under the Ministry of Education predicted an 87% chance of a magnitude 8 earthquake in the region within 30 years and the risk of a major tsunami.

Chubu complied with Kan's request, shutting down Hamaoka units 4 and 5, and not restarting unit 3 which was already offline for regular inspections. Units 1 and 2 have already been permanently shut down.

Chubu has finished implementing enhanced sea defences at Hamaoka, with an 18-metre high tsunami protection wall, 1.6 km in length, completed in December 2012. Other work included flood-proofing of key buildings and extensive measures to enhance emergency reactor cooling functions.

Further measures are being taken in response to revised regulations introduced by the NRA in July 2013, which must be met before plants can secure regulatory permission to restart. These include reinforcement of supports for pipes and cable-related equipment plus ground reinforcements at various points around the site to enhance earthquake resistance. Steps are being taken to protect outdoor seawater pumps and pipes, while protection against fire, floods and tsunamis and numerous other emergency measures is being further enhanced. Chubu is also increasing the height of the tsunami protection wall to 22 metres. This work is expected to be completed by the end of September 2015.

Hamaoka 4 - a 1092 MWe boiling water reactor - becomes the seventeenth Japanese reactor to apply for regulatory approval to restart.

NRA chairman Shunichi Tanaka was cited by the Asahi Shimbun newspaper as saying that none of the assessments are expected to be completed before April.

Researched and written
by World Nuclear News