A catastrophic meltdown of nuclear fuel in reactors at the Hamaoka nuclear power plant would take place if a blackout and failure of emergency power sources lasting three days crippled the cooling system, according to operator Chubu Electric Power Co.
The utility also said in a report released Jan. 19 that storage pools for spent nuclear fuel at its plant in Omaezaki, Shizuoka Prefecture, would melt in 25 days under similar circumstances.
The scenarios were drawn up in response to a request by the Shizuoka prefectural government, which sought the information to prepare for nuclear contingency drills scheduled for next month.
The plant, which has five reactors, has been shut down since May.
Naoto Kan, prime minister at the time, ordered the closure following the disaster at the Fukushima No. 1 nuclear power plant triggered by the March 11 Great East Japan Earthquake and tsunami.
Kan cited vulnerability of the facility, given that it sits in the presumed hypocentral area of a huge quake that is expected to strike the Tokai region within 30 years.
The plant, which went into operation in the 1970s, has long been regarded as a potential time bomb.
The plant’s No. 1 and No. 2 reactors are in the process of being decommissioned.
According to Chubu Electric, 6,625 spent fuel rods are stored at the plant.
The utility arrived at its figures after calculating how long it would take for cooling water in reactors and storage pools to evaporate based on the amount of heat generated by the nuclear fuel.
The Hamaoka plant is equipped with emergency power sources and a cooling system that uses seawater and other means to cool reactors and spent fuel storage pools.
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