Safety review sought for Hamaoka 3

17 June 2015

CORRECTED - An earlier version of this article incorrectly gave the expected dates for completion of enhanced safety measures at Hamaoka units 3 and 4 as September 2016 and September 2015, respectively. These dates are in fact September 2017 and September 2016.

Chubu Electric Power Company has requested a safety review by Japan's nuclear regulator of unit 3 at its Hamaoka plant in Shizuoka prefecture. Such a review, a prerequisite for restarting, has already been requested for unit 4 of the plant.

Hamaoka plant - 460 (Chubu)
The Hamaoka plant (Image: Chubu)

The company applied to the Nuclear Regulation Authority (NRA) yesterday for a safety assessment of Hamaoka 3 to verify whether measures taken at the plant meet new safety standards.

Hamaoka 3 - a 1056 MWe boiling water reactor which began operating in 1987 - becomes the 25th Japanese reactor to apply for regulatory approval to restart.

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 had already been permanently shut down.

Chubu enhanced sea defences at Hamaoka, with an 18-metre high tsunami protection wall, 1.6 km in length, completed in December 2012. However, the company later decided to increase the height of this wall to 22 metres after revising its estimate of a potential tsunami height. Other work at the plant 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.

The enhanced safety measures are expected to be completed in September 2016 for unit 4 and in September 2017 for unit 3. Chubu said it is exploring necessary measures for unit 5.

Chubu requested a safety review of Hamaoka 4 in February 2014. However, that review has been delayed by further investigations into a geological fault under the plant. The company said that its own surveys had not found any active fault lines in the area.

Researched and written
by World Nuclear News