IAEA says Japanese data on Fukushima marine samples is accurate

3 August 2021

Japanese laboratories monitoring radionuclides in seawater, marine sediment and fish near the Fukushima Daiichi NPP produce reliable data, demonstrating a continued high level of accuracy and competence, according to an International Atomic Energy Agency (IAEA) report released on 30 July, covering 2017-20.

The IAEA has worked with the Japanese laboratories since 2014, following a request by the Japanese government to assist it in ensuring that its sea area monitoring around Fukushima Daiichi maintains a high quality, and is comprehensive, credible and transparent. The first phase of the Marine Monitoring Confidence Building and Data Quality Assurance project covered the years 2014 to 2016. It also found that Japan produced reliable data.

In this second phase of the project, the Agency 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 in the proximity of the Fukushima plant. IAEA and international experts observed the collection of samples during the four missions in order to support the quality assurance of radioactivity data collection and analysis.

“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 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”.

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 Canada and and Switzerland that are part of the network of Analytical Laboratories for the Measurement of Environmental Radioactivity (ALMERA), which provided additional international expertise and transparency. The results of the analyses were submitted to IAEA, which carried out a compilation and a statistical evaluation at its Environment Laboratories to assess agreement.

“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. The results also demonstrate a high level of consistency among the Japanese laboratories and with laboratories in other countries and the IAEA,” said Florence Descroix-Comanducci, Director of the IAEA’s Environment Laboratories in Monaco.

Proficiency tests and ILCs are standard methods for laboratories to assess the quality of their measurement results in comparison with those of other laboratories, and to identify any improvement that may be needed. The IAEA runs similar exercises with other analytical laboratories worldwide to improve and maintain high quality analytical capabilities. 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.

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