International Atomic Energy Agency Japanese Earthquake Update, 15 March (11:25 UTC)

Vienna, Austria–(ENEWSPF)–15 March 2011. 

Fukushima Daiichi Nuclear Power Plant Update

Radiation Dose Rates Observed at the Site

The Japanese authorities have informed the IAEA that the following radiation dose rates have been observed on site at the main gate of the Fukushima Daiichi Nuclear Power Plant.

At 00:00 UTC on 15 March a dose rate of 11.9 millisieverts (mSv) per hour was observed. Six hours later, at 06:00 UTC on 15 March a dose rate of 0.6 millisieverts (mSv) per hour was observed.

These observations indicate that the level of radioactivity has been decreasing at the site.

As reported earlier, a 400 millisieverts (mSv) per hour radiation dose observed at Fukushima Daiichi occurred between units 3 and 4. This is a high dose-level value, but it is a local value at a single location and at a certain point in time. The IAEA continues to confirm the evolution and value of this dose rate. It should be noted that because of this detected value, non-indispensible staff was evacuated from the plant, in line with the Emergency Response Plan, and that the population around the plant is already evacuated.

About 150 persons from populations around the Daiichi site have received monitoring for radiation levels. The results of measurements on some of these people have been reported and measures to decontaminate 23 of them have been taken. The IAEA will continue to monitor these developments.

Evacuation of the population from the 20 kilometre zone is continuing.

The Japanese have asked that residents out to a 30 km radius to take shelter indoors. Japanese authorities have distributed iodine tablets to the evacuation centres but no decision has yet been taken on their administration.

Background on Radiation

A person’s radiation exposure due to all natural sources amounts on average to about 2.4 millisievert (mSv) per year. A sievert (Sv) is a unit of effective dose of radiation. Depending on geographical location, this figure can vary by several hundred percent.

Since one sievert is a large quantity, radiation doses are typically expressed in millisievert (mSv) or microsievert (µSv), which is one-thousandth or one millionth of a sievert. For example, one chest X-ray will give about 0.1 mSv of radiation dose.

For further information on radiation: http://www.iaea.org/Publications/Factsheets/English/radlife.html

Japanese Earthquake Update (15 March 07:35 UTC)

Japanese authorities have confirmed that the fire at the spent fuel storage pond at the Unit 4 reactor of Fukushima Daiichi nuclear power plant was extinguished on 15 March at 02:00 UTC.

Please note that all future communications from the IAEA regarding events in Japan will use the Coordinated Universal Time (UTC) standard.

The IAEA continues to liaise with the Japanese authorities and is monitoring the situation as it evolves.

Japan Earthquake Update (15 March 2011, 05:15 UTC)

Japanese authorities informed the IAEA that there has been an explosion at the Unit 2 reactor at the Fukushima Daiichi plant. The explosion occurred at around 06:20 on 15 March local Japan time.

Japanese authorities also today informed the IAEA at 04:50 CET that the spent fuel storage pond at the Unit 4 reactor of the Fukushima Daiichi nuclear power plant is on fire and radioactivity is being released directly into the atmosphere.

Dose rates of up to 400 millisievert per hour have been reported at the site. The Japanese authorities are saying that there is a possibility that the fire was caused by a hydrogen explosion.

The IAEA is seeking further information on these developments.

The IAEA continues to liaise with the Japanese authorities and is monitoring the situation as it evolves.

Japan Earthquake Update (15 March 2011, 02:35 UTC)

Japanese authorities yesterday reported to the IAEA at 20:05 UTC that the reactors Units 1, 2 and 3 of the Fukushima Daini nuclear power plant are in cold shutdown status. This means that the pressure of the water coolant is at around atmospheric level and the temperature is below 100 degrees Celsius. Under these conditions, the reactors are considered to be safely under control.

Japanese authorities have also informed the IAEA that teams of experts from Tokyo Electric Power Company (TEPCO), the plant´s operator, are working to restore cooling in the reactor Unit 4 and bring it to cold shutdown.

The IAEA continues to liaise with the Japanese authorities and is monitoring the situation as it evolves.

Source: iaea.org