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Fukushima Daiichi NPS Prompt Report 2015



No environmental or health effects seen as measurements of radioactivity in seawater near Fukushima Daiichi remain steady

FUKUSHIMA, Japan, April 23, 2015 -Full power has been restored to drainage water pumps at Fukushima Daiichi Nuclear Power Station (NPS) that had been affected by the failure of a generator that powers them at 11:48, April 22 Japan time. The generator was replaced with a new one that day.

Although the temporary outage of the pumps caused some water to flow from the drainage channel into the sea, measurements of seawater both inside and outside the port area of the plant show no increase in radioactivity. The incident posed no additional exposure risk to workers or the surrounding communities.

Pumps Help Manage Rainwater

At the Fukushima Daiichi NPS, rainwater is managed through the use of various drainage channels. Up to eight pumps are used to pump drainage water out of Drainage Channel "K" into Channel "C", to prevent the water (which can pick up contaminants inside the facility) from flowing directly to the ocean. Ordinarily, only one or two pumps are needed, but totally up to eight pumps are prepared as needed to handle the water increase when it rains.

The pumps are inspected three times a day to ensure they are working properly, and during a routine inspection at 8:45 on April 21 workers discovered the pumps had stopped, the result of the failure of the generator that powered them. A backup generator was activated that day, powering up to two pumps, more than sufficient to manage current water loads. The cause of the breakdown is currently being determined.

Because the precise time of the generator outage cannot be determined, it is not known exactly how much drainage water may have flowed into the ocean. However, water monitoring shows no impact on water quality in the ocean:

Sampling results at "South water outlet" (ocean water taken near "K" Drainage discharge point) are:

As of April 21
Cs-134: ND (Not detected, Detection limit: 1.1 Bq/L)
Cs-137: ND (Detection limit: 1.3 Bq/L)
Gross beta: ND (Detection limit: 15 Bq/L)

As of April 22
Cs-134: ND (Detection limit: 1.3 Bq/L)
Cs-137: ND (Detection limit: 1.3 Bq/L)
Gross beta: ND (Detection limit: 15 Bq/L)

<Reference> Regulation limits and WHO drinkable level
Regulation limits
Cs-134: 60 Bq/L
Cs-137: 90 Bq/L
Sr-90: 30 Bq/L
H-3: 60,000 Bq/L

WHO drinkable level
Cs-134: 10 Bq/L
Cs-137: 10 Bq/L
Sr-90: 10 Bq/L
H-3: 10,000 Bq/L
The pumping arrangement is a temporary measure until "K" Drainage will be reconfigured so that it flows into the sea within the plant's port area, like "C" Drainage, rather than outside it.
For detail information such as location of the drainages please go to:

Although no health or environmental impact is believed to have resulted from the temporary outage, TEPCO remains committed to working with governments, and international organizations to monitor ocean radioactivity, promptly and accurately report results.
For further information regarding monitoring results, please visit:


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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