18 Mar (NucNet): Radiation levels on the site and at the site boundary of the Fukushima-Daiichi nuclear power plant in Japan are slowly falling, but are still far above normal levels, according to figures from Tokyo Electric Power Company (Tepco) and Japan’s Nuclear and Industrial Safety Agency (NISA).
At a monitoring post near one of the gates, readings have fallen from 310 microsieverts per hour (microSv/hr) yesterday to 264 microSv/hr (at 12:00 Japan time on 18 March), they said.
Readings from a mobile monitoring post on the plant site have not been updated today, but final readings from yesterday (17 March) at 20:00 Japan time showed 3,600 microSv/hr.
In most countries, the natural background radiation level is in the range of 0.2 to 0.5 microSv/hr, including the natural radon background radiation in buildings.
Unit Status: 18 March 06:00 Japan Time
Unit 1: Cooling with seawater continues.
Unit 2: Cooling with seawater continues. White smoke has been discharged from the reactor building, where damage is suspected to the containment vessel. The cause of the smoke has not been confirmed.
Unit 3: Cooling with seawater continues. After dropping water four times from helicopters yesterday, five tanks of water have been injected from the ground to the spent fuel pool sector using a water-cannon truck. The results are being evaluated.
Unit 4: Work continues to stabilise the reactor, which was shut down at the time of the earthquake and has no fuel in it. Work also continues to stabilise the spent fuel pool, which is almost full of spent fuel. The plan is to fill this pool with cooling water from water cannon and from the unit’s normal pumps as soon as power is re-established onsite. The International Atomic Energy Agency (IAEA) said the temperature of the spent fuel at unit 4 was 84 degrees Celsius on 14 March at 04:08 Japan time. There are no newer readings.
Units 5 and 6: The status of these reactors and of their fuel pools remains stable as long as the emergency power diesel engine for unit 6 – the only one that is working – remains operational and supplies power to the pool cooling system and essential water cooling components. Tepco said it hopes the situation can be improved with restoration of the plant’s main external power supply. The IAEA said the temperature of the fuel in the unit 5 fuel pool was 65.5 degrees Celsius at 03:00 Japan time on 18 March. At unit 6 it was 62 degrees Celsius.
External power supply: A connection has been laid from the Tohoku high-voltage line to the site and at 06:30 Japan time today it was being checked. Final connection must wait until water injection can be interrupted. The IAEA said engineers had also begun to lay an external grid power line cable to unit 2 at the plant. The operation was continuing as of 05:30 Japan time. They plan to reconnect power to unit 2 once the spraying of water on the unit 3 reactor building is completed.
The latest status update from the Japan Atomic Industrial Forum is online:
http://www.jaif.or.jp/english/
>>Related reports in the NucNet database (available to subscribers)
Authorities Order Evacuation Around Fukushima-Daiichi Nuclear Plant (News in Brief No. 52, 11 March 2011)
EC Calls For Information On Back-Up Power Systems At European NPPs (News In Brief No. 66, 15 March 2011)
Japan Releases Radiation Data From More Than 50 Monitoring Posts (News in Brief No. 71, 17 March 2011)
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