Chubu Electric Power Company has outlined a $1.3 billion plan to increase protection of its Hamaoka nuclear power plant against tsunami and flooding. Countermeasures will include the construction of an 18-metre-high seawall, waterproofing of the diesel generator rooms as well as installation of emergency AC power on higher ground.
In May, Japan’s prime minister, Naoto Kan asked Chubu electric to shut down the Hamaoka plant until upgrades had been carried out. He cited research from the Headquarters for Earthquake Research Promotion that indicates there is an 87% probability of a Magnitude 8 earthquake hitting the Tokai region within 30 years. Days later, Chubu shut down units 3, 4 and 5 of Hamaoka NPS; units 1 and 2 were already permanently closed.
Chubu’s plans include the construction of a 1.6 kilometre-long breakwater wall, reaching 18 meters above sea level. (The wave that flooded the Fukushima Daiichi site reached 15 metres.) The wall will be in addition to 10-15 meter-high sand dunes, which currently protect the plant. Chubu said that the height of the virtual tsunami is about 10 metres above sea level, which does not exceed the natural embankment of the dunes. However, the company said that it would take appropriate measures based on the knowledge from the Fukushima accident and studies from the Central of Disaster Management Council.
In addition to the seawall, general measures will be taken to mitigate flooding inside the plant. These include: the construction of a 1.5-metre-high wall around the seawater pump as well as the reinforcement of watertight doors and the installation of a drain pump to prevent flooding in the equipment room.
Specific measures to protect against prolonged station blackout (SBO) include; strengthening of the grid connection; installation of an emergency generator on a backyard hill, which would not be affected by tsunami and placing a standby generator for disaster management on the roof of the building. A warehouse will be built on high-ground to store emergency equipment and spare parts. In addition, heavy equipment such as bulldozers will be kept on site in case of emergency.
These upgrades are due to be implemented by December 2012, Chubu says.
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