IAEAInternational Atomic Energy Agency

Marine Environment Monitoring

Assessment of IAEA Environment Laboratories on Data provided by

JapanUpdate 12 April

IAEA Environment Laboratories, Monaco

IAEA

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.

• 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.

IAEA

Seawater sampling carried out by Japanese Authorities MEXT

•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 (10-9)•On 4th April MEXT added stations A and B north-west of the sampling point 1•At the sampling points 1-8 levels of I-131 and Cs-137 show a quite a decreasing time trend•More variations are observed at stations 9 & 10

Map 1

IAEA

Seawater sampling carried out by TEPCO

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

• Since 5th of April 6 points situated 15 km off-shore along a north-south transect (TEPCO 5-10)

• The levels of I-131 and Cs-137 at the sampling point TEPCO 5-10 are lower than those at the near-shore stations (below 0.5 kBq/l)

• The levels of I-131 and Cs-137 at the sampling point TEPCO 4-1 are below 20 kBq/l after 9 April)

IAEA

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

IAEA

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 quite a decreasing time 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

IAEA

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 Mirai for two days; visited the laboratory in Tokai and met 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 Mirai for two days; visited the laboratory in Tokai and met the responsibles of the Japan Agency for Marine-Earth Science and Technology (JAMESTEC), MEXT, MOE, MOFA.