IAEAInternational Atomic Energy Agency

Marine Environment Monitoring

Assessment of IAEA Environment Laboratories on Data from the Marine

Environment provided by JapanUpdate 19 April

IAEA Environment Laboratories, Monaco

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General comments

• The contamination of the marine environment has occurred both through atmospheric fallout or washout with precipitation, and through discharges of contaminated water into the sea

• Authorised discharge of low level contaminated water (4 April)

• TEPCO and MEXT are continuing to conduct programmes for sea water sampling and to perform measurements.

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New plan for environmental assessment announced by Japanese authorities

NISA directions to TEPCO: In order to better understand the potential long term effects of the discharge of radioactive material to the marine environment, on 15 April, NISA directed TEPCO to:

• continue monitoring at current and additional sampling locations;• sample biota (e.g. fish, shellfish, etc.) from the vicinity of the

NPS;• perform an environmental impact assessment;• present the results of these actions to the public.

IAEA Environment Laboratories in collaboration with the other IAEA Divisions are ready to assist and collaborate with Japan, if requested.

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Seawater sampling carried out by TEPCO

• TEPCO is sampling four near- shore stations (TEPCO1-4)

• Since 5th of April six points situated 15 km off-shore along a north-south transect (TEPCO 5-10)

• Following a Directive from NISA, on 16 April TEPCO announced that they will increase the number of sampling points. Four points will be added at 3 km from the coast and two points at 8 km from the coast.

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Seawater sampling carried out by TEPCO

• Since 9 April the levels of I-131 and Cs-137 at the sampling points TEPCO 5-10 are lower than those at the near-shore stations (below 0.5 kBq/l) with a decreasing trend

• Since 9 April the levels of I-131 and Cs-137 at the sampling points TEPCO No. 1 – 4 are below 20 kBq/l with a decreasing trend

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Concentrations in sea water near discharge point of TEPCO 1-4

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Concentrations in sea water further off-shoreabout 15 km from the coast

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Seawater sampling carried out by Japanese Authorities MEXT

• North-South transect about 30 km offshore, sample locations separated by 10 kilometres, surface seawater sampled

• Additional sampling stations at 10 and 20 km offshore, for which both surface and bottom seawater are sampled (No. 9 and 10)

• On 4th April MEXT added stations A and B north-west of the sampling point 1 after discussion with the IAEA Environment Laboratories, Monaco

Map 1

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• 15th April showed that Cs-137 and I-131 were detected at MEXT 4, 6 and 8. The highest concentrations were recorded at MEXT 4 (below 200 Bq/l for Cs-137 and about 160 Bq/l for I-131). At MEXT 6 and 8 sampling locations both Cs-137 and I-131 were reported at levels below about 40 Bq/l.

• The results reported on 19th April (sampling date 17th April) showed that at the stations MEXT 5, 7 and 9, Cs-137 and I-131 are below 90 Bq/l.

• Both Cs-137 and I-131 are “not detectable” at MEXT A and B.

Seawater sampling carried out by Japanese Authorities MEXT

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Conclusions

• The highest levels are still measured close to the coast, namely 30 m, 330 m and 10 km near-shore even though with a decreasing trend.

• Concentration data from about 30 km off-shore show a generally decreasing temporal trend

• It can be expected that, if no additional releases occur, the levels measured at the stations 30 km off-shore will continue to decrease significantly by dilution into deeper layers and dispersion by ocean currents

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Conclusions

• One marine expert from IAEA Environmental Laboratories, Monaco has been in Japan to review and advise on marine sampling and measurements. He was on the research vessel R/V MIRAI for two days; he visited the laboratory in Tokai and met and briefed in Tokyo the responsibles of the Japan Agency for Marine-Earth Science and Technology (JAMESTEC), MEXT, MOE, MOFA.

• One marine expert from IAEA Environmental Laboratories, Monaco has been in Japan to review and advise on marine sampling and measurements. He was on the research vessel R/V MIRAI for two days; he visited the laboratory in Tokai and met and briefed in Tokyo the responsibles of the Japan Agency for Marine-Earth Science and Technology (JAMESTEC), MEXT, MOE, MOFA.