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Monday, March 28, 2011

Fukushima Nuclear Accident Update Log (Updates of 27 March 2011)

From IAEA :

" IAEA Briefing on Fukushima Nuclear Accident (27 March 2011, 13:30 UTC)

1. Current Situation

The situation at the Fukushima Daiichi plant remains very serious. The restoration of off-site power continues and lighting is now available in the central control rooms of Units 1, 2 and 3.

Also, fresh water is now being injected into the Reactor Pressure Vessels (RPVs) of all three Units. Radiation measurements in the containment vessels and suppression chambers of Units 1, 2 and 3 continued to decrease. White "smoke" continued to be emitted from Units 1 to 4.

Pressure in the RPV showed a slight increase at Unit 1 and was stable at Units 2 and 3, possibly indicating that there has been no major breach in the pressure vessels. At Unit 1, the temperature measured at the bottom of the RPV fell slightly to 142 °C. At Unit 2, the temperature at the bottom of the RPV fell to 97 °C from 100 °C reported in the Update provided yesterday.

Pumping of water from the turbine hall basement to the condenser is in progress with a view to allowing power restoration activities to continue. At Unit 3, plans are being made to pump water from the turbine building to the main condenser but the method has not yet been decided.

This should reduce the radiation levels in the turbine building and reduce the risk of contamination of workers in the turbine building restoring equipment. No notable change has been reported in the condition of Unit 4. Water is still being added to the spent fuel pools of Units 1 to 4 and efforts continue to restore normal cooling functions. Units 5 and 6 remain in cold shutdown. We understand that three workers who suffered contamination are still under observation in hospital.

2. Radiation Monitoring

Dose rates at the Fukushima site continue to trend downwards. In 28 of the 45 prefectures for which data are available, no deposition of radionuclides was detected in the period 18 to 25 March. In seven of the other 17 prefectures, the estimated daily deposition was less than 500 becquerel per square metre for iodine-131 and less that 100 becquerel per square metre for caesium-137.

On 26 March, the highest values were observed in the prefecture of Yamagata: 7 500 becquerel per square metre for iodine-131 and 1200 becquerel per square metre for caesium-137. In the other prefectures where deposition of iodine-131 was reported, the daily range was from 28 to 860 becquerel per square metre. For caesium-137, the range was from 2.5 to 86 becquerel per square metre."

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