Positive developments at Japanese nuclear reactors but still serious

(crikey.com.au)The International Atomic Energy Agency believes there have been some positive developments in the last 24 hours, but the overall situation at the Fukushima Daiichi nuclear power plant remains very serious. The latest IAEA Briefing on the Emergency (20 March 2011, 15.30 UTC) said radiation levels in major Japanese cities have not changed significantly since yesterday and remain below those which are dangerous to human health.

Graham Andrew, Special Adviser to the IAEA Director General on Scientific and Technical Affairs reported:

1. Current Situation

There have been some positive developments in the last 24 hours, but the overall situation at the Fukushima Daiichi nuclear power plant remains very serious.

Efforts to restore electrical power to the site continue. Off-site electrical power has been connected to the local substation for Unit 2 today. Work is continuing under difficult conditions to connect power from the substation to the reactor building. Seawater is still being injected into the reactor pressure vessels of Units 1, 2 and 3.Water injection is not needed for Unit 4 as the reactor is in outage.

White smoke or vapour from Unit 3 is still being observed, but it is less intense than on previous days. Spraying of the reactor building with water is in progress. Following an initial rise in pressure in the Unit 3 reactor pressure vessel, plans were made to vent the vessel should it become necessary. However, from information recently provided by NISA they have decided not to vent as the vessel pressure has started to reduce.

The situation in the reactor spent fuel pools is relatively stable, but is still of concern. Spraying of water into the pool of Unit 4 started yesterday. The Agency still lacks data on water levels and temperatures at the spent fuel pools at Units 1, 2, 3 and 4.

A positive development is that cooling has been restored to the reactor pressure vessels in Units 5 and 6. Temperatures in the spent fuel pools at these two units, which had been rising in the last few days, have now fallen significantly to around 40 degrees centigrade from a maximum of about 69 degrees yesterday. Two diesel generators, one for each Unit, are providing electricity.

2. Radiation Monitoring

Radiation levels in major Japanese cities have not changed significantly since yesterday and remain below those which are dangerous to human health.

The IAEA radiation monitoring team took additional measurements yesterday between Tokyo and locations up to 150 km from the Fukushima site. Dose rates were typically a few microsieverts per hour compared to a typical background level of around 0.1 microsieverts per hour.

From the measurements taken within the exclusion zone, no significant alpha radiation has been detected so far.

This morning, we received additional data from the Agency’s monitoring team which indicated contamination on the ground at a location 50 to 70 km from the Fukushima site. The team will make confirmatory measurements tomorrow at the same locations to help validate the initial results. Grass and other samples have also been taken by the team from various locations in the Fukushima Prefecture for analysis. In the coming days, the IAEA monitoring team plans to take measurements at the same locations monitored by the Japanese authorities. This will assist in the validation of measurements. The IAEA is sending additional monitoring experts to Japan to supplement its capabilities in the field.

Some results on the monitoring of foodstuffs have been made available by Japan to the IAEA and FAO. We can confirm measurements indicating that, in some areas, Iodine-131 in milk and in freshly grown leafy vegetables, such as spinach and spring onions, is significantly above the levels set by Japan for restricting consumption of these food products.

 

Source: http://blogs.crikey.com.au/thestump/2011/03/21/positive-developments-at-japanese-nuclear-reactors-but-still-serious/

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