Monitoring Fukushima radiation on land and sea

30 July 2021

Japanese laboratories monitoring radionuclides in seawater, marine sediment and fish near the damaged Fukushima Daiichi nuclear power plant continue to produce reliable data, according to a new International Atomic Energy Agency (IAEA) report. Meanwhile, Tokyo Electric Power Company plans to rear fish in treated radioactive water from the plant to demonstrate its safety. A University of Georgia study has shown that radioactive contamination in the Fukushima Exclusion Zone can be measured through its resident snakes.

Seawater samples being taken near the Fukushima Daiichi plant (Image: IAEA)

The IAEA has since 2014 organised missions to support the collection of marine samples for interlaboratory comparisons of radioactivity analyses. The first phase of the Marine Monitoring Confidence Building and Data Quality Assurance project covered the years 2014 to 2016. It found that Japan produced reliable data on marine samples near Fukushima Daiichi plant.

In this second phase of the project, the IAEA carried out a range of activities focused on marine monitoring data quality, including interlaboratory comparisons (ILCs) of seawater, sediment and fish samples collected in four sampling missions conducted from 2017 to 2020 near the Fukushima Daiichi plant.

ILCs involve different laboratories separately testing and analysing samples and then comparing results and procedures to determine their reliability and accuracy. The samples in the second phase of the project were analysed at 12 laboratories in Japan, at the IAEA Environment Laboratories in Monaco and two laboratories in other Member States (in Canada and Switzerland) that are part of the network of Analytical Laboratories for the Measurement of Environmental Radioactivity.

"Following these ILCs, the IAEA can confidently report that Japan's sample collection procedures follow the appropriate methodological standards required to obtain representative samples," the new report states. It added that "the results obtained demonstrate a continued high level of accuracy and competence on the part of the Japanese laboratories involved in the analyses of radionuclides in marine samples for the (country's) Sea Area Monitoring Plan".

"It can be concluded that over 97% of the results were not significantly different from each other, and this shows that the participating Japanese laboratories have the capacity to accurately analyse the samples," said Florence Descroix-Comanducci, director of the IAEA's environment laboratories in Monaco. "The results also demonstrate a high level of consistency among the Japanese laboratories and with laboratories in other countries and the IAEA."

The IAEA Marine Monitoring Confidence Building and Data Quality Assurance collaboration with Japan has been extended for a further two years in order to conduct additional ILCs and proficiency tests and build on the already completed work.

Impact on marine life

At the Fukushima Daiichi site, contaminated water is treated by the Advanced Liquid Processing System (ALPS), which removes most of the radioactive contamination, with the exception of tritium. This treated water is currently stored in tanks on-site. The total tank storage capacity amounts to about 1.37 million cubic metres. As of 15 July, almost 1.27 million cubic metres of treated water were being held in the storage tanks. All the tanks are expected to be full around the summer of 2022.

In April, the Japanese government announced its formal decision that the treated water stored at the Fukushima Daiichi site will be discharged into the sea. The basic policy calls for the ALPS-treated water to be discharged "on the condition that full compliance with the laws and regulations is observed, and measures to minimise adverse impacts on reputation are thoroughly implemented".

Japan intends to start releasing the treated water in early 2023, and the entire operation could last for decades.

Tokyo Electric Power Company yesterday announced plans to rear fish, shellfish and seaweed in seawater containing ALPS-treated water. The test is aimed at aimed at easing safety concerns about the release of the water into the sea.

Information will be gathered on the occurrence of health-related abnormalities, as well as the hatching rate of eggs and the survival rate of matured fish. A comparison will also be made of the concentration of radioactive materials, including tritium, in the water used for the trial and the subjects' bodies.

The test is due to begin in the second quarter of 2022. "Rearing is planned to be continued for a while after discharge has been initiated," the company said.

Reptilian receptors

Meanwhile, a study from the University of Georgia (UGA) has shown that radioactive contamination around the Fukushima plant can be measured through tracking snakes. Rat snakes, it says, travel short distances and can accumulate high levels of radionuclides, making them an effective bioindicator of residual radioactivity.

According to the researchers, the snakes' limited movement and close contact with contaminated soil are key factors in their ability to reflect the varying levels of contamination in the area. Tracked snakes were found to move an average of just 65 metres per day.

The team tracked nine rat snakes using a combination of GPS transmitters and manual very-high frequency tracking. The researchers identified 1718 locations of the snakes while tracking them for over a month in the Abukuma Highlands, approximately 15 miles northwest of the Fukushima Daiichi plant.

The new study's findings reinforce the team's previous study published in 2020, which indicated the levels of radiocaesium in the snakes had a high correlation to the levels of radiation in the soil where the snakes were captured.

"Snakes are good indicators of environmental contamination because they spend a lot of time in and on soil," said James Beasley, associate professor at of UGA's Savannah River Ecology Laboratory (SERL) and the Warnell School of Forestry and Natural Resources. "They have small home ranges and are major predators in most ecosystems, and they’re often relatively long-lived species."

"Our results indicate that animal behaviour has a large impact on radiation exposure and contaminant accumulation," said Hanna Gerke, an alumna of SERL and Warnell. "Studying how specific animals use contaminated landscapes helps increase our understanding of the environmental impacts of huge nuclear accidents such as Fukushima and Chernobyl."

Researched and written by World Nuclear News