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

Saturday, April 23, 2011

Saturday afternoon update...

Temperatures and pressures in the three reactor plants suffering accidents at Fukushima Daiichi remain steady, even slightly lowering. This is a good sign - having had this condition last this many days.

However, there are now multiple reports that NISA is questioning the quake resistance of the reactor buildings at Fukushima Daiichi if the dry wells are filled to the level of active fuel. This would be a considerable mass of water; we haven't seen any figures quoted yet, but that much mass that high up in reactor buildings already very seriously damaged is surely something worth thinking about.

TEPCO is clearly thinking about getting the still possibly semi-molten fuel masses covered in the reactors, and with the known leakage in the recirc pump loops the only way to get water level inside the pressure vessel above the level of the inlets of the jet pumps is to raise the level OUTSIDE the pressure vessel above them. Yes, there will be some contact cooling at the lowest radii of the lower pressure vessel head and maybe some along the pressure vessel barrel itself but the primary goal is to raise water level INSIDE the pressure vessel, all the way through and not just in the outer annulus. As we mentioned before, there is probably no direct flow through the cores at all if only the normal feed lines are in use; TEPCO either needs to send water through the spray nozzles / spargers or else fill the dry wells; it's that simple.

This presents a very ugly catch 22 situation. Further, there are structural integrity questions now about the spent fuel pool in No. 4 plant, already mentioned on this blog, and so we find the situation now that in order to do what it must -- cool the reactor cores, and cool the spent fuel pool in No. 4 plant -- TEPCO must risk structural failure in one building and seriously reduced earthquake resistance due to higher level, or altitude if you will, water mass in the others.

Perhaps the biggest news of the day is the discovery on-site of a chunk of building material that is reading 90 R/Hr. This is a pretty hot piece of building material; it's been taken away and stored. One wonders just how this chunk got this hot .. where did the contamination come from, and where inside the reactor buildings will they find the area where it used to be? Will that area be just as bad, as a whole zone or rad field? This piece was found by No. 3 reactor building. Surely TEPCO will try to quickly analyze this thing to find out what's on/in it.

More details as they come out.. but it's Saturday, and news is fairly quiet in Japan on weekends, it seems.

3:45 PM Eastern Saturday 4/23
ATOMIC POWER REVIEW

2 comments:

  1. Shortly after the reactor 3 explosion, when the initial clean up efforts began, there was mention of a piece of highly contaminated debris found between reactors 3 and 4.
    There was no specific quantitative radioactivity assessment made public at the time, but it may be a related piece of material.
    Separately, a cleanup that is so difficult that it generates one container/day is inherently protracted.
    It seems that this effort will consume the professional lifetimes of many of the people involved.
    I wonder whether they are on board with that.

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  2. Possibly a hunk of the #3 shield plug?

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