Wednesday, April 18, 2012

TEPCO: Fukushima Reactor Building Will Not Collapse in Earthquake, Not Leaning

TEPCO simulations say that buildings are strong enough to be shaken again, but does that account for reactor 4 building leaning due to damage? They measured floor which is level, but could it be level AND leaning? 

The Tokyo Electric Power Company, Incorporated, would like to make comments on subjects that are reported by the newspapers, TV or websites.

Reactor buildings will not collapse even if earthquake with the same scale as that of Tohoku - Pacific Ocean Earthquake occurs again.

April 5, 2012
At 11:04 pm on April 1, a 5.9-magnitude earthquake centered in the coast of Fukushima Prefecture occurred. Hama-dori of Fukusihma Prefecture registerd intensity 5 lower on the Japanese seismic (intensity) scale of 7. No abnormalities were detected at facilities for water injection into the reactors, nitrogen gas injection, cooling of spent fuel pool, and the treatment of highly contaminated water at Fukushima Daiichi Nuclear Power Station. They all operate normally after the quake. As for the degree of the shake of the reactor buildings, Unit 6's reactor building's foundation registered 40.7 gal in horizontal direction and 19.4 gal in vertical direction.

We, TEPCO, evaluates earthquake-proof safety by developing Design Basis Earthquake Ground Motion Ss as large-scale quake which would possibly occur in future. For example, the degree of shake of Unit 6's reactor building's foundation against the Design Basis Earthquake Ground Motion is 448 gal in horizontal direction and 415 gal in vertical direction (, which is around 10 times large in horizontal way and around 20 times large in vertical way compared with the quake occurred on April 1, 2012). We assess that the level of this Design Basis Earthquake Ground Motion is almost same as the one recorded for the Tohoku - Pacific Ocean Earthquake. Based on the Motion, we simulated the damaged situation of the current reactor buildings of Unit 1 to 4, having implemented quake response analysis for the reactor buildings as well as equipments and pipes which are important in terms of safety. As a result, we confirmed that there are no negative signal, such as shear/ twist of quake-proof walls of buildings, the fact that the stress of facilities/ piping lowers the standard value, and the fact that buildings collapse and facilities/ piping lose their functions.

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Cooling of Unit 4 spent fuel pool properly accomplished

February 14, 2012
The temperature of the spent fuel pool of Fukushima Daiichi NPS Unit 4 is maintained between 25 - 30 degrees Celsius, and the top of the spent fuels are 7 meters below the water surface of the pool. Due to the earthquake that occurred on January 1, of which the epicenter was near Karasujima, the water level of the skimmer surge tank became temporarily low, but there was no change in the water temperature and the water level of the pool. We put a camera in the pool on February 9 in order to measure the clarity, and we confirmed that, although there is a certain amount of debris due to the explosion of the building, as we have confirmed on May 7 last year, the spent fuels themselves are secured inside the rack.

Furthermore, on January 22, we have inspected the condition of the fifth floor of the reactor building, and we have confirmed that the floor was parallel to the water surface of the reactor well, which indicates that the building is not leaning.

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