The International Atomic Energy Agency (IAEA) Task Force assessing the safety of Japan’s planned discharge of treated water from the Fukushima Daiichi Nuclear Power Station has issued its fifth report. This is part of a series to be released under the IAEA’s multi-year safety review of the proposed Advanced Liquid Processing System (ALPS) treated water discharge. It focuses on Japan’s domestic regulatory review of the water release and includes observations of the Task Force mission to assess Japan’s Nuclear Regulation Authority (NRA) activities, which took place in January.
Japan’s planned discharge of the water, scheduled for this year, is subject to final regulatory approval from NRA. IAEA Director General Rafael Mariano Grossi appointed the Task Force of independent experts and IAEA staff to review the safety of Japan’s plan for the water stored at the Fukushima Daiichi plant against international safety standards. The standards constitute the worldwide reference for protecting the public and the environment from harmful effects of ionising radiation.
The review of regulatory aspects is one component of the international Task Force’s three-pronged review, the other two being the review of technical aspects and conducting independent sampling and analysis. The Task Force noted a number of key outcomes from the mission:
- The NRA agreed to require Tokyo Electric Power Company (Tepco) to review optimisation of protection for the discharge of ALPS treated water based on operational experience and associated monitoring following the start of the discharges.
- The NRA further agreed to establish a framework for revisiting discharge limits, operating limits, and conditions to reflect the optimization of protection, in a similar manner, if needed.
- The Task Force acknowledged that the NRA has conducted a review to determine that sufficient evidence exists that the source term contains all the radiologically significant radionuclides and that it does not exclude, in the assessment, any radionuclides that could be significant contributors to the dose to the public or to flora and fauna.
- That NRA’s approach to enforce controls on the occupational exposure of Tepco’s employees is sufficient for compliance with international safety standards.
The Task Force acknowledged that the NRA has focused on involving the public in the regulatory review process. The Task Force will continue to review how public consultations and the involvement of interested parties are handled by the NRA as the regulatory process continues. “The Task Force has seen that the NRA serves as the independent regulatory body within Japan and holds the responsibility for assessing the safety of the proposed discharge of ALPS treated water,” said Gustavo Caruso, Director of the IAEA Department of Nuclear Safety & Security, and Chair of the Task Force. “However, we will continue to review how the NRA conducts its regulatory process leading up to, and after, the proposed discharges of treated water.”
The Task Force’s safety review continues. One more report will be issued on independent sampling and analysis aspects, before the final comprehensive report detailing the collected findings and conclusions of the Task Force is issued. Japan intends to start discharging the ALPS treated water in 2023, pending Tepco’s completion of necessary domestic regulatory actions.
Meanwhile, Yomiuri Shimbun Senior Writer Futoshi Mori visited Fukushima Daiichi NPP where he was shown the measures being taken to monitor the situation. He said some 90,000 samples of radioactive materials are measured and analysed in a year. Tepco has expanded the number of monitoring points where seawater is analysed in preparation for the discharge of treated water into the ocean, he noted. “The purpose of the strengthened monitoring is to confirm the safety of the water before and after the discharge, and to disseminate the results to the public.”
“To prevent mistakes, we have introduced a system of centralised management using QR codes,” explained Junichi Suzuki, the group manager in charge. “We manage all information from registration to results, including when and where samples were collected, which radioactive materials were measured, who analysed them, and which equipment was used.” Since 2019, the calculation of concentrations is being done by software instead of humans. Suzuki told Mori that work efficiency has improved dramatically, and mistakes have been eliminated.
Mori was shown the treated water analysis site, where a female analyst was working while wearing goggle-like glasses. “These are smart glasses,” Suzuki said. “They make it possible to see each step of the workflow.”
The analyst followed procedures projected inside the smart glasses. She held a container of treated water that had a QR code affixed to it, then read off the date and time of collection on the label. A camera attached to the smart glasses captured the QR code and the label. The video images were projected onto the computer of a person in charge in a separate office building, who could also be seen on a screen, and who then used a keyboard to input the date and time of collection.
When both the analyst’s voice and keyboard input match, the information is registered in the system and the analysis began. Each time the analyst completed a task, she said, “Good.” The smart glasses then instruct the analyst on the next step.
The radioactivity levels of samples vary, from high to low. At the chemical analysis facility, the staff analyse samples with low radioactivity levels, such as treated water, seawater from the surrounding area, and purified water from subdrainage. There are 31 analysts, and together they register an average of about 100 samples a day.
“Moving deeper into the room, there were devices that measure tritium in the treated water and other radioactive materials that emit beta rays.” There are 14 of these blue and white devices. Their number has increased as more analyses have been performed. Behind them were 12 instruments for measuring gamma rays, for example from caesium-137, with analysis specimens placed behind 15-cm-thick lead doors.
There were also two sturdy pink devices, recently introduced to measure iron-55 (Fe-55), a radioactive isotope of iron, which has been added as an item for detection among the 69 nuclides of radioactive materials measured before each discharge of treated water. “Iron-55 is a radioactive material that emits only very low-energy gamma rays,” Suzuki said, “so this is the device for measuring it.”
Tepco has increased the number and frequency of monitoring points and lowered the detection limit for tritium, which is most abundant in the treated water. The number of monitoring points has increased by 85 to about 260, and analysis is being conducted sequentially.
The tritium detection limit, which was previously 0.4 becquerels per litre, has been lowered to 0.1 becquerels in accordance with the standards set by the Environment Ministry and other organisations. However, the analysis results for the 0.1 level take about two weeks longer than results for the 0.4 becquerel level, obtainable in about three days.
The reason for measuring the concentration of tritium in the treated water is that the ALPS system cannot remove it. Tepco will therefore dilute the treated water with a large amount of seawater to reduce the concentration to less than 1,500 becquerels per litre before discharging it. The treated water will be discharged one kilometre offshore, where it will be quickly dispersed by the tidal currents, and the concentration is expected to further drop dramatically.
Mori also visited the construction site for the discharge infrastructure along the sea on the north side of the premises. Three thick pipes through which large amounts of seawater are carried extend from seawater pumps. At the end of the pipes is a huge header pipe through which the treated water, which flows through a transfer pipe from higher ground, will be mixed with the seawater. The diluted treated water then enters the upstream water tank, overflows into the downstream water tank next to it, and goes through the tunnel at the bottom to the discharge outlet offshore.
Just before discharging the water, the tritium level will be measured. The measurement of radioactive materials in seawater and in fish after the discharge has also been enhanced. “Nevertheless, once the release of the treated water begins, there is concern that reputational damage will once again occur, both domestically and internationally. Even if safety can be proven, it will take time to reassure the public, Mori concludes.
Image: An analyst at TEPCO’s Fukushima No.1 nuclear power plant prepares to measure tritium in ALPS treated water (courtesy of Japan News)