Japan’s Reactors Still ‘Not Stable,’ U.S. Regulator Says

[jpak]

http://www.nytimes.com/2011/04/13/world/asia/13safety.html?partner=rss&emc=rss

The condition of the damaged Fukushima Daiichi reactors in Japan is “static,” but with improvised cooling efforts they are “not stable,” the chairman of the Nuclear Regulatory Commission told a Senate committee on Tuesday.
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“We don’t see significant changes from day to day,” the chairman, Gregory B. Jaczko, said, while adding that the risk of big additional releases gets smaller as each day passes.

Long-term regular cooling of the reactors has not been re-established, nor has a regular way of delivering water to the spent-fuel pools, he told the Senate Environment and Public Works Committee. And when an aftershock hit the site and cut some offshore power supplies, he said, some pumps failed and cooling stopped for 50 minutes.

The situation is “not stable” and will remain so until “that kind of situation would be handled in a predictable manner,” he said. Mr. Jaczko also offered a new theory about the cause of the explosions that destroyed the secondary containment structures of several of the reactors. The prevailing theory has been that hydrogen gas was created when the reactor cores overheated and filled with steam instead of water; the steam reacts with the metal, which turns into a powder and then gives off hydrogen.

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[Marblehead]

1. Worse and getting worser

This could go on for months,years.

[Javaman]

3. The effects will be with us for years. nt

[FBaggins]

2. The second point in an interesting one.

Sure, they're not "stable", but there's nothing new there. They won't be stable for months.

The theory on the explosions is worth discussing however.

He's essentially speculating that the hydrogen gas came from the spent fuel pools rather than from the cores. I have a tough time thinking that's likely. Yes, fuel pools do give off some hydrogen and they have to be vented carefully to minimize risk of an explosion. Obviously a loss of power means that this ventalation (and the sensors that detect hydrogen building up) wouldn't be working. It also means that the pools would be slowly heating up and would give off more hydrogen as that happened. But having said all that, the first explosion was awfully early in the timeline to think that it might be just that minimal hydrogen generation... but it was very close (in time) to the venting operations from the core that was overheating much more rapidly.