Decommissioning Plan of Fukushima Daiichi Nuclear Power > Plan & Action > Major Initiatives for Water Management > Groundwater Bypass System

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Groundwater Bypass System

The groundwater bypass, one of several strategies being employed to reduce the accumulation of contaminated water at the plant, aims to intercept clean groundwater as it flows downhill toward the sea, and reroute it safely around the facility.

The water's quality is monitored regularly by an independent third party using safety and environmental standards which is significantly more stringent than either the limit set by the government or even the standard for drinking water established by the World Health Organization. Final agreement on the ocean discharge were made with the government, Fukushima Prefecture and the Fukushima fishermen's union.

Since its start of operation on May 21 2014, the groundwater bypass is estimated to have been reducing the amount flowing into the building basements by up to 100 tons per day according to the analysis done in 2014. The bypass will help reduce the volume of water that becomes contaminated and then needs to be cleaned and stored on site.

*The discharge will only be implemented after confirming that the water quality is well within the drinking standard set by the World Health Organization.

  • Landside Impermeable Wall
  • Subdrain
  • Groundwater drain
  • Sea-side impermeable wall
  • Seawater piping trench

Procedures from Pumping up to Discharging

  • *1:As a countermeasure to prevent airborne radioactive materials from mixing with the groundwater, the opening of the intake pipes of the storage tanks is located inside the management area where no possibilities of contamination can be found.
  • *2:Water quality analysis is regularly conducted by third party organizations.
  • *3:The TEPCO's upper limits of radioactive concentrations are more stringent than the ones 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 the radioactive concentrations of the water do not surpass the upper limits.

Monitoring in the operation of groundwater bypass

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

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