Japan’s Tohoku Electric Power Co has announced plans to decommission unit 1 at its Onagawa nuclear plant in Miyagi Prefecture, which began operation in 1984.
The company cited difficulties in taking additional safety measures as well as the relatively small output of the 524MWe boiling water reactor (BWR) that made it unprofitable. Tohoku Electric President Hiroya Harada said: “We took into consideration technical restrictions associated with additional safety measures, output and the years in use.”
Onagawa 1 faces a problem due to the restricted space within its containment vessel, which complicates installation of additional safety equipment, such as fire extinguishing equipment, power supply equipment and alternative water injection pumps.
Tohoku will seek approval from the Ministry of Economy, Trade and Industry to decommission Onagawa 1 and will draw up a decommissioning plan for submission to the Nuclear Regulation Authority (NRA). Onagawa 1 is the tenth operable Japanese reactor to be declared for decommissioning since the Fukushima Daiichi accident.
The Onagawa nuclear plant, which was the closest plant to the epicentre of the March 2011 earthquake, comprises three units, the other two being larger 825MWe BWRs, which began operating in 1995 and 2002. The earthquake damaged four of the five external power lines, but there was sufficient power for all three reactors to be brought to cold shutdown. Onagawa 1 briefly suffered a fire in the non-nuclear turbine building and the basement floors of Onagawa 2 were flooded. The company is building a 29-metre-high sea wall to guard the complex.
In 2013, Tohoku applied to the NRA for safety assessments of Onagawa 2 to verify whether measures taken at the plant meet new safety standards, although the utility does not plan to restart the unit before fiscal year 2020. Construction of the additional safety measures ar expected to be completed before March 2019. Tohoku is also preparing documents for NRA inspections for Onagawa 3.
Map: Current status of Japanese reactor license approvals, based on information from JNSI
