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

Thursday, May 12, 2011

Fukushima Daiichi No. 1 - estimates worsen

TEPCO has now reported, through a management rep speaking at a press conference, a number of new things about Fukushima Daiichi No. 1.

-There are some welded pipe failures, amounting to a total leak area of several centimeters, now known to exist at No. 1 plant. The exact systems and locations have not been revealed. This is one source of outflow from the reactor vessel.

-There may be failures of the lower pressure vessel head. This would be a second source for outflow.

-It appears that the entire active fuel region of the core, when in normal condition, is exposed .. i.e. not covered with water. It may not have been since nearly the start of the casualty.

-Some of the fuel has very likely melted and dropped into the lower pressure vessel head area. BWR reactors, because of their power profile, would be expected to experience fuel element melt from the center outward over a span of time without cooling. TEPCO has not given a clue as to how much of the fuel is damaged, but we noted the reduction a few weeks ago in the estimated percentage from 70% down to 55% and wonder if this won't get moved back up. Perhaps higher.

Again, the exact location of the mentioned pipe holes is not known. The lower pressure vessel head failures may be one and the same... i.e. welded pipe penetrations in this lower head or the core barrel near the head flange. CRDM drive tubes are also likely candidates if a molten fuel pour occurred.

Speculation is now wide in the media and among knowledgeable persons that TEPCO will not meet its previously stated timeline for recovery.

...What is surprising to this author is the apparent surprise among some other supposedly knowledgeable people that the water in the turbine buildings has been coming all along from the feed and bleed cooling of the reactors. Today I have seen at least two stories in big media where purported nuclear engineers are quoted as saying that "there is raised the possibility that this water is coming from the reactor buildings, having come from the reactors themselves" or some such. This is not a surprise, has been the case all along, has been the cause of all of the highly contaminated water found on site and in the ocean and frankly anyone acting surprised about this now should be embarrassed.

We will post more details when they're available.

1:00 PM Eastern Thursday 5/12
ATOMIC POWER REVIEW

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