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Fukushima Daiichi NPS Prompt Report 2015


Correction and apology: In the prompt report dated February 24 and titled "Recent Topics: TEPCO investigating cause of brief water incident at Fukushima,"please delete the third paragraph ..."Ordinarily, TEPCO requires that any water discharged into the sea have "gross beta" levels below 5 becquerels per liter." The requirement for "gross beta" level below 5 becquerels per liter only applies to groundwater bypass discharge. We apologise for the confusion caused.

No workers believed exposed in brief rise in radioactivity in drain water

FUKUSHIMA, February 24, 2015-The Tokyo Electric Power Company is investigating the cause of a brief rise in the radioactivity of drainage water on Sunday and will make its findings public.

No workers are believed to have been exposed when measurements of the "gross beta" nuclides (total amount of nuclides that emit beta rays such as Strontium90) rose from below 1,500 to between 5,050 and 7,230 becquerels per liter of water. Although some of the water is believed to have reached the sea, measurements of radioactivity in the port area adjacent to the plant did not show any significant increase. The company also patrolled each tank facility and confirmed no leakage. Recent water radioactivity measurements are posted at

TEPCO will increase the frequency of some ocean water sampling from once a week to daily during the investigation period.

Plant operators were automatically alerted to the increase in radioactivity by sensors designed for that purpose. The air radiation dose monitored in the vicinity of drainage route at the time of the alarm did not show any significant changes. After confirming that the measurement results of the water pumped up from the drainage has returned to normal, TEPCO resumed drainage operations.

The company is investigating the potential causes of the event and will report its findings promptly.

For the location of the drainage and related materials, please go to


Tokyo Electric Power Company, Inc. (TEPCO) is Japan's largest power company, supplying energy to the greater Kanto area, including Japan's two most populous cities, Tokyo and Yokohama. Its 34,000 employees are committed to providing safe, reliable power to its 29.0 million customers, diversifying energy resources to ensure sustainability, and contributing to economic growth while fully meeting its responsibilities after the Fukushima Daiichi accident.
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