Chubu Electric Power Co. will likely need to take additional steps to safeguard its Hamaoka nuclear power plant after an expert panel warned that towering tsunami could strike the area.
Chubu Electric Power Co. will likely need to take additional steps to safeguard its Hamaoka nuclear power plant after an expert panel warned that towering tsunami could strike the area.
A government study team now says 21-meter tsunami could swamp the plant if a major offshore earthquake occurs.
The plant, at the request by the central government, shut down all its reactors last May.
Chubu Electric must now grapple with the prediction that higher tsunami than anticipated could batter the coastline.
The utility is currently constructing a breakwater that will be 18 meters high when it is completed. The work is scheduled to finish by December.
Although much of the foundation work is in place, Chubu Electric may need to rethink the project to deal with higher tsunami.
The nuclear plant lies in the center of an assumed ground zero region for a Tokai earthquake.
Chubu Electric has already carried out reinforcement work for the No. 3 to No. 5 reactors, which it plans to continue operating.
At the same time, the assumed height of a tsunami that could strike from a combination of Tokai, Tonankai and Nankai quakes was set at only 8 meters.
The company had assumed that a dune levee of 10 to 15 meters in height along the coastline in front of the facility would be sufficient to protect the plant.
However, after the government requested the halt of operations at the Hamaoka plant, Chubu Electric reviewed its safety measures, taking into account that tsunami as high as 15 meters pounded the Fukushima No. 1 nuclear power plant on March 11, 2011, triggering a disaster.
The company decided to construct a breakwater 18 meters high and 2 meters thick and stretching 1.6 kilometers around the plant ground and encircling the No. 1 to No. 5 reactors. The structure was to be a combination of steel, steel frames and steel-reinforced concrete.
Construction began last November. Work to pound in an underground wall of steel-reinforced concrete to depths of 15 to 40 meters until hitting bedrock has been completed at 94 of the 219 planned locations.
Other steps have been taken to prevent water from flooding the reactors if the breakwater is breached. Double-layered doors will be installed for the nuclear reactor buildings and air intake and exhaust openings have been positioned at higher locations.
A floodwall of 1.5 meters has been installed around the seawater intake pump that will be needed to cool the reactor cores.
Chubu Electric officials said the measures are costing the utility 140 billion yen ($1.7 billion).
After the March 31 announcement of a higher tsunami estimate, Chubu Electric said the safety of the Hamaoka plant could be secured even if water flooded the plant grounds.
However, at an April 2 news conference, Yoshinori Moriyama , deputy director-general for nuclear accident measures at the Nuclear and Industrial Safety Agency, said the government basically was seeking assurances that no seawater will ever inundate the plant.
But Moriyama, noting that construction of the breakwater is proceeding, said, that should not be taken to mean that all possible steps are being taken.
"If any new knowledge emerges ... we will ask that new measures be taken," he said.
A high-ranking Chubu Electric executive said, "There will be no change in our policy of implementing a total package of measures."