Dismantling work to start at Hamaoka units

Japan's nuclear regulator has given the go-ahead to Chubu Electric Power Company to start removing "peripheral" equipment from units 1 and 2 of its Hamaoka nuclear power plant in Shizuoka prefecture. Both units were permanently shut down in January 2009.

Japan's nuclear regulator has given the go-ahead to Chubu Electric Power Company to start removing "peripheral" equipment from units 1 and 2 of its Hamaoka nuclear power plant in Shizuoka prefecture. Both units were permanently shut down in January 2009.

The five-unit Hamaoka plant (Image: Chubu)

The utility submitted a decommissioning plan for Hamaoka 1 and 2 in June 2009, which was subsequently revised in September of that year. The overall plan divided the decommissioning of the two units into four stages. The first stage is for preparations for dismantling work at the units, while the second stage covers the dismantling and removal of equipment surrounding the reactors. The third stage is for the dismantling of the reactors themselves, while the fourth covers the demolition of buildings at both units.

The plan was approved by the ministry of economy, trade and industry in November 2009, when Chubu began stage 1 of the decommissioning program. The company completed that stage in March last year and it then applied to the Nuclear Regulation Authority (NRA) for approval for stage 2 to begin.

Chubu announced today that the NRA has now given approval for stage 2 to start. During this stage, the company will begin the dismantling of equipment surrounding the reactors - including the exhaust stacks, steam piping, the turbines and the main condensers - and will continue to conduct contamination surveys and decontamination of the reactor pressure vessels. This stage is scheduled to be completed in 2022.

The utility said it will recycle dismantled components generated during stage 2 as much as possible. Radioactive wastes will be stored safely within the buildings of Hamaoka 1 and 2 until a disposal method is determined, it said.

Chubu expects to complete the decommissioning of Hamaoka 1 and 2 by 2036.

Hamaoka 1 and 2 are both boiling water reactors, starting up in 1973 and 1978, respectively. Unit 1 had a capacity of 540 MWe while unit 2's capacity was 840 MWe. Chubu decided to close both units in January 2009 as they required expensive modifications to meet seismic standards imposed after the July 2007 Niigata Chuetsu offshore earthquake.

Following the accident at Fukushima Daiichi, Chubu agreed in May 2011 to comply with a request from then-prime minister Naoto Kan that Hamaoka units 4 and 5 were shut down and unit 3, which was already offline for regular inspections, was not restarted until sea defences had been bolstered. The enhanced safety measures are expected to be completed in September 2016 for unit 4 and in September 2017 for unit 3. Chubu is exploring necessary measures for unit 5.

Researched and written
by World Nuclear News