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Some of the groundwater flowing from the mountain-side to the sea-side is entering into the nuclear reactor building, causing a continuous increase of contaminated water. This groundwater is pumped up on the mountain side before entering the reactor building so that its flow changes and the groundwater level is lowered. This "Groundwater Bypass System" serves to reduce the amount of contaminated water flowing into the reactor building. The water pumped up on the mountain side is temporarily stored in tanks (Step 1) and analyzed by TEPCO and third party organizations to check "whether values are less than TEPCO's upper concentration limit" (Step 2). Water stored in the tanks is only discharged to the ocean after it has been confirmed that the water quality is less than TEPCO's upper concentration limits (Step 3). (Groundwater exceeding the TEPCO's upper concentration limits is not discharged.)

* TEPCO's upper concentration limits are more stringent than those set by the Reactor Regulation and the WHO guideline for drinking-water quality. TEPCO will discharge the pumped up groundwater into the ocean only after confirming that values are less than those permitted values.

Work Steps from Pumping up to Discharge

  • *1:

    As a countermeasure to prevent airborne radioactive materials from mixing with the groundwater, the openings of the intake pipes of the storage tanks are located inside the control area where there is no possibility of contamination.

  • *2:

    Water quality analysis is regularly conducted by third party organizations.

  • *3:

    TEPCO's upper concentration limits are more stringent than those set by the Reactor Regulation and the WHO guideline for drinking-water quality. TEPCO will discharge the pumped up groundwater into the ocean only after confirming that values are less than those permitted values.

Monitoring Conditions in Groundwater Bypass Operation

Radioactive nuclide analysis of pump wells and temporary storage tanks is carried out on a regular basis. In addition, sampling is performed at the time of water discharge and the radioactive concentration in the premises of the nuclear power station as well as its neighboring areas, including the inner and outer ports, is measured in order to confirm that there is no impact on the ocean.

Frequently Asked Questions

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