Hamaoka - 22 meters anti-tsunami wall

December 21, 2012

Chubu Electric adding 4 meters to breakwater at Hamaoka nuclear plant

http://ajw.asahi.com/article/0311disaster/fukushima/AJ201212210073

THE ASAHI SHIMBUN

Chubu Electric Power Co. will heighten a breakwater to better protect what is considered Japan’s most vulnerable nuclear power plant from a tsunami caused by another major quake off the Pacific coast.

Akihisa Mizuno, president of Chubu Electric, told reporters on Dec. 20 that the 1.6-kilometer-long breakwater to shield the Hamaoka nuclear power plant will rise to 22 meters from the initially planned 18 meters.

The change came after the utility, using government data, estimated that an earthquake in the Nankai Trough in the Pacific Ocean could spawn a tsunami that would inundate the Chubu plant in Omaezaki, Shizuoka Prefecture, southwest of Tokyo.

The move is also apparently aimed to win the approval of local residents and municipalities to restart the plant.

The utility said the total cost to raise the breakwater and for other anti-tsunami measures at the plant will grow to almost 150 billion yen ($1.78 billion). Completion of the breakwater is now expected late next year from the initially planned end of March.

After the tsunami last year led to the meltdowns at the Fukushima No. 1 nuclear power plant, Prime Minister Naoto Kan instructed Chubu Electric to shut down operations at the Hamaoka plant, citing its vulnerability to natural disasters.

In August, a government-sponsored expert panel predicted that a maximum 19-meter-high tsunami could hit the coast of Omaezaki following a Nankai Trough earthquake.

Chubu Electric’s own studies showed that after hitting the planned 18-meter-high breakwater, the tsunami would reach a maximum 21.4 meters and breach a 1-km section of the wall. The flood levels would be 1 to 3 meters around the No. 3 and No. 4 reactor buildings and 1 to 6 meters around the No. 5 reactor building.

The utility said a 22-meter-high wall will be able to block the tsunami.

However, it said seawater in such an event will pour out of intake water ponds, inundating most areas around the No. 3, No. 4 and No. 5 reactor buildings up to 1 meter and flooding some areas up to 2 meters.

To deal with such a situation, the utility will install shields that automatically close at an opening at the No. 5 reactor building.

Hamaoka plant to be protected by 22-meter seawall to counter tsunami

http://mainichi.jp/english/english/newsselect/news/20121221p2g00m0dm006000c.html

NAGOYA (Kyodo) -- Chubu Electric Power Co. said Thursday it has decided to increase the height of a seawall it is building at its Hamaoka nuclear power plant to 22 meters as part of its efforts to counter quake-triggered tsunami.

"We've decided to increase the height of the seawall to prepare for largest-class tsunami," company President Akihisa Mizuno said at a press conference, referring to the decision to make the seawall 4 meters higher than earlier planned.

The seawall at the plant in Shizuoka Prefecture is expected to be capable of blocking 19-meter-high waves the government has estimated to possibly approach if a huge earthquake hits the Tokai region in central Japan, allowing flooding to occur only through water intake chambers.

The cost for the additional construction work will reach several billions of yen. The utility will not change its plan to finish installing tsunami countermeasures by December next year.

Chubu Electric was asked by the government in May last year to suspend operations of all the reactors at the Hamaoka plant until sufficient countermeasures are taken, given it is known to be standing on an assumed epicentral area for a massive earthquake.

The government made the request in the wake of the nuclear crisis at Tokyo Electric Power Co.'s Fukushima Daiichi complex, triggered by the magnitude 9.0 earthquake and ensuing tsunami on March 11 last year.