Weekly IAEA update on Fukushima

A weekly update from IAEA.org on the Fukushima Daiichi accident.

Fukushima Nuclear Accident Update (3 April 2011, 17:15 UTC)
Japanese authorities today informed the IAEA of the following developments at the Fukushima Daiichi nuclear power plant:

In Units 1, 2 and 3, external power supply is now being used to power the pumps that are injecting fresh water into the reactors, thus replacing temporary electrical pumps.

The switch to external power supply occurred on 3 April at:

03:02 UTC (12:02 Japan time) for Unit 1.
03:12 UTC (12:12 Japan time) for Unit 2.
03:18 UTC (12:18 Japan time) for Unit 3.

Some lighting has been reactivated in the turbine buildings of Units 1, 2, 3 and 4.

IAEA Briefing on Fukushima Nuclear Accident (3 April 2011, 12:00 UTC)
? Summary of Reactor Status

On Sunday, 3 April 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.

On 2 April, transferring of water from the Unit 1 condenser storage tank to the surge tank of the suppression pool was completed in preparation for transferring water in the basement of the Unit 1 turbine building to the condenser. Also, on 2 April transferring of water from the Unit 2 condenser storage tank to the surge tank of the suppression pool was started in preparation for transferring water in the basement of the Unit 1 turbine building to the condenser.

A second US Navy barge arrived on 2 April carrying fresh water to be transferred to the “filtered water tank”.

TEPCO has identified a possible leakage path from the Turbine building of Unit 2 to the sea via a series of trenches/tunnels used to provide power to the sea water intake pumps and supply of service water to the reactor and turbine buildings. As of 2 April, 07:25 UTC, the pouring of concrete was started in an attempt to stop the water leakage. As of 2 April, 10:15 UTC, pouring of concrete had ceased and no significant decrease in the rate of leakage was observed. There is a plan to inject polymer to attempt to stop the leakage. TEPCO announced on 2 April that, following the detection of highly contaminated water leaking through a crack found in a pit near Unit 2, they had added 3 additional sampling points at 15 km from Fukushima Daiichi and Fukushima Daiini.

Fresh water has been continuously injected into the Reactor Pressure Vessel (RPV) of Unit 1 through the feed-water line at an indicated flow rate of 8 m3/h using a temporary electric pump with diesel backup. Fresh water is being injected continuously into the RPVs in Units 2 and 3 at indicated rates of 9 m3/h and 7 m3/h respectively through the fire extinguisher lines using temporary electric pumps with diesel backup.

In Unit 1 the indicated temperature at the feed water nozzle of the RPV is relatively stable at 259 °C and at the bottom of RPV at 117 °C. The RPV pressure indications are fluctuating and Drywell pressure is slightly decreasing. In Unit 2 the indicated temperature at the feed water nozzle of the RPV has decreased slightly from 161 °C to 153 °C. The temperature at the bottom of RPV was not reported. Indicated Drywell pressure remains at atmospheric pressure. The indicated temperature at the feed water nozzle of the RPV in Unit 3 is stable at 118 °C and at the bottom of the RPV is about 92 °C. The validity of the RPV temperature measurement at the feed water nozzle is still under investigation.

Injection of water into the spent fuel pool in Unit 2 using the temporary pump was restarted on 1 April.

Units 5 and 6

Both units remain in cold shutdown with plant systems operating on off-site AC power.

Common Spent Fuel Storage Facility

The Common Spent Fuel Pool temperature is stable. TEPCO tested an “anti-scattering” agent (2 000 l) on 500 m2 area around the Common Spent Fuel Storage facility on 1t April. The purpose of spraying is to prevent radioactive particles from being dispersed from the plant by winds and rain.

2. Radiation Monitoring

On 2 April, deposition of iodine-131 was detected in 7 prefectures ranging from 4 to 95 becquerel per square metre. Deposition of cesium-137 in 6 prefectures was reported on 2 April ranging from 15 to 47 becquerel per square metre. Reported gamma dose rates in the 45 prefectures showed no significant changes compared to yesterday.

Most of the previously imposed recommendations for restrictions on drinking water have been lifted. As of 2 April, one recommendation for the restriction based on iodine-131 concentration was in place in one village in the Fukushima prefecture, which applied for infants only. Meanwhile, also in this village, the iodine-131 level in drinking water has dropped below 100 becquerel per litre, which is the recommended restriction level for intake by infants. The restriction is still in place as a precautionary measure of the local authority.

Currently, one IAEA monitoring team is working in the Fukushima region. On 2 April, measurements were made at 7 locations at distances of 32 to 62 km, North and Northwest to the Fukushima nuclear power plant. The dose rates ranged from 0.6 to 4.5 microsievert per hour. At the same locations, results of beta-gamma contamination measurements ranged from 0.09 to 0.46 megabecquerel per square metre.

3. BWR Experts

The two agency experts in BWR technology have arrived in Japan. The objective of this expert visit is to have a direct exchange of views with the Japanese counterparts.

4. TEPCO Employees

TEPCO had been investigating two employees who had been missing since the earthquake of 11 March. On 2 April NISA reported that on the afternoon of 30 March the two employees were found dead in the -1 Level of the Turbine Building of Unit 4.

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