An aerial view shows the storage tanks for treated water at the tsunami-crippled Fukushima Daiichi nuclear power plant in Okuma town, Fukushima, Japan

(Reuters) -Japan said late on Monday it had responded to inquiries from China and Russia about the ocean discharge of wastewater from the Fukushima nuclear power station, owned by Tokyo Electric Power Company Holdings (Tepco).

The Japanese government has shared its responses to the two neighbouring countries in a document dated Aug. 18 and posted on the International Atomic Energy Agency's website.

Tepco has been filtering the contaminated water, using machines called Advanced Liquid Processing System (ALPS), to remove isotopes, leaving only tritium, a radioactive isotope of hydrogen that is hard to separate from water. Tepco will dilute the water until tritium levels fall below regulatory limits before pumping it into the ocean from the coastal site.

Below are key extracts from the Japan's response:

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DISPOSAL OF FUKUSHIMA WATER

"The ALPS treated water will meet both Japanese regulatory standards based on relevant international standards. In other words, tritium levels in the treated water and diluted water will be below those considered safe for drinking."

"Meanwhile, it is not the practice of any country to drink the water discharged from nuclear facilities."

"The International Atomic Energy Agency (IAEA) has concluded... that the approach to the discharge of ALPS treated water into the sea and the associated activities by Tokyo Electric Power Company Holdings, the Nuclear Regulation Authority (NRA) and the government of Japan, are consistent with relevant international safety standards and the discharge... will have a negligible radiological impact on people and the environment."

RELEASE OPTION

"There is insufficient additional storage capacity in existing tanks (97% full); constructing more storage tanks is not feasible at the FDNPS (Fukushima Daiichi Nuclear Power Station), as all available space for tanks at the site is already occupied."

"Use of storage tanks in the long term is dangerous, as the surrounding areas are prone to earthquakes, which would put tank integrity at risk."

"The discharge into the sea was selected because it can be implemented more reliably as it has a proven track record in domestic and overseas nuclear facilities, it is easy to forecast the diffusion behaviour, and it is the easiest for monitoring of any potential impact on the environment."

NORMAL OPERATION AND WATER FROM A NUCLEAR ACCIDENT

"International safety standards do not distinguish between water released from normal operation, and water from a facility that has suffered an accident. This is because what matters is the content of the water to be discharged, not its source.

The IAEA has confirmed... that the planned discharge of the ALPS treated water... will not harm people or the environment, including the marine environment."

ANNUAL DISCHARGE LIMITS

"Japan does not consider it necessary to set such limits because Japan will ensure that the ALPS system reliably removes nuclides other than tritium below the regulatory standards before any individual batch of ALPS treated water is discharged.

This will be ensured through comprehensively sampling each batch of ALPS treated water prior to beginning the dilution and discharge of that water."

RELIABILITY OF ALPS SYSTEM

"The ALPS performance has been approved by the NRA (the Nuclear Regulation Authority), an independent regulator of Japan. Since 2019, the ALPS system has functioned stably and effectively enough to purify the water to meet the regulatory standards."

"No discharges of ALPS treated water will be made from any tank to the sea unless the water from that tank meets the discharge standards instituted by the NRA and reviewed by the IAEA as part of its safety review.

Because every batch will be tested, and actual concentration levels will be determined, there will be no need to estimate or project the nuclide concentrations in any batch before discharge."

CREDIBILITY OF MONITORING RESULTS

"The IAEA and several third-country laboratories selected by the IAEA analyzed the samples of treated water taken in March 2022... these findings provide confidence in Tepco's capability for undertaking accurate and precise measurements related to the discharge of ALPS treated water.

Furthermore, based on the observations of the IAEA, Tepco has demonstrated that it has a sustainable and robust analytical system in place to support the ongoing technical needs at the Fukushima facilities during the discharge."

EXTERNAL SUPERVISION IN MONITORING

"The Government of Japan is of the view that the participation of the third-country laboratories as part of the IAEA review will ensure the credibility and transparency of Japan's monitoring.

Japan respects the IAEA's decision in this regard, and therefore is of the view that Japan's individual invitation of stakeholders for monitoring is unnecessary."

DIRECT PARTICIPATION BY CHINA AND RUSSIA IN THIRD-PARTY MONITORING

"The Government of Japan is of the view that the independent analysis and corroboration activities by the IAEA and third-country laboratories will assure the quality of, and provide confidence in, the results of Japan's source monitoring and environmental monitoring."

"Japan repeatedly proposed individual briefing sessions to Chinese nuclear experts as well as government officials with a view to engaging in scientific discussion and promoting China's understanding of the matter.

These offers are in line with Japan's commitment to ensuring maximum transparency with regard to the safety of the planned discharge. It is regrettable that such meetings have yet to be realized."

ENVIRONMENTAL MONITORING

"Should a problem be detected during the monitoring process such as detection of unusual value of concentration of the radioactive materials, Japan will take appropriate measures, including immediate suspension of the discharge."

PARTICIPATION BY CHINA AND RUSSIA IN DECISION-MAKING OF WATER RELEASE

"The IAEA in its Comprehensive Report positively noted the efforts that Japan has made to provide information to and engage in consultations with the interested parties including both international and domestic ones, and to conduct significant outreach activities to ensure transparency."

TERM OF ALPS TREATED WATER

"The ALPS treated water is not 'contaminated water' as the concentration of radioactive materials is far below the regulatory standards. These two terms should not be mixed up."

(Reporting by Yuka ObayashiEditing by Katya Golubkova and Gerry Doyle)