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FAQ on the Contaminated Water Issue

Q1: Please explain the impact of the leaked radioactive materials on the sea.

A1: (September 16, 2014)

  • In July 2014, TEPCO announced that underground water including radioactive materials had leaked into the port at Fukushima Daiichi Nuclear Power Station (NPS). However, the concentrations of radioactive materials measured at the entrance of the same NPS and outer sea area a year ago (September 2013) were either undetectable or remained at a level lower than the Guidelines for Drinking-water Quality set by the World Health Organization (WHO).
  • The International Atomic Energy Agency (IAEA) also recognized that the contamination is limited to the interior of the port.
    The IAEA expert team that visited the site in December 2013 also recognized that the contamination was limited to the interior of the port of Fukushima Daiichi NPS.
  • As a result of the countermeasures taken after the leakage (including ground solidification for revetments using sodium silicate), the outflow of radioactive materials has become even lower* and the concentration inside the port is either undetectable or is lower than the Guidelines for Drinking-water Quality set by the WHO, except for some areas.
    *It is estimated that the amount of leaked strontium and cesium has declined to about one third and one tenth, respectively, compared to the amounts measured a year ago. It has been implied that trillions of becquerels of radioactive materials are still flowing into the sea; however, the concentration of radioactive materials in the sea is at a level that meets the Guidelines for Drinking-water Quality, except for some areas of the port.
  • Additional measures will be taken for further improvement.
    The underground water is to be pumped up from the sub-drains near the buildings for purification and drainage and sea-side impermeable walls are to be installed. The outflow of radioactive materials will decrease further once such measures are completed.

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Q2: Radioactive materials are sometimes detected and sometimes not detectable. What kind of analysis method is adopted?

A2: (December 5, 2014)

  • TEPCO is monitoring the surrounding sea based on the Comprehensive Radiation Monitoring Plan.
  • “Daily analysis” and “detailed analysis” are conducted.
    The daily analysis is conducted to ensure that radioactive materials are not leaking out, and is focused on promptness (conducted every day; lower detection limit: 1Bq/L). The detailed analysis determines the status of radioactive materials released to the environment, including their diffusion and movement (conducted once a week; lower detection limit: 0.001Bq/L).
  • The detailed analysis may detect radioactive materials that were not detectable by the daily analysis
    Compared to the daily analysis, which focuses on promptness, the detailed analysis can detect radioactive materials at a lower level and thus may detect those which were not detectable by the daily analysis. In addition, certain differences in measurement results may be seen.
  • The seawater outside the port of Fukushima Daiichi Nuclear Power Station (NPS) meets the international standard for drinking water.
    In the detailed analysis of the seawater outside the port of Fukushima Daiichi NPS, radioactive materials were not detected, or even when they were detected, the values were at a level much lower than the Guidelines for Drinking-water Quality set by the World Health Organization (WHO).
  • The Government of Japan will further advance the countermeasures against contaminated water and reduce the impact on the ocean, as well as to present accurate information so as to prevent harmful rumors.

*There were some newspaper reports about the analysis method and announcements of results of sea water monitoring related to TEPCO’s Fukushima Daiichi NPS. As some of them may cause misunderstanding among readers, the Government of Japan now explains the facts in a Q&A format.

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Q3: Is there any difficulty because of “frozen soil impermeable walls” that have not been frozen yet?

A3: (August 16, 2015)

  • The as-yet unfrozen sections of the plant refers to a separate issue.
    There are underground tunnels called trenches (reinforced concrete structures about 4m wide and tall, containing pipes and cables) on the sea-side of the buildings of Fukushima Daiichi NPS. Contaminated water leaked into these trenches immediately after the accident; however, the removal of the contaminated water by filing the trenches has been completed. The contaminated water was to be frozen at the joints where the trenches meet the buildings (also containing contaminated water), in order to make partitions, before pumping up the contaminated water from the trenches. However, some sections remain unfrozen as of August 16, 2015.
  • Since the flowing water is considered to be the cause of the phenomenon, the flow of water will be controlled by improving the pumps and utilizing filling materials in unfrozen sections.
  • The construction of frozen soil impermeable walls will steadily continue.
    The installation of frozen soil impermeable walls is, on the other hand, a measure intended to prevent an increase in contaminated water contained in the buildings by enclosing the buildings within The frozen soil impermeable walls, creating a barrier to groundwater and thereby decreasing the volume of groundwater flowing in. The full-scale construction work started on 2 June, 2014. The installation work of the freezing duct at land-side sites is completed, and a pilot land-side freezing operation, where the freezing operation requires more time, has been underway since 30th April, 2015.
  • In the trenches, the flowing water itself was to be frozen. The frozen soil impermeable walls, on the other hand, are structures in which all the soil, including underground water is to be frozen. An experiment conducted near the buildings of Fukushima Daiichi NPS has already confirmed that the walls are indeed capable of being frozen and keeping the water out.
  • Although it is possible that the construction of frozen soil impermeable walls (which would run across the trenches) could be disrupted if the removal process of the contaminated water in the trenches fails, no delays have occurred to this point. The Government of Japan will promote multi-layered measures for removing the contaminated water without delay.

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Q4: TEPCO has reported that the water decontamination work has been delayed. Is it true that the decontamination equipment is continuing to have some troubles?

A4: (February 3, 2015)

  • In order to decrease the risks associated with the contaminated water stored in the tanks, efforts are being advanced to remove as much radioactive materials from inside the tanks as possible.
  • The Government is advancing multi-layered measures for decontamination of contaminated water utilizing several facilities that can remove strontium from the water, in addition to the multi-nuclide removal equipment (ALPS) as well as other high-performance multi-nuclide removal equipment.
  • Although ALPS and other high-performance multi-nuclide removal equipment can substantially remove radioactive materials, they cannot be utilized to the full extent due to the need to replace the absorption tower (equipment to absorb and remove radioactive materials) more often than initially expected. Therefore, it is unlikely to complete the decontamination of all contaminated water within FY2014 as TEPCO originally scheduled. The decontamination process is expected to be completed in May this year if it proceeds at the current pace (except for the water contaminated during the initial period of the accident itself (approx. 20 thousand tons), which is mixed with seawater). The water which has undergone strontium removal will then also be treated by the multi-nuclide removal equipment (ALPS) as the second decontamination process. (The process is estimated to be finished in about one year following the completion of decontamination of the contaminated water stored in the tanks.)
  • As of April 9, 2015, more than 80% of the contaminated water stored in the tanks has already been decontaminated. More than 90% of radioactive materials are removed from the contaminated water through the decontamination process.

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Q5: Recently, there have been many serious accidents involving workers. How will these accidents affect the future work schedule?

A5: (February 3, 2015)

  • There were two fatal accidents and one serious accident involving workers at three TEPCO nuclear power stations on January 19 and 20, 2015. TEPCO suspended all works, except for processing of contaminated water and other related works, from January 20 in order to inspect the safety of the worksites.
  • At Fukushima Daiichi NPS, TEPCO restarted the works on February 3 at the places where safety had been confirmed and improvement measures had been taken.
  • We regard safety as the top priority in advancing decommissioning and contaminated water measures, and will strive to decrease risks.

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Q6: Is there any possibility that the contaminated water will penetrate into deeper layers (permeable layers) due to the presence of deep wells?

A6: (January 29, 2015)

  • High-concentration contaminated water does exist inside the building. However, in order to prevent its leakage, the water level inside the building is controlled at a lower level than the groundwater level near the building.
  • Radioactive materials have been detected in a shallow groundwater near the building due to the impact of the initial events of the nuclear accident, such as explosions. However, the concentration is much lower than that of the contaminated water detected inside the building.
  • The permeable layers in which the groundwater is flowing are formed and comprised of multiple layers, including intermediate impermeable layers. Even in the second permeable layer, with which a part of the building’s base is in contact, (alternate layers; OP -10 to 20 meters), radioactive materials are either undetectable or very low.
    *O.P: Reference Seawater Level at Onahama Point
  • There are 10 deep wells that exceed 200m deep near the mountainside boundary of the site. However, all of them are considerably distant from the building where the contaminated water is accumulating and it is quite unlikely that the contaminated water will penetrate into the deeper layers due to the presence of deep wells.

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Q7. Does the International Atomic Energy Agency (IAEA) require Japan to discharge ALPS-treated water containing tritium into the sea?

A7: (February 18, 2015)

  • Radioactive materials in the contaminated water at the Fukushima Daiichi NPS are removed using decontamination equipment, including ALPS (multi-nuclide removal equipment). However, since the existing equipment is not capable of removing radioactive hydrogen (tritium), the treated water has been stored in tanks. The handling of contaminated water containing tritium has been an issue, as storing such water over the long term entails some risks.
  • When the IAEA review mission visited Japan in February 2015, it advised Japan to consider “all options, including the possible resumption of controlled discharges to the sea,” in line with the advice it gave during its last visit from November to December 2013. This advice was made to request Japan to consider “all options,” but this was not meant to request Japan to take any specific disposition of the water.
  • The Government has established the Tritiated Water Task Force under the Committee on Contaminated Water Countermeasures to examine and consider various options for the handling of the water, including injection in the ground, discharge into the atmosphere or the sea, and burying underground.
  • At the same time, the Government has also launched the development of tritium separation technologies. Based on the advice from the IAEA, the Government will continue to examine a wide range of options concerning the handling of contaminated water containing tritium.

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Division in Charge

Nuclear Accident Response Office, Electricity and Gas Industry Department, Agency for Natural Resources and Energy

Last updated:2015-08-31
Ministry of Economy, Trade and Industry
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