Sea Area Monitoring Results | Tokyo Electric Power Company Holdings, Incorporated

Disclosure of monitoring results

In accordance with the government's basic policy on ALPS treated water we have strengthened monitoring of seawater (outside of the harbor), fish, and seaweed (specimen sampling commenced on April 20, 2022) in order to continually check of the dispersion of primarily tritium in seawater and the status of marine organisms. Monitoring results are being disclosed on our website.

No significant change has been detected. (as of month day, year)

Indices of Significant Changes Please click here for details of indices

Click any of the monitoring points on the map to view a graph of the monitoring results

=Fukushima Daiichi Nuclear Power Station

=Discharge outlet

Seawater monitoring points

Click here for analysis results for quick tritium measurements
Quick measurements are intended to ascertain ocean conditions more rapidly by raising the detection limit and obtaining analysis results quicker.

Fish/seaweed monitoring points

Click here for more detailed analysis results

Click here for the graph (Only in Japanese)

Click here for Overarching Radiation monitoring data Browsing System around Japan (ORBS)

The Overarching Radiation monitoring data Browsing System around Japan is a website that gathers sea area monitoring measurements taken from various locations that have been disclosed by TEPCO as well as related ministries/agencies and local governments, etc., and displays them on a map format for easy viewing thereby providing objective and comprehensive data on sea conditions.

Click here for information on how to use ORBS

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ALPS Treated Water, etc. Conditions

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Tritium
Cesium 137
Cesium 134

World Health Organization (WHO) standard limit for drinking water (10,000Bq/Liter)

Discharge Suspension Level*3（700Bq/L）

Investigation Level※4（350Bq/L）

Discharge Suspension Level*2（30Bq/L）

Investigation Level※3（20Bq/L）

Past data

World Health Organization (WHO) standard limit for drinking water (10Bq/Liter)

Past data

World Health Organization (WHO) standard limit for drinking water (10Bq/Liter)

Past data

Unit that indicates how much radiation a radioactive substance can emit
Past data indicates the maximum and minimum values for one year. The observed range is included in the results of normal analysis and detailed analysis.
ND (Not Detected) indicates that concentrations were below detectable limits.
Detectable limits vary depending on the measurement environment and the measurement device.
Minuscule amounts of radioactive substances are periodically measured by lowering detection limits.
According to completion of the installation of the ALPS treated water dilution/discharge facility and the dredging construction in Unit 5/6 intake open channel, the monitoring point "in front of Unit 6 intake" has been changed to "in front of Unit 5 intake" since July 3, 2023.
To ensure the safety of the seawater sampling work, the sampling point has been temporarily changed to a point approximately 1,300 meters south from the south water discharge outlet of the Fukushima Daiichi Nuclear Power Station Units 1-4 since June 11, 2024.

Unit that indicates how much radiation a radioactive substance can emit
Past data indicates the maximum and minimum values for one year. The observed range is included in the results of normal analysis and detailed analysis. Measurement points that do not show past values had not been sampled from prior to FY2021.
ND (Not Detected) indicates that concentrations were below detectable limits.
Detectable limits vary depending on the measurement environment and the measurement device.
Tissue free water tritium refers to tritium that exists as water in the tissues of an animal.
Organically bound tritium refers to tritium that is bound to organic material, such as proteins, etc., and exists in the tissues of an animal.
Seawater (surface) values represent measurement results from the previous day.
The graph shows the highest detection value obtained by analyzing multiple fish samples collected at the same location on the same day.
If all samples are below detectable limits, the highest detection limit is shown. For more information, please click here.

Unit that indicates how much radiation a radioactive substance can emit
Past data indicates the maximum and minimum values for one year. The observed range is included in the results of normal analysis and detailed analysis. No values are shown for seaweed since it is sampled only once a year.
ND (Not Detected) indicates that concentrations were below detectable limits.
Detectable limits vary depending on the measurement environment and the measurement device.
Tissue free water tritium refers to tritium that exists as water in the tissues of an animal.
Organically bound tritium refers to tritium that is bound to organic material, such as proteins, etc., and exists in the tissues of an animal.
Seawater (surface) values represent measurement results from the previous day.

Positioning of index (discharge suspension level)

In ALPS treated water will be discharged into the sea after dilution with seawater, the surrounding sea area has been monitored to ensure that the water to be discharged is dispersing sufficiently. Index, as discharge suspension level, has been set in order to determine if the discharge needs to be suspended as the facility operation in the event that sea area monitoring results indicate that the water to be discharged is not dispersing sufficiently (tritium concentration unusual situation).
If the aforementioned set values are exceeded, the sea discharge will be immediately suspended.
In order to quickly ascertain the tritium concentration conditions in the sea area, the detectable limits at 14 locations will be raised to 10 Bq/L, and measurements will be taken.

Setting index (discharge suspension level)

① In the vicinity of the discharge outlet (10 locations within 3km of the power station) : 700 Bq/L

Although the government's policy stipulates the upper limit of tritium concentration during the discharge at less than 1,500 Bq/L, the maximum management value during the discharge has been set approx. 700 Bq/L, which will not be exceeded 1,500 Bq/L even in consideration of facility and measurement uncertainties and also this value is included in the implementation plan.
Based on this maximum management value, the index (discharge suspension level) for this area in the vicinity of the discharge outlet (within 3km from the power station) has been set at 700 Bq/L.

② Outside the vicinity of the discharge outlet (4 locations within a 10km square in front of the power station) : 30 Bq/L

The index (discharge suspension level) for this area outside the vicinity of the discharge outlet (10km square in front of the power station) has been set at 30 Bq/L, which is 1.5 times of 20 Bq/L, as the case which the maximum tritium concentration* in the sea area in front of nuclear power stations throughout Japan over the last three years (20 Bq/L) clearly exceeds is considered to be an unusual situation.

【Reference】The legal requirement 60,000 Bq/L
The WHO’s drinking water guidelines 10,000 Bq/L