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Japanese Data on Marine Samples Near Fukushima Reliable, IAEA Report Concludes


Collection of seawater samples near the Fukushima Daiichi Nuclear Power Plant. (Photo: IAEA)

Japanese laboratories analysing seawater, marine sediment and fish samples from near the Fukushima Daiichi Nuclear Power Plant in Japan produce reliable data, according to an IAEA report released today.

“Following the six missions organized in 2014-2016, the IAEA confirms that Japan’s sample  collection procedures follow the appropriate methodological standards required to obtain representative samples,” the report states. It further points out that the results obtained in interlaboratory comparisons “demonstrate a high level of accuracy and competence on the part of the Japanese laboratories involved in the analyses of radionuclides in marine samples for the Sea Area Monitoring programme.”
Interlaboratory comparisons and tests involve laboratories separately testing and analysing samples and then comparing results and procedures to determine their reliability and accuracy. Seven Japanese laboratories and three labs from outside Japan participated in the comparisons. The latter included the IAEA’s Environment Laboratories in Monaco as well as laboratories from Ireland and New Zealand that are part of the network of Analytical Laboratories for the Measurement of Environmental Radioactivity (ALMERA), which provided additional international expertise and transparency. 

Collection of the fish samples from the fish landing port of Onahama. (Photo: IAEA)

“Over 98% of the results were not significantly different from each other, which means the Japanese laboratories involved in the programme demonstrate a high level of consistency amongst themselves and with laboratories in other countries and the IAEA,” said Iolanda Osvath, Head of the IAEA’s Radiometrics Laboratory.

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 project is a follow-up activity to recommendations made on marine monitoring in a report by the IAEA in 2013 related to the decommissioning of the Fukushima Daiichi Nuclear Power Station, which reviewed Japan's efforts to plan and implement the decommissioning of the plant.The project has now been extended for another four years. The next steps will build on the already completed work and involve more interlaboratory comparisons and proficiency tests.

Preparation of the fish samples before measurement of their radioactivity level. (Photo: IAEA)

Recent results

The most recent interlaboratory comparison performed late last year involved seawater samples and six batches of fresh fish caught near the Fukushima Daiichi Nuclear Power Plant. The seawater samples were analysed for tritium (hydrogen-3), strontium-90, caesium-134 and caesium-137 by the Japan Chemical Analysis Center (JCAC), the Geo Science Laboratory (GSL), Japan, KANSO Co., LTD., Japan and the IAEA Environment Laboratories. The fish samples were analysed for caesium-134 and caesium-137 by the Marine Ecology Research Institute (MERI) in Onjuku, Japan, JCAC, the Japan Frozen Foods Inspection Corporation (JFFIC) and the IAEA Environment Laboratories.

Sample analysis results (example): Good agreement is shown between activity concentrations of caesium-137 in fish samples measured by laboratories in Japan (JFFIC, JCAC, MERI) and the IAEA. The yellow bar represents the reference value based on the mean of the four results. Caesium-137 activity concentrations were low in all samples, but particularly in samples 3 and 4 they could only be detected with very long measurement times.

In the proficiency test exercises, the IAEA prepares test samples of low radioactivity seawater and requires the participating laboratories to measure its level of radioactivity. The amount of radioactivity in these so-called ‘spiked samples’ is not known to the participating laboratories, who report their methods and results to the IAEA. Over 50 laboratories worldwide, including 17 Japanese laboratories, participated in these exercises. Proficiency test results published so far for this project are available on the IAEA website

The IAEA runs similar exercises for analytical laboratories worldwide in order to improve and maintain high quality analytical capabilities.

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