IAEA Briefing on Fukushima Nuclear Accident (30 March 2011, 16.30 UTC)
On Wednesday, 30 March 2011, the IAEA provided the following information on the current status of nuclear safety in Japan.1. Current Situation
Overall at the Fukushima Daiichi plant, the situation remains very serious.
With respect to the water that is present in the turbine buildings. In Unit 1, water has continued to be pumped into the condenser with 3 pumps (6.5 ton/hour each) and the water level has reduced from 40cm to 20cm. In Unit 2 from 07.45 UTC, pumping of water from the Condensate Storage Tank into the Surge Tank was started so that the that condenser can be drained to the Condensate Storage Tank and contaminated water can be pumped out from the Turbine building into the condenser. The same process of pumping the water from the Condensed Water Storage Tank into the Surge Tank was started on Unit 3 at 08.40 UTCon March 28.
Near the Unit 3 building, 3 workers spilled water over themselves when removing a flange from seawater pipes on the residual heat removal system (RHR). After showering, contamination was not detected.
Fresh water has been continuously injected into the Reactor Pressure Vessel (RPV) through feed-water line at an indicated flow rate of 8.0 m3/h at Unit 1. The pumping of freshwater into the RPV has been switched from fire trucks to temporary electrical pumps with diesel generator. At Units 2 and 3 fresh water is being injected continuously through the fire extinguisher line at an indicated rate of 7 m3/h using a temporary electric pump.
The indicated temperature at the feed water nozzle of the RPV of Unit 1 has decreased from 323 oC to 281 oC and at the bottom of RPV remained stable at 134 oC. There is a corresponding decrease in Drywell pressure. At Unit 2 the indicated temperature at the feed water nozzle of the RPV has increased from 154 oC to 177 oC and at the bottom of RPV has increased from 78 oC to 88 oC. Indicated Drywell pressure remains at atmospheric pressure. For Unit 3 the indicated temperature at the feed water nozzle of the RPV is about 75 oC and at the bottom of RPV is about 116 oC. The validity of the RPV temperature measurement at the feed water nozzle is still under investigation.
With respect to the Spent Fuel Pools. It was planned to commence the pumping of water into the Unit 1 Spent Fuel Pool by concrete pumping truck from 29 March. Also on 29 March pumping of fresh water into the Unit 2 spent fuel pool commenced via a temporary electrical pump. The temperature of the spent fuel pool is 46o C as of 19:00 UTC 29 March. For Unit 4 it was planned to commence pumping freshwater into the spent fuel pool on March 29. The IAEA has not received information on implementation of spraying activities in units 1 and 4.
Units 5 and 6 remain in cold shutdown
2. Radiation Monitoring
The majority of the recently measured radioactivity levels in drinking water are being reported below the levels established by the Japanese authorities which are 100 Bq/L of I-131 for infants; 300 Bq/L for adults and 200 Bq/L of Cs-137 for infants and adults. Previously imposed recommendations for restrictions on drinking water are being lifted in most of the affected locations. As of 28 March, recommendations for restrictions based on I-131 concentration remain in place in one village in the Fukushima prefecture. In three other locations of the Fukushima prefectures, restrictions continue to apply for infants only.
Two IAEA teams are currently monitoring radiation levels and radioactivity in the environment in Japan. On 29 March, one team made gamma dose-rate measurements in the Tokyo region at 8 locations. Gamma-dose rates measured ranged from 0.02 to 0.19 microsievert per hour, which is within or slightly above the background.
The second team made additional measurements at distances of 32 to 62 km, at directions North to Northwest from the Fukushima nuclear power plant. At these locations, the dose rates ranged from 0.5 to 6.8 microsievert per hour. At the same locations, results of beta-gamma contamination measurements ranged from 0.05 to 0.45 Megabecquerel per square metre.
Based on measurements of I-131 and Cs-137 in soil, sampled from 18 to 26 March in 9 municipalities at distances of 25 to 58 km from the Fukushima Nuclear Power Plant, the total deposition of iodine-131 and cesium-137 has been calculated. The results indicate a pronounced spatial variability of the total deposition of iodine-131 and cesium-137. The average total deposition determined at these locations for iodine-131 range from 0.2 to 25 Megabecquerel per square metre and for cesium-137 from 0.02-3.7 Megabecquerel per square metre. The highest values were found in a relatively small area in the Northwest from the Fukushima Nuclear Power Plant. First assessment indicates that one of the IAEA operational criteria for evacuation is exceeded in Iitate village. We advised the counterpart to carefully access the situation. They indicated that they are already assessing.
As far as food contamination is concerned, 35 samples taken from 25-29 March, and reported on 29 March, for various vegetables, fruit (strawberry), seafood, pork and unprocessed raw milk in nine prefectures (Chiba, Gunma, Ibaraki, Kanagawa, Nagano, Niigata, Saitama, Tochigi and Yamagata), stated that results for iodine-131, caesium-134 and caesium-137 were either not detected or were below the regulation values set by the Japanese authorities.
The Joint FAO/IAEA Food Safety Assessment Team met with local government officials in Tochigi prefecture on 29th March and provided advice related to contamination of food and the environment.
Local government officials briefed the FAO/IAEA Team on the extent of contamination in Tochigi, the principle agricultural products affected, the main production areas and production methods (greenhouses, open-air), levels of contamination found (principally in air, tap/ground water and vegetables) and imminent plans to monitor soil contamination. A field visit also took place to a spinach producer outside Utsanomiya City.
Based on these latest discussions with the Tochigi authorities, it is apparent that the focus of the Joint FAO/IAEA mission has changed to some extent from the mechanisms of contamination to remediation strategies and techniques related to plant and animal production, food traceability and water/soil characterization.
The FAO/IAEA team is also meeting with the local government officials in Gunma prefecture today.
No new results from the marine monitoring stations 30 km off-shore as well as from close to the discharge, were reported since 27 March.
One IAEA staff member of the Monaco marine laboratory will fly to Japan on 31 March in order to join the Japanese team assessing marine environment.
The IAEA continues activities under the Joint Radiation Emergency Management Plan of the International Organisations through regular video/teleconferences. As of March 30 the WHO liaison officer is working in the IEC.
In response to the request for data on measurement, the IEC has received information from Singapore. The Singapore Authorities have sent reports on measurements in food imported from Japan (cabbages). Some samples were over the Codex Alimentarius values recommended for international trade. In Singapore no increase in gamma dose rates have been observed and no fission products have been found in air samples.
No comments:
Post a Comment