To reduce the risk of radioactive materials in contaminated water, water is first treated with cesium/strontium filtering equipment to remove most of the contamination.
It is then treated in a multi-nuclide removal facility (ALPS), thereby removing most of the remaining radioactive materials except for tritium.

Treatment of Contaminated Water

Note on “Water treated with multi-nuclide removal equipment, etc.” is notated. (revised in March, 2020)

  • Treated water for which the sum of concentration ratios required by law, with the exception of tritium, is less than 1 is notated as either, “water treated with multi-nuclide removal equipment, etc.” or “treated water”.
  • Treated water that has not been completely treated is notated as, “water treated with multi-nuclide removal equipment, etc. (for which the sum of concentration ratios required by law equals or exceeds 1)”.
  • When referring to both of the aforementioned types of treated water collectively, the notation, “treated water*” is used.

※ Treatment of high concentration contaminated water containing strontium (reverse osmosis concentrated saltwater) generated at the time of the accident was completed in 2015.

See the Treated Water Portal Site for data and other information about treated water* (contaminated water after treatment).

For more information on the treatment and storage of waste generated by ALPS, please see, “Plan for the Stabilization and Treatment of Waste generated by Contaminated Water Purification and Treatment Facilities”.

What Is Tritium?

  • Tritium is also known as hydrogen-3 or 3H, as its nucleus has two neutrons in addition to the proton of ordinary hydrogen. It is similar in nature to hydrogen. Existing mainly as water, it is found not only in the natural world and in tap water but also in our bodies. While it is slightly radioactive as a low-energy beta emitter, the weakness of the energy means it can be blocked by a single sheet of paper. Even though it enters the body through daily activities such as drinking tap water, it is discharged by means of metabolism without being stored or becoming concentrated in the body.

Status of Tank Storage

  • Water that has been treated with cesium/strontium filtering equipment and in ALPS is stored in tanks on site. Currently there are 1,083 such tanks on site in which approximately 1.33 million tons of water is being stored. To reduce the risk of leakage, flange tanks used initially after the accident were completely replaced with more reliable welded tanks. Moreover, measures have been taken to prevent water from flowing outside the tank area, such as constructing double dikes around the tanks, etc., should any leaks occur.

Handling of Treated Water*

The basic policy on what to do with the water for which treatment with ALPS and other facilities has been completed, will be determined by the government based on discussions in government committees that consider technical and social aspects, and upon coordinating with, and obtaining the understanding of, local communities and other concerned parties. While safely managing these tanks, TEPCO will proceed prudently and appropriately while listening to the opinions of the parties concerned and considering government policy.

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