“Contaminated water” refers to water that contains highly concentrated radioactive substances that has been generated as a result of the Fukushima Daiichi Nuclear Power Station accident.
Inside the reactor buildings of Fukushima Daiichi Nuclear Power Station Units 1~3, there is fuel that melted and solidified during the accident (fuel debris). This fuel debris is being kept cool by continuously spraying it with water, but when this water comes in contact with the fuel debris it is exposed to the highly concentrated radioactive substances and becomes “contaminated water”. This “contaminated water” that contains highly concentrated radioactive substances accumulates inside the reactor buildings and when it mixes with groundwater or rainwater flowing into the buildings even more “contaminated water” is produced.
This “contaminated water” is being purified to reduce the concentrations of radioactive substances using multiple types of equipment. After risk has been sufficiently reduced in this manner, it is stored in tanks on site as “ALPS treated water, etc.”.

Click here for information on contaminated water countermeasures

“Contaminated water” and “ALPS treated water” are completely different. The water being discharged into the sea is “ALPS treated water that has been diluted with a large volume of seawater”. It is NOT “contaminated water”.
At the Fukushima Daiichi Nuclear Power Station, water has been continually injected into the reactors since March 2011 in order to cool fuel debris that was produced during the accident. As this coolant water comes in contact with fuel debris, it becomes contaminated with high concentrations of radioactive substances and becomes “contaminated water”. This “contaminated water” is generated on a daily basis as a result.
Furthermore, since this “contaminated water” that contains high concentrations of radioactive substances gradually accumulates inside the reactor buildings, any groundwater or rainwater that finds its way into the reactor building also becomes contaminated.
Therefore, we use several types of purification equipment, such as multi-nuclide removal equipment that we refer to as “ALPS”, to reduce the concentrations of radioactive substances present in this “contaminated water”.
Through ALPS treatment, the concentrations of radioactive substances, excluding tritium, are reduced to levels that fall well below ICRP^* recommendations for discharge into the environment, and Japan’s regulatory standards, and the resulting purified water is referred to as “ALPS treated water”.
Therefore the TEPCO makes a clear differentiation between “contaminated water” and “ALPS treated water”.

*The International Commission on Radiological Protection (ICRP) was established in 1982 as an international organization for giving recommendations on radiological protection from an expert point of view. ICRP recommendations serve as the foundation for laws and regulations all over the world.

There are Japanese laws that stipulate the standards for the discharge of radioactive substances into the environment from a nuclear facility, and there are approximately 1,000 radioactive substances that are covered.
Multi-nuclide removal equipment (ALPS) has been designed to reduce the concentrations of 62 radioactive substances (excluding tritium) that are present in the “contaminated water” that accumulates in the reactor buildings and have been targeted for removal in order to reduce the risk that they pose to people and the environment in consideration of decay as of 2012, to levels that fulfill Government’s regulatory standards for discharge into the environment. The equipment employs treatment methods that take advantage of the chemical and physical attributes of radioactive substances, such as chemically-induced precipitation and filtration through various types of adsorbents.
Recent operation performance has shown that only one treatment with ALPS can reduce the concentrations of radioactive substances to below Government’s regulatory standards that were stipulated in accordance with ICRP recommendations.
The following graph shows a comparison of the concentrations of some of the 62 radionuclides found in “contaminated water” that are present at relatively high concentrations compared to “regulatory concentration limit” that have been measured at the inlet before the purification with ALPS, and at the outlet after purification.

If you look at the concentrations after treatment, you can see that the concentrations have been reduced to below Government’s regulatory standards (regulatory concentration limits) for discharge into the environment.
As for the radioactive substances other than the 62 nuclides and tritium, such as carbon-14, their concentrations have been evaluated as well below the standards.

Approximately 70%^* of the water being stored in tanks has concentrations of radioactive substances other than tritium that exceed the Government’s regulatory standards for discharge into the environment. This water is referred to as “Treated water to be re-purified”. (* As of August 2023. Most recent data can be found here)
When multi-nuclide removal equipment (ALPS) was initially put into operation, priority was given to removing the majority of radioactive substances while purifying as much water as possible so as to reduce radiation levels on site, rather than purifying the water to the point where it meets the Government’s regulatory standards for discharge into the environment. As a result, radioactive substances other than tritium remain at levels that exceed the Government’s regulatory standards for discharge into the environment.
ALPS is capable of reducing the concentrations of radioactive substances other than tritium in the “contaminated water” to levels that meet the Government’s regulatory standards for discharge into the environment, and since 2019, ALPS has been operated with the objective of purifying “contaminated water” so that these standards are met.
We have confirmed that through re-purification with ALPS, the concentrations of radioactive substances, excluding tritium, in “treated water to be re-purified” that exceed the Government’s regulatory standards for discharge into the environment are being reduced to levels that meet these standards, and prior to the discharge into the sea, this water is purified repeatedly if necessary to ensure that discharge standards are met.

Approximately 70%^*1 of the water being stored in tanks has concentrations of radioactive substances other than tritium that exceed the Government’s regulatory standards for discharge into the environment. However, these radioactive substances can be removed to levels well below the Government’s regulatory standards through re-purification (secondary treatment) with multi-nuclide removal equipment (ALPS). Secondary treatment tests that we have performed have proven that the water can be purified without any problems.
(*1 As of August 2023. Click here to see the most recent data).

[Reference] Water is re-purified (secondary treatment) with ALPS to ensure that the sum of the ratios of the concentration of each radionuclide to the regulatory concentration limit*2, excluding tritium, falls below 1.

*2 The sum of the ratios of the concentrations to the regulatory concentration limits, calculated for each radioactive substances.

In 2020, we conducted performance confirmation tests for secondary treatment. During the tests approximately 1,000m³ of water was taken from two tank groups (approximately 2,000m³ in total) for which the sum of the ratios of the concentration of each radionuclide to the regulatory concentration limit differ (J1-C Group and J1-G Group) and subjected to secondary treatment, and we confirmed that it was possible to reduce the concentrations of radioactive substances (62 types of radioactive substances + Carbon-14), excluding tritium, to below Government’s regulatory standards (sum of the ratios of the concentration of each radionuclide to the regulatory concentration limit: 1). Furthermore, a third-party analysis of ALPS treated water subjected to secondary treatment with ALPS yielded the same results as TEPCO's analysis.
[Sum of the ratios of the concentration of each radionuclide to the regulatory concentration limit of 62 radionuclides targeted for removal (62 radionuclides) + Carbon-14)]^*3
J1-C Group: [Prior to treatment] 2,406→ [After treatment] 0.35
J1-G Group: [Prior to treatment] 387→ [After treatment] 0.22

*3 For calculation purposes the detection limit was used for those radioactive substances for which concentrations were below detection limits.
Of the radionuclides targeted for removal (62 radionuclides) + carbon-14, 12 types of radioactive substances were detected (Strontium-90, Yttrium-90, Ruthenium-106, Rhodium-106, Antimony-125, Tellurium-125m, Iodine-129, Cesium-135, Cesium-137, Barium-137m, Cobalt-60, Carbon-14).

The Japanese Government’s Subcommittee on Handling of the ALPS Treated Water (hereinafter referred to as the “ALPS Subcommittee” (November 2016 - February 2020)) and the Tritiated Water Task Force (December 2013 - June 2016) performed technical evaluations of five methods of disposal (“geosphere injection”, “underground burial (concrete solidification)”, “discharge into the sea”, “vapor release” and “hydrogen release”).
In the case of “geosphere injection”, for example, which is a method by which ALPS treated water is injected into gaps in the geosphere layer and sealed, suitable geosphere layers (storage layer) are necessary and it is unknown whether suitable geosphere layers exist beneath or near the Fukushima Daiichi Nuclear Power Station site. If no suitable geosphere layer is found, geosphere injection cannot be carried out. Also, during meetings of the Government’s Task Force, the opinion was raised that "methods for long-term monitoring of the injected water have not been established, thereby making it difficult to confirm safety." It was also brought up that new regulations and standards related to disposal concentrations would have to be determined, which would be problematic.
In the case of "underground burial", ALPS treated water is mixed with a cement-based solidifying agent and poured into a concrete pit for burial underground. In the report from the ALPS Subcommittee, it is noted that ① solidification involves heat and thus will evaporate the tritium present in the water, and ② therefore the establishment of new regulations may be necessary, not to mention that a suitable disposal site would need to be found.

As we proceed with the decommissioning work to reduce risks, such as fuel removal from the spent fuel pools of Unit 1 and 2, and fuel debris (melted fuel that solidified as it cooled down) retrieval at Unit 1, 2, and 3, it is essential to secure the space on site for the construction of facilities to safely storage retrieved fuel debris, etc.*, including the space where tanks as already located.
Long-term on-site storage has been discussed by the Japanese Government’s “Subcommittee on Handling of the ALPS Treated Water (ALPS Subcommittee)”. ALPS Subcommittee concluded that “additional space for installing more tanks than currently planned is limited”, as a result of having assessed the efforts of expanding the capacity of existing tanks and improving the efficiency of placement of tanks. For storage in expending the of tanks, there are issues that are “ the marginal gain of capacity relative to surface area is limited, because longer period would be needed for installation and leak inspection, and also in the event of damage, the amount of leakage would be very large”. They concluded that “there was no merit to installing larger tanks in Fukushima Daiichi Nuclear power Station.”
The handling of ALPS treated water is part of the decommissioning work of the Fukushima Daiichi Nuclear Power Station, and is indispensable for completing decommissioning and enabling recovery in the region.
*Examples of facilities that will be needed to move safely and steadily forward with decommissioning:
　- Spent fuel storage facility
　- Storage management and training facility for fuel debris retrieval
　- Fuel debris and radioactive waste storage/analysis facility

TEPCO’s basic policy is to ensure that measures for decommissioning, contaminated water and treated water, etc. being implemented at the Fukushima Daiichi Nuclear Power Station are accomplished within the premises of the Fukushima Daiichi Nuclear Power Station.
To fulfill our responsibility of safely and steadily implementing decommissioning and contaminated water countermeasures as an implementing body, in accordance with our fundamental principle of "balancing recovery with decommissioning," we consider that storing of ALPS treated water off the premises is undesirable, as it would expand the area with risks and impose additional burden on the regional communities.
The report from the Japanese Government’s “Subcommittee on Handling of the ALPS Treated Water (ALPS Subcommittee)” states that, "The decommissioning and contaminated water management are part of continuous risk reduction efforts, and as such, it is fundamental to proceed with the decommissioning works within the existing site area, as removing radioactive materials and placing them outside of the site area might entail increased risk."
After years of discussion by the ALPS Subcommittee, the Government’s Basic Policy on handling of ALPS treated water at the Fukushima Daiichi Nuclear Power Station (discharge into the sea) was announced in 2021.

Tritium is normal hydrogen with two extra neutrons (hydrogen-3) and its chemical properties are very similar to normal hydrogen. It mostly bonds with oxygen and exists in the form of water.
Due to the instability of its atomic nucleus, one of the neutrons emits an electron and transforms into a proton. As a result, it becomes helium. The electron emitted during this process constitutes a type of radiation known as beta ray.

There are various types of radiation, including alpha rays, beta rays, gamma rays, and X-rays. The ability of these radiations to penetrate matter varies according to their type.
In the case of tritium, while it only emits beta rays, their energy is so weak that even a single sheet of paper can block them.

Tritium is continuously produced in the natural environment when cosmic rays from space (cosmic radiation) interact with the atmosphere. The amount produced naturally is 4,500 times the annual discharge limit from the Fukushima Daiichi Nuclear Power Station (22 trillion Bq). And, it is important to note that tritium is discharged into the oceans and atmosphere on a daily basis from nuclear facilities all over the world as part of normal operations. As a result of this natural production in the environment, tritium replaces hydrogen and combines with oxygen to form water and is present all around us, such as in water vapor in the atmosphere, rainwater, and the oceans. Rainwater, seawater and drinking water throughout Japan contain tritium in concentrations ranging from 0.1 to several becquerels per liter. Through the consumption of drinking water^* etc., several tens of becquerels of tritium is always present in our bodies.

* The World Health Organization (WHO)’s guidelines for drinking-water quality specifies a concentration index for tritium in drinking water at 10,000 becquerels per liter.

Tritium is a relative of hydrogen and bonds with oxygen to form water molecules (HTO) that contains tritium.
Since the chemical attributes of water molecules (H2O) and water molecules that contain tritium (HTO) are almost identical, it is extremely difficult to remove tritium from water.
Although technology for separating tritium from tritiated water does exist, it is a technology targeted the water that contains extremely high concentrations of tritium (more than 10,000 times the concentration of tritium in ALPS treated water). At current time, no technology was close to practical use for ALPS treated water. (Same view has been expressed by the Japanese Government’s Subcommittee on Handling of the ALPS Treated Water (ALPS Subcommittee) and the IAEA).
We will continue to closely watch new trends pertaining to technology for separating tritium, in order to thoroughly address this issue in accordance with the government’s Basic Policy that was announced in April 2021.

Since the energy of the radiation (beta ray) emitted by tritium is extremely weak and cannot be directly measured, so special analysis methods are required for measuring tritium concentrations. The methods also differ depending on detection levels for the concentrations of tritium in the specimens to be analyzed, so it can take anywhere from several days to approximately one month to obtain measurement results from sample specimens. We refer to this method as “normal (precision) measurement.” However, if we want to obtain analysis results quickly, we can raise the concentration detection limit and perform measurements in less time, as a “quick measurement.”
For liquid samples like water, before taking measurements, it’s essential to eliminate the effects of radiation from other radioactive substances and prevent attenuation caused by suspended particulate matter in the water. This is achieved by distillation. Furthermore, a reagent (scintillator) that emits light when irradiated is added to impurity-free distilled water and the mixture is left to stand in the dark for a full day among other necessary pre-treatments. Furthermore, when measuring samples with very low tritium concentrations, an electrolytic concentration process is added to increase the tritium concentration in the distilled water.
In addition to the tritium contained in the water in their bodies (free water tritium: FWT), fish and seaweed also contain organically-bound tritium (OBT). For the analysis of organically-bound tritium (OBT), after freeze-drying the sample, the dried sample needs to be combusted to collect the moisture in the combustion gases. This process requires even more specialized preparatory steps than that for liquid samples, like seawater, or the water-based tritium (FWT) in fish and seaweed. Depending on the condition of the sample and the concentration detection level, the analysis can take anywhere from at least 1.5 weeks to up to a month.
It's worth noting that the concentration of water-based tritium (FWT) in fish and seaweed is generally believed to be approximately the same* as the tritium concentration in the seawater from the collection site. Therefore, based on the analysis results of seawater, it's believed that the impact on fish and seaweed can be detected early.

* Tritium is barely concentrated when taken up by aquatic life in its water state and is quickly excreted, so the concentration factor in aquatic life is considered to be “almost 1”.

The government’s regulatory standard for tritium in the water to be discharged into the environment (60,000 becquerels per liter) is based on the concentration that, if someone were to drink approximately 2 liters of the water discharged from a nuclear facility's discharge outlet every day for 70 years, they would receive a radiation dose of 1 millisievert for a year.
[Reference] The average annual radiation dose received from natural background radiation in Japan is approximately 2.1 millisieverts.

The regulatory standard for tritium varies by government. This difference is due to the varying approaches taken by countries when determining these values.
For instance, the World Health Organization (WHO)’s standard (10,000 becquerels per liter) is a reference for determining the need for radiological protection measures for drinking water so that annual exposure dose is 0.1mSv. On the other hand, the EU standard (100 becquerels per liter) is also for drinking water and is set as a screening value to decide if further investigation is necessary.
In Japan, there are no standards for tritium in drinking water or food. Instead, the government has set a regulatory standard for the tritium concentration when it's discharged into the environment, ensuring its safety.

[Reference] Regulatory standards for tritium in water across various country (tritium concentration limits for drinking water)

The Government’s Basic Policy states that the tritium concentration to be the same as that in operational target (less than 1,500 Bq/liter) for the currently implemented discharge of water from the groundwater bypass and subdrains in Fukushima Daiichi Nuclear Power Station, not only to strictly comply with the regulatory standard for discharge into the environment but also to dispel concerns of consumers as much as possible.
In order to achieve this standard, the ALPS treated water must be sufficiently diluted (more than 100 times) by sea water. In conjunction with dilution, the concentrations of radioactive substances other than tritium are also greatly diluted^*.

*By diluting ALPS treated water more than100 times, the post-dilution sum of the ratios of concentration of each radionuclide to the regulatory concentration limit other than tritium is less than 0.01. Furthermore, even with the inclusion of ratio of concentration of tritium, the value would still be less than 0.035.

According to the Japanese Government’s Basic Policy on handling of ALPS treated water (announced in April 2021), the annual amount of tritium to be discharged will be less than 22 trillion Bq/year, which was the maximum amount discharged^* by the Fukushima Daiichi Nuclear Power Station prior to the 2011 nuclear accident. This amount is within the scope of precedent for the discharge of tritium from nuclear power stations within Japan and overseas.
In accordance with this Basic Policy, TEPCO has set the maximum annual tritium discharge amount at 22 trillion Bq, and will discharge tritium water in amounts that will prevent this maximum amount from being exceeded. The most recent data at the end of each fiscal year shall be used to revise tritium discharge plans so that the annual amount discharged falls below 22 trillion Bq.
Furthermore, all countries that have nuclear power facilities, including China and Korea, discharge tritium on a daily basis. For example, in 2019, approximately 91 trillion Bq of tritium water (liquid waste) was discharged from the Wolseong Nuclear Power Plant in Korea, and in the same year approximately 124 trillion Bq of tritium water (liquid waste) was discharged from the Qinshan Nuclear Power Plant #3 in China. Despite this however, no impact attributable to tritium was seen in either of these countries.

* Value set for each nuclear power station that serves as a reference for tritium discharged during normal operation.

The discharge of ALPS treated water into the sea shall be implemented while ensuring the safety of people and the environment, and in compliance with domestic laws and regulations.
In particular, when discharging ALPS treated water into the sea, we shall make sure to comply with all domestic regulations and laws stipulated in accordance with ICRP recommendations, which are internationally accepted, just like when radioactive liquid waste is discharged from by other countries that have nuclear facilities, including China and Korea. These regulatory standards have been created based on scientific evidence to prevent the discharge of radioactive substances into the environment from impacting people or the environment. And, the International Atomic Energy Agency (IAEA) have deemed these regulatory standards to be “in compliance with international practices.”
Water being stored in tanks on site that have concentrations of radioactive substances, excluding tritium, that do not fulfill regulatory requirements for discharge into the environment shall be re-purified with ALPS, etc. until said concentrations are lower than regulatory standards prior to dilution and discharge.
Thereafter, in order to reduce the concentration of tritium, the ALPS treated water shall be diluted with a volume of seawater more than 100 times the amount of water to be discharged. The radioactive substances for which concentrations have already been sufficiently reduced to meet regulatory standards for discharge into the environment, will be further diluted by a factor of 100 as a result of this process.
The concentration of tritium in discharged water that has been diluted with seawater will be below 1,500Bq/liter, which is much lower than Japan’s standards (60,000Bq/liter) and the World Health Organization’s (WHO) water quality guidelines for drinking water (10,000 Bq/liter).
Furthermore, in light of related international laws and practices, we have performed radiological impact assessments for people and the environment and have disclosed the results of these assessments. We shall also continuously monitor tritium in the environment after discharge and formulate measures to ascertain the state of tritium in the environment. We will also continue to have the International Atomic Energy Agency (IAEA) conduct objective and transparent reviews of this process based on international safety standards. Experts from third-party countries will also participate in these reviews.

There is no difference between water discharged from Fukushima Daiichi Nuclear Power Station and water drained from other nuclear facilities in the respects that it fulfills government regulations pertaining to the discharge of radioactive substances into the environment and the radiological impact on people and the environment is negligible.
When discharging radioactive substances from a nuclear facility into the environment, the types of radioactive substances to be regulated are stipulated for each facility (depending on operational details, reactor type, etc.).
When discharging ALPS treated water from the Fukushima Daiichi Nuclear Power Station into the environment, we confirm that the radioactive substances are at concentrations that fall below government regulations, just like other nuclear facilities.
“Contaminated water yet to be purified” at the Fukushima Daiichi Nuclear Power Station contains radioactive materials not usually detected in drainage water^* from a typical nuclear power station (for example, Strontium-90 and Cesium-137, etc.). However, when discharging of ALPS treated water that has been purified, we make sure that we comply with government regulations.

* Radioactive substances such as Tritium, Cobalt-60, and Manganese-54 may be detected in drainage water from a typical nuclear facility.

In addition, as a result of the tsunami, water from the Fukushima Daiichi Nuclear Power Station may contain impurities such as salt originating from seawater that was brought in by the tsunami, as well as lubricating oil from machinery located in the buildings. When discharging water that contains these impurities into the environment, we confirm that the concentrations of impurities comply with regulations, such as the Water Pollution Control Act. And, the results of the tests are publicly disclosed.

Concentration of carbon-14 in ALPS treated water meets Japanese Government’s regulatory standard that was stipulated in accordance with international standards of radioactive wastes.
Ensuring safety of the public and surrounding environment is a precondition for discharging liquids or gases that contain radioactive substances into the environment from nuclear facilities, and utilities must comply with Government’s regulatory standards which have been stipulated in accordance with the International Commission on Radiological Protection (ICRP) recommendations.
The concentration of carbon-14 in tanks used to store ALPS treated water, etc. (data obtained from a total of 80 tanks analyzed by the end of June 2020) is 42.4 Bq/liter^* on average, while the Japanese Government’s regulatory standard (regulatory concentration limit) is 2,000 Bq/liter.
Even if an adult were to drink approximately 2L of this water without dilution every day for an entire year until the age of 70, the annual dose would only be approximately 0.021mSv, which is well below 1 mSv, the upper limit of annual dose for the public.

*Minimum: 2.53 Bq/liter; Maximum: 215 Bq/liter

Our radiological environmental impact assessment regarding the discharge of ALPS treated water into the sea was performed in compliance with the international standards, which consider the potential accumulation in the environment and the bioaccumulation through the food chain. The results suggest that the impact on public and the environment is extremely small. Furthermore, these results have been verified by the Nuclear Regulation Authority and reviewed by the International Atomic Energy Agency (IAEA).
In our radiological environmental impact assessment regarding the discharge of ALPS treated water into the sea, we have considered the potential accumulation of radioactive substances discharged into the environment and bioaccumulation through the food chain. The result of the assessment, which was performed in compliance with internationally recognized scientific standards, shows that the impact on public and the environment is extremely small^*.
This radiological environmental impact assessment was implemented based on the "Basic Policy on handling of ALPS treated Water at the Tokyo Electric Power Company Holdings’ Fukushima Daiichi Nuclear Power Station (Government decision of April 2021)". As part of the approval process for the application for approval to amend the implementation plan under the Act on the Regulation of Nuclear Source Material, Nuclear Fuel Material, and Reactors, the Nuclear Regulation Authority has confirmed the assessment result.
Furthermore, we have explained our methodology and results of the assessment to the IAEA. In the IAEA's comprehensive report, they confirmed that our assessment method considers long-term releases without underestimating potential impacts, and the resulting impacts on public and the environment are negligible.

* For example, the public impact assessment assumes that an individual is at sea for 120 days a year within a 10 kilometer radius of the Fukushima Daiichi Nuclear Power Station, stays on the coast 3km north of the power station for 500 hours, swims in the sea for 96 hours, and consumes an average of 58 grams of Japanese fish daily. In this scenario, the evaluated radiation dose is less than 1/30,000 of the general public's dose limit (1 millisievert per year). Moreover, for marine organisms like flounder and brown algae, the evaluated impact result is less than 1/1,000,000 of the standard proposed by the International Commission on Radiological Protection (ICRP). For crabs, it's evaluated to be less than 1/10,000,000 of the standard.

Currently, the water that was purified with multi-nuclide removal equipment (ALPS) and has had the concentrations of radionuclides reduced (“ALPS treated water” and “treated water to be re-purified”) is being stored in tanks at the Fukushima Daiichi Nuclear Power Station. The concentrations of major radionuclides in this stored water are analyzed and publicly disclosed on our website, but this data is not used to determine if the water is suitable for discharge.
Click here for the analysis results of the major radionuclides in storage tanks (in Japanese only)

Before discharging “treated water to be re-purified” we shall re-purify this water using multi-nuclide removal equipment (ALPS) to reduce the concentration of all radionuclides, excluding tritium. Treated water to be re-purified will not be discharged as is into the sea.
For the water to be discharged into the sea, after being transferred to the “measurement/confirmation facility”, the concentrations of radionuclides in the water will be analyzed and assessed by our company and third-party agencies, to ensure that the water meets regulatory standards, excluding the standards for tritium. These results are publicly disclosed on our website.
Click here for the Pre-discharge analysis results of the water in the measurement/confirmation tanks

According to our discharge plan, each time before a discharge, we will circulate and agitate the water in the “measurement/confirmation facility” to make the water quality homogeneous. After that, we will take samples of the water to analyze and assess the concentrations of 69 nuclides. In this analysis and assessment, we ensure that the concentrations of 30 nuclides, which could be present in significant amounts even before ALPS treatment, fall well below the Government’s regulatory standards. We will also confirm the concentration of tritium, and check the concentrations of the remaining 38 nuclides (out of the 69 radionuclides, excluding tritium and the aforementioned 30 nuclides) that they are not present in significant amounts.
This discharge plan was confirmed by the International Atomic Energy Agency (IAEA) to be “consistent with relevant international safety standards” as stated in the IAEA’s comprehensive report, which also states that, “the discharge of the ALPS treated water will have a negligible radiological impact on people and the environment”.
Additionally, to check the performance of ALPS, we analyze 64 major nuclides once a week and a total of 64 radionuclides, including the 62 targeted for removal by ALPS, once a year at the ALPS outlet. Based on the analysis results to date, we have confirmed that ALPS can purify the radionuclides to well below the Government’s regulatory standards in a single treatment. Furthermore, the analysis results also show that radionuclides other than the major ones are almost never detected. Thus, we believe that through future treatment with ALPS we can remove the radionuclides in the stored water that are present at concentrations that exceed the Government’s regulatory standards so that such concentration fall below these standards.

Drainage from nuclear facilities in Japan and overseas, including the Fukushima Daiichi Nuclear Power Station, does not violate the London Convention.
The London Convention stipulates measures that should be implemented by member nations to internationally regulate the ocean disposal of waste, which is one of the causes of marine pollution.
The London Convention applies only to “dumping” and defines “dumping” as, “(i) any deliberate disposal at sea of wastes, etc. from vessels, etc.; (ii) any deliberate disposal at sea of vessels, etc.”
This definition has been interpreted to mean that, “drainage from land is not prohibited,” so the drainage from nuclear facilities in Japan and overseas, including the Fukushima Daiichi Nuclear Power Station, does not constitute a violation of the London Convention.

Currently, multi-nuclide removal equipment (ALPS) is comprised of three types of ALPS facilities with total of seven treatment systems (treatment capability of three types of facilities in total: 1,900 m³ per day) that have sufficient treatment capabilities. By switching these treatment systems, we are able to handle problems and conduct inspections while continuing the treatment. These treatment systems are regularly inspected and maintained thereby ensuring ALPS performance over the long-term. If needed, the facilities will also be renovated.

On the Treated Water Portal Site, you can find ALPS treated water discharge records to date and discharge plan, with information such as pre-dilution tritium concentration of ALPS treated water and amount of ALPS treated water discharged into the sea.
Click here to see discharge records to date
Furthermore, you can see status of discharge of ALPS treated water into the sea on the front page of the Treated Water Portal Site. On the page of “dilution/discharge facility conditions”, pre-dilution tritium concentration of ALPS treated water, the amount of ALPS treated water being transferred to dilution/discharge facility, and the amount of seawater being taken in for the dilution are disclosed in real time.
Click here for the details

When discharging the ALPS treated water into the sea, prior to the every discharge, TEPCO, Kaken, an external agency consigned by TEPCO, and the Japan Atomic Energy Agency (JAEA), a third-party based on the Japanese Government’s Basic Policy, confirm the tritium concentration in ALPS treated water and also confirm that the concentration of 30 radioactive substances targeted for measurement/assessment meet the government’s regulatory standards. All of these data are being disclosed to the public. Moreover, the International Atomic Energy Agency (IAEA) corroborates the monitoring implemented by TEPCO as needed. Additionally, we confirm that 44 parameters aside from the radioactive substance concentrations meet effluent standards. We also confirm as part of general water quality analysis that these 44 parameters meet standards pertaining to Fukushima Prefecture’s "Ordinance on Discharge Standards Based on the Air Pollution Control Act and Wastewater Standards based on the Water Pollution Prevention Act" and the “Ordinance Enforcement Regulations Pertaining to the Preservation of the Living Environment in Fukushima".
In particular, prior to the discharge of ALPS treated water, analysis/assessment of 69 nuclides is performed for the water to be discharged after the water has been agitated/circulated in the measurement/confirmation facility to ensure that the water quality is homogeneous. As a result of this analysis, we confirm that the 30 nuclides subject to measurement/assessment, and that have possibility to exist at significant concentrations in water prior to ALPS treatment, fall well below the government’s regulatory standards. Furthermore, we also measure the tritium concentration and confirm that the other 38 nuclides (excluding tritium and 30 nuclides subject to measurement/assessment from 69 nuclides measured prior to every discharge,) are not present at significant levels.

*Added 113m Cadmium to the nuclides to be measured/assessed (From August 2024).
Click here to see a video of an overview of the measurement/confirmation facility
Click here to see pre-discharge analysis results for water in the measurement/confirmation facility analyzed by TEPCO and external agencies consigned by TEPCO
Click here to see the JAEA’s pre-discharge analysis results for water in the measurement/confirmation facility
Click here to see the IAEA’s pre-discharge analysis results for water in the measurement/confirmation facility (results for samples taken on July 10, 2023)
Click here to see measurement/confirmation facility conditions

Prior to the discharge of ALPS treated water into the sea, TEPCO and an external agency consigned by TEPCO (Kaken) analyze the concentrations of radioactive substances in pre-diluted ALPS treated water and confirm that it meets regulatory standards. Furthermore, the Japan Atomic Energy Agency (JAEA), which is designated as a third-party based on the Japanese Government’s Basic Policy, conducts independent analyses and conducts the similar confirmation. Additionally, the International Atomic Energy Agency (IAEA) substantiates TEPCO’s monitoring initiatives as necessary. This figure diagrams a summary of the analyses by third parties at ALPS treated water related facilities.
Click here to see the pre-discharge analysis results from the measurement/confirmation facility
Every day during discharge, TEPCO confirms the tritium concentration by sampling water from the dilution facility seawater pipe, and the IAEA also confirms tritium concentrations at irregular intervals. These results can be found at the following link. During the first three discharges of ALPS treated water (The first discharge was commenced on August 24, 2023, the second discharge was commenced on October 5, 2023, and the third discharge was commenced on November 2, 2023), we confirmed prior to discharge that the tritium concentration of diluted water in the discharge vertical shaft (upper-stream storage) is less than 1,500Bq/liter, which means the water is diluted as designed, and disclosed the results on our website. This analysis is also confirmed by IAEA, and its results are disclosed on IAEA’s website.
Click here to see the analysis results for the discharge vertical shaft water and seawater pipe water
Click here to see IAEA’s analysis results for the discharge vertical shaft

The International Atomic Energy Agency (IAEA) is a related agency within the United Nations that works to ensure the safe and peaceful use of nuclear power. During the IAEA’s safety review of ALPS treated water, the IAEA performs a technical review based on its international safety standards. The characteristics of discharged ALPS treated water, the safety of the discharge process, and the radiological environmental impact on people and environment were reviewed to confirm the safety of the discharge of ALPS treated water.
The IAEA’s international safety standards have been formulated through discussions between all IAEA member states and related agencies, and reflect international consensus about high level of safety needed to protect people and the environment from the harmful impacts of ionizing radiation.
The four review missions conducted as part of the pre-discharge review resulted in five reports. Furthermore, between May and June 2023, the Comprehensive Review that covered a safety review of the Japanese Government’s policy on the handling of ALPS treated water and TEPCO, a review of the Nuclear Regulation Authority, and the IAEA’s analysis results to corroborate the analysis results from TEPCO, was conducted by IAEA. The Comprehensive Report of this safety review was released on July 4 at the same year.

The IAEA Comprehensive Report concluded that:
- The approach to the discharge of ALPS treated water into the sea, and the associated activities by TEPCO, NRA, and the Government of Japan, are consistent with relevant international safety standards.
- The discharge of the ALPS treated water, as currently planned by TEPCO, will have a negligible radiological impact on people and the environment.
Furthermore, the Comprehensive Report states that,
- The IAEA is committed to engaging with Japan on the discharge of ALPS treated water not only before, but also during, and after the treated water discharges occur. IAEA Director General Rafael Grossi commented that “We are going to stay here with you for decades to come… until the last drop of the treated water has been safely discharged”, ”The IAEA will review, inspect and validate the plan’s efficacy over the coming decades”.

TEPCO will continue to fully cooperate with IAEA safety reviews as it strives to ensure the safety and reliability of the discharge of ALPS treated water.
Click here to see “Safety Review by the IAEA"

International Atomic Energy Agency (IAEA)’s safety review of the discharge of ALPS treated water into the sea is conducted by a task force comprised of IAEA workers and international experts from 11 countries: Argentina, Australia, Canada, China, France, Marshall Islands, the Republic of Korea, Russia, the United Kingdom, the United States, and Vietnam.

As part of the safety review of all related aspects of handling discharge of ALPS treated water into the sea conducted by the International Atomic Energy Agency (IAEA), which includes experts from countries all around the world, analyses are conducted on ALPS treated water samples collected on the Fukushima Daiichi Nuclear Power Station and samples from the marine environment at the vicinity of the power station by IAEA laboratories and third-party laboratories selected by the IAEA, in order to corroborate the results data of analysis conducted by TEPCO and Japanese analytical laboratories. The analytical results from each laboratory are compared and published in the IAEA’s reports.
TEPCO will continue to fully cooperate with IAEA safety reviews as it strives to ensure the reliability and transparency of the discharge of ALPS treated water into the sea.
(Reference)
In light of request from Government of Japan, the IAEA has been continuously implementing the Interlaboratory Comparison (ILC) since 2014 in order to support the Government of Japan in ensuring the reliability and transparency of sea area monitoring data. Samples from the marine environment around the Fukushima Daiichi Nuclear Power Station have been jointly collected by the IAEA, and individually analyzed by the IAEA, Japanese analytical laboratories, and third-country laboratories selected by the IAEA, and the IAEA compares the analysis results of each analytical laboratory.

By steadily monitoring seawater and marine products during the discharge of ALPS treated water into the sea in accordance with the Japanese Government’s “Comprehensive Monitoring Plan”, we are confirming the safety of seawater and marine products and are promptly disclosing all of these data to the public. In addition to having Ministry of Environment, Nuclear Regulation Authority and Fukushima prefecture involved in monitoring, we are also striving to ensure transparency and objectivity by going through IAEA‘s review and offering opportunities for local government officials, etc., to witness the monitoring/sampling process.
Monitoring results to date have confirmed that the ALPS treated water is being discharged safely.

Normal measurement of tritium (precision measurement) usually takes from several days to approximately one month to complete. However, in addition to this measurement, we have been conducting “quick tritium measurement”, after the starting the discharge of ALPS treated water into the sea. In "quick tritium measurement”, we obtain analysis results of tritium concentration around the Fukushima Daiichi Nuclear Power Station in one day, by setting the detection limit at 10Bq/liter.
Furthermore, agencies other than TEPCO also perform “quick tritium measurement”, and the analysis results from these agencies are compiled by TEPCO and disclosed via the “Treated Water Portal Site” and the “Overarching Radiation-monitoring data Browsing System (ORBS)”.

ALPS treated water is the result of purification with multi-nuclide removal equipment (ALPS), etc. that reduces the concentrations of radioactive substances, excluding tritium, so that they fall well below Japan’s domestic regulatory standards that were created based on ICRP recommendations. This ALPS treated water is then diluted with a volume of seawater 100 times the amount to be discharged and then discharged into the sea. As a result, the impact of discharge into the sea on the surrounding environment will be negligible.
The results of an ocean diffusion simulation conducted as part of our radiological environmental impact assessment show that areas in which the concentrations of tritium in the environment exceed the natural concentrations of tritium in seawater (0.1~1Bq/liter) are restricted to an area 2~3 km from the power station, and that tritium concentrations in the areas outside this 3km radius do not differ from those in the natural environment. Based on these results, the IAEA’s comprehensive report came to the conclusion that the discharge would have a negligible radiological impact on people and the environment.
Furthermore, since April 2022, we have increased the quantity and frequency of sea area monitoring points used to monitor targeted nuclides, including tritium, and as a result have been able to continually confirm that the discharge of ALPS treated water is not having an impact on the surrounding sea area.

The safety of the discharge of ALPS treated water has been confirmed through the scientific knowledge pertaining to tritium that exists today.
On this basis, we are rearing marine organisms in a seawater environment that includes ALPS treated water in order to demonstrate in an easy-to-understand manner that the tritium concentrations in marine organisms are no different than the tritium concentrations in seawater, in line with existing scientific knowledge.
Specifically, we are rearing marine organisms (flounder, abalone and seaweed) in both seawater and ALPS treated water diluted with seawater (with tritium concentration of about 1,500 becquerels per liter), and are then comparing their growth conditions.
TEPCO’s aim is to deepen the understanding of the general public about the safety of the discharge of ALPS treated water by providing visual proof in the form of actual breeding experiments conducted in ALPS treated water.
Click here to see to learn more about the marine organisms rearing test

Rearing test results to date have confirmed that 1. In seawater to which ALPS treated water has been added, marine organisms grow no differently than those in normal seawater; 2. The tritium concentrations in the bodies of marine organisms reared in seawater to which ALPS treated water has been added does not exceed the tritium concentration in the seawater of the tank in which they are being reared (does not accumulate in their bodies); and, 3. When these organisms are returned to normal seawater, the tritium concentrations in their bodies decreases.
Results 2. and 3. have already been proven through past research conducted in Japan and overseas.
Click here to see to learn more about the marine organisms rearing test

The Japanese Government’s Basic Policy on handling of the ALPS treated water (announced in April 2021), the policy to dilute and discharge the ALPS treated water was indicated. This policy was based on the evaluation of “the Subcommittee on the Handling of the ALPS Treated Water” that “no technologies have been judged as being close to practical use of the Fukushima Daiichi Nuclear Power Station”, and the same view expressed by IAEA. However, the Japanese Government’s Basic Policy also indicated that “new technological trends will be carefully and continuously monitored and if a viable technology emerges, it will be implemented as rapidly as practicable”.
Accordingly, since May 2021, we have been announcing public appeals to domestic and overseas parties for technologies for separating tritium from ALPS treated water via a third-party organization consigned by TEPCO. If a technological proposal submitted to this public appeal is deemed to have the potential to meet all of the requirements for practically separating tritium from ALPS treated water, etc., it will be subject to feasibility studies (to improve the accuracy and reliability of the technology and empirical data, and examine feasibility based upon specific conditions) through which we shall clarify issues that need to be addressed in preparation for practical application.
Please refer to the following link for details about the public appeal project.
Click here for details on the public appeal project