BNC{ Fukushima Daiichi Open and Update Thread #5 Barry Brook | 23 April 2011 at 1:58 AM

Fukushima Daiichi Open and Update Thread #5 Barry Brook | 23 April 2011 at 1:58 AM | Categories: Nuclear, Open Thread | URL: http://wp.me/piCIJ-1ac

The problems at the Fukushima Daiichi nuclear power plant continue to be worked on, with no short-term resolution in sight. Here are eight recent notable happenings, compiled from various sources (see list below):
1. Reports indicate that some fuel melted and fell to the lower containment sections of units 1-3, where it dispersed in a fairly uniform residue -- but this does not seem to have breached containment in any of the reactor pressure vessels. Re-criticality of this 'corium' seems very unlikely, but no details can of course be confirmed until the reactor cores are finally dismantled -- which may be years away.
2. Two automated PackBot robots entered units 1 and 3, took photos, and measured temperature, pressure and radioactivity within the buildings. Peak levels were 40-60 mSv/hr.

3. An anti-scattering agent is being sprayed on the ground around the damaged units (about 1,200 square metres in area) to prevent further spread of radionuclides (see photo above).
4. Excess radioactive cooling water continues to be transferred from unit 2's basement and tunnels to a waste processing facility.
5. Further surveys are being made of the area surrounding the Fukushima evacuation zone and the exclusion area is being policed more strictly. Highest levels were measured at Itate, at about 4 microsieverts per hour (by comparison, the background level is 0.2 -- 0.4  uSv/hr).
6. TEPCO have now released a roadmap plan for the restoration of stable conditions at the site, over a 3 -- 6 month timetable, leading to a cold shutdown at units 1-3 and various other stability targets. They also released a 27-slide presentation on the timeline of the accident and current situation, that is definitely worth a look through.
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