APR: your source for nuclear news and analysis since April 16, 2010

Tuesday, April 12, 2011

Fukushima Daiichi developments... Tuesday evening

The press is reporting a number of developments, very widely, so I'll just echo them here with some analysis.

TEPCO continues to move water around.... TEPCO is in the initial phases of dewatering the No. 2 plant's turbine building and pipe tunnel to restore as normal shutdown cooling as is possible given the situation. This plant has the most highly contaminated water of any of the sites, both in its turbine building and in its outside service water pipe tunnel. It's interesting to note the revelation of the spike in aerial activity that correlates with the drywell or suppression pool integrity failure on this plant and to also note the very high level of contamination found in abnormal areas in this plant. We'll look carefully through the data that have been revealed to see whether this is simply due to a lack of water in the suppression pool to scrub contamination from venting of the plant, or if perhaps the containment was vented to the turbine building as an emergency measure.

TEPCO high-purity nitrogen injection to unit No. 1 continues... Even though TEPCO has been putting nitrogen into the drywell on No. 1 plant, the pressure is not increasing as much as they think it should be due to this. That is making TEPCO think that they've lost integrity on this drywell as well, perhaps not as badly as at No. 2 but enough to allow a stabilization of pressure right around 30 psia. Many studies have speculated about primary containment failure modes, but one has to wonder if the collapse of the top part of the reactor building.. which should include a refueling crane somewhere.. has not damaged the drywell head. On this plant, it does appear that much of the upper structure dropped straight down instead of being blown all over the area as in the example of No. 3 plant.

Apparently most of the problematic water at No. 5 and No. 6 plants has been disposed of. The latest photo of the Fukushima Daiichi site shows the barge with the crane on it back in action near the inlet area for Nos. 1 through 4 plants.

9:52 PM Eastern Tuesday 4/12

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