Important Report from TEPCO

Approximately 400t of groundwater flows into the station building per day and turns into contaminated water. The groundwater bypass is a measure to decrease the amount of groundwater flowing into the building and control the increase of contaminated water by pumping up and bypassing the groundwater flowed from the mountain side, upstream the building.

Bypassed groundwater is naturally found water.

Bypassed groundwater is naturally found water, and therefore, it is not considered as disposal at sea.

Bypassed groundwater is naturally found water, and therefore, other methods such as evaporation are not considered.

Bypassed water is naturally found water.
For processed contaminated water,
(1) a fundamental measure against groundwater flowing into the reactor building which is the cause of increased water
(2) a measure to improve decontamination capabilities of the contaminated water treatment facility and secure stable operation including alternative facility in an event of failure
(3) a measure to further install ground facilities to manage liquid waste
will be thoroughly implemented, and there will be no simple discharge into the sea.
There will be no discharge into the sea without the approval of persons concerned.

It is managed so that contaminated water will not leak outside the building by keeping the level of groundwater near the building higher than the water level inside the building.

The impact of contaminated water on the environment surrounding the building is assessed by surveying the impact on subdrain and sea near the building.

The groundwater bypass is planned to gradually increase the amount of water pumped up while monitoring the water level, and it is expected to decrease around 100t of water flowing into the building per day at maximum.

Since bypassed groundwater is naturally found water, radiation concentration is at a sufficiently low level even when comparing it to that of the sea and rivers in the periphery.
Pumped up water is stored in a tank first to examine its water quality.

In addition to regularly conducting detailed analysis, a third-party organization will also measure the radioactive materials, and such results will be disclosed on the website.

It was necessary to check the self-shielding effect on the background radiation level in areas where the background radiation level is high like Fukushima Daiichi Nuclear Power Station, but there was not enough attention.

Background count (number of radial rays) of Cs137 at Fukushima Daini Nuclear Power Station was around 100 times smaller than that at Fukushima Daiichi Nuclear Power Station.

(Reference) Background count of Cs137 (when measured for 50,000 seconds)
· Fukushima Daiichi Nuclear Power Station: 10³-10⁴ order
· Fukushima Daini Nuclear Power Station: 10¹-10² order
*Since the count differs according to detector, it is recorded in the order range

Generally, there are different measurement values in the analysis result due to different measuring equipment and background radiation level.

The standard permissible value for water discharge is set at below 1Bq/L (Cs137) based on various regulatory values for public water such as the result of the measurement of public water areas within Fukushima Prefecture by the Ministry of the Environment as well as guides for radioactive materials at bathing areas and reference value of drinking water indicated by the Ministry of Health, Labour and Welfare.

If the standard permissible value (below 1Bq/L for Cs137) cannot be satisfied, water pump-up from wells and discharge into the sea will be stopped.

Currently, the plan up to 800,000t is being examined. Further installation of tanks will be examined according to future conditions of contaminated water.

The current plan is to secure the tank installation location by clearing areas on-site, and there is no plan for off-site installation.
Locations to install tanks for contaminated water are set at an elevation of 35m.

There are approximately 900 units of storage tanks for processed water at Units 1-4.

In regard to steel cylindrical tanks with flanges joined by bolts, out of the contaminated water storage tanks currently installed at Fukushima Daiichi Nuclear Power Station, the service life of the seal used for flange joints where deterioration is likely to advance the most is around 5 years, but it will not necessarily become out of use in 5 years if it is repaired. Therefore, application of repair work (waterproofing technology) from outside is currently being examined as a preventive and protective measure against leakage from the main body flange.
The body of said tanks has sufficient durability, but it can be appropriately used for a long period of time by inspecting and repairing flange joints.

The feasibility of water shielding walls of frozen soil will be examined, but it is believed that it will reduce the amount of groundwater flowing into the building.

It is necessary to reduce the amount of groundwater flowing into the building with the groundwater bypass first.

Survey results showed that leakage from the underground reservoir is minor and that the contaminated area is limited. Spread of contaminated water will continue to be monitored, and it is also planned to collect soil.
Evaluation of migration of contaminated materials into the surroundings accompanying leakage from underground reservoir No.2 estimates that it will take a very long time, approximately 200 years, for the radioactive materials to reach the sea and radiation concentration is below the detectable limit.

The underground reservoir will be investigated for the cause of leakage. Currently, contaminated soil is being removed and remaining water is being diluted to reduce the risk of spread of contamination.
2 layers of high-strength polyethylene sheets are used for the underground reservoir. The method used combines the existing technology to store rainwater and technology of the final waste repository. Tests such as pin hole tests and water filling tests were conducted during the work and after the work was completed.

There is a technology to separate highly concentrated tritium, but since concentration of tritium contained in liquid waste at Fukushima Daiichi Nuclear Power Station is much lower, it is difficult to separate it. However, the technology to remove tritium will continue to be examined including overseas knowledge.

The test (lab test) to improve removal performance, conducted at the hot laboratory at Fukushima Daiichi Nuclear Power Station using test equipment simulating the actual equipment, found that there is potential for improving removal performance by changing the final layer of the adsorbent to activated carbon adsorbent. Therefore, the durability of the added activated carbon adsorbent will be checked (around late July) to ultimately determine the direction of things.