It was reported that a powerful earthquake of 6.8 magnitude on July 16, 2007 at the Kashiwazaki-Kariwa facility run by Tokyo Electric, Japan caused tipping over of about 100 barrels of low-level nuclear waste at waste storage building of a nuclear power plant. Some of the barrels were found with the lids open. The earthquake also caused some contaminated water from the Tokyo Electric's plant to escape into the sea.
Water which is thought to be from the spent fuel storage pool spread on the operation floors 3 and 3M of the reactor building (non-controlled zone) of unit #6. It was recognized that some leaked water was discharged into sea through draining route. Discharged water activity (after dilution) is reported to be fully less than legislative criteria (0.2Bq/cm^3). It is claimed the discharging had already stopped.
Radionuclides such as I-131, I-133, I-135, Cr-51 and Co-60 were detected on July 17, 2007 in the main ventilation duct (Unit # 7). The ventilation ducts were found bent at the connections to the main stack. The total amount of radioactivity (release?) was estimated to be 3x10^8 Bq. The main stack radiation monitors (units # 1to 6) and monitoring posts in the power station has shown no significant indication of radiation.
Just after the earthquake on July 16th, fire broke out in the unit #3 house transformer that supplies electricity to the reactor facility. It was extinguished at 11:58 AM. The regulator requested licensee to review its fire protection and preparedness system.
The four operating reactors at Kashiwazaki-Kariwa were shut automatically after the earthquake, and the other three had already been halted for routine maintenance, Tokyo Electric said on its Web site. The plant is 9 kilometers (5.6 miles) from the epicenter of the quake. The trade ministry and Kashiwazaki town authorities ordered Tokyo Electric to keep the seven nuclear reactors idle pending safety checks. The government criticized the company for being slow to disclose the radioactive leaks.
The Kashiwazaki-Kariwa plant was not designed to withstand an earthquake as powerful as the magnitude 6.8 tremor. The Trade ministry last year updated regulations to make the nation's nuclear power stations more earthquake resistant. Japan has 55 reactors that generate about one-third of the country's power, making the nation the third-largest nuclear producer in the world. Tokyo Electric operates 17 reactors.
On July 19, Shares of Tokyo Electric Power Co. dropped to a nine-month low on concern that the company's nuclear facility in central Japan, the world's biggest, may be shut for a year after the earthquake caused radioactive leaks.
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