A fire at a nuclear power plant in Niigata Prefecture after Monday's earthquake was likely caused by land subsidence, exposing yet another danger in the anti-temblor design of the facility, officials said.
     A bridge column supporting a transformer and electric cables sank into the ground, causing an electrically-charged copper bar to make contact with covering metal, according to Niigata prefectural government officials. The contact could have caused a short-circuit or overheating.
     The officials also said the fire-fighting system at the Kashiwazaki-Kariwa Nuclear Power Plant may have been damaged by the land sinkage, possibly preventing plant workers from extinguishing the fire by themselves. The local fire department had to douse the fire.
     The latest finding raised the possibility that even a small fire could lead to unexpected damage at a nuclear plant if the fire-fighting system is inadequate or disabled in an earthquake.
     The Niigata prefectural government has conducted on-site inspections based on a safety agreement with Tokyo Electric Power Co., operator of the plant.
     Under government guidelines, buildings that house nuclear reactors and turbines must be constructed on solid ground.
     But auxiliary facilities, such as transformers, are not required to have a quake-resistance strength equivalent to that of the primary structures. That is because ensuring safety of reactors is given the highest priority in the event of an earthquake, rather than repairing damage or taking fire-fighting measures for auxiliary facilities such as transformers.
     According to prefectural government officials, the soil around the No. 3 reactor building was removed when it was built directly on bedrock. The soil was returned after the building was erected.
     The bridge column, which stands on the soft ground around the reactor building, sank into the ground during Monday's quake.
     Seismometers installed at the plant registered a shaking at least twice as strong as the level that the plant was designed to withstand.
     The bridge column supports the transformer and power cables, which transmit electricity generated inside the reactor building to the transformer.
     The prefectural officials said a copper belt that conducts electricity and the metal covering the belt, both inside the transformer, might have come in contact when the cables were tilted.
     That may have led to a short-circuit that generated sparks causing the fire. Another possibility is that the metal became so overheated that oil inside the transformer ignited.
     The officials also said a water pipe connected to a hydrant might have been damaged under the weight of the bridge column that sank into the ground.
     The pipe was located under the bridge column, and the officials said the damage possibly crippled fire-fighting activities by plant workers in the early stages.(IHT/Asahi: July 19,2007)

     Tokyo Electric Power Co. said Thursday that data was lost from 63 seismometers at the Kashiwazaki-Kariwa nuclear power plant in Niigata Prefecture following the Niigata Prefecture Chuetsu Offshore Earthquake that hit the facility Monday.
     The company also said air containing radioactive substances was emitted from one of the reactors for two days.
     These new revelations came after TEPCO was found to have committed various errors in its initial efforts to deal with problems arising from the effects of Monday's earthquake. Among 97 seismometers at the power plant, TEPCO lost parts of data from 63 older types of seismometers, the company said.
     The seismometers were supposed to constantly transmit data to Tokyo over phone lines, but the lines became overwhelmed immediately after the quake, and data were overwritten with a series of aftershocks before the previous transmissions were completed, it said. Up to 1-1/2 hours of data were lost from some of the devices.
     Although data from 30 newer seismometers were transmitted during the initial quake, the loss of the other raw data may impact the investigation of the quake resistance security check, observers said.
     Meanwhile, TEPCO said Thursday radioactive iodine had been emitted for two days until noon Wednesday from an exhaust fan at the plant's No. 7 reactor.
     After the plant stopped reactor operations, it failed to stop the fan on the turbine that generates electric power, and air containing radioactive substances was emitted from the turbine area, the company said.
     There were no filters to eliminate radioactive substances in the pathway that connects the fan and the exhaust pipe, it said.
     But the amount of the radiation was small and there is no danger to the environment or the residents in the area, it added.
     The power plant stopped the fan on Wednesday, but it will not be known until Friday if the emission of the radioactive iodine was fully stopped.
     TEPCO said it did not detect radiation around the plant, but the government said it will keep a closer watch on the facility.
     The company also confirmed that water leaked again from a damaged part of an fire-extinguishing duct. The total number of problems and instances of damages has so far increased to 63, TEPCO said.
     The Nuclear Safety Commission and the Nuclear and Industrial Safety Agency, an organization under the Economy, Trade and Industry Ministry, said Thursday they found the government's preparedness against disasters and preventive measures insufficient after the officials investigated the plant.
     They said the plant's failure to learn from mistakes at other plants was a problem.
Hokuriku Electric Power Co. had a similar problem at its Shika nuclear power plant when a temblor hit the Noto Peninsula in Ishikawa Prefecture in March.

     Chief Cabinet Secretary Yasuhisa Shiozaki told Vice Economy, Trade and Industry Minister Takao Kitabata on Thursday to ensure electric power companies complete checking safety levels at the nation's nuclear power plants ahead of schedule, government officials said.
     The Nuclear and Industrial Safety Agency revised the seismic resistance guideline for nuclear plants in September and requested electric power companies use the new guideline to check their safety levels by the end of December 2007.
     The government, however, decided to push up safety checks and take immediate preventive measures in the wake of Monday's earthquake.
     "We want [electric companies] to check [their levels of safety] as soon as possible," Shiozaki said during a press conference.