Nuclear officials confirm hydrogen explosion at Unit 3 of Fukushima Dai-ichi plant

[jpak]

http://www.washingtonpost.com/world/nuclear-officials-confirm-hydrogen-explosion-at-unit-3-of-fukushima-dai-ichi-plant/2011/03/13/ABPCpIU_story.html

[FBaggins]

1. I'd say that we have a statistically significant dataset at this point.

Of the reactors that were hit hardest by the earthquake and flooded by the tsunami, there seems to be a fairly similar path that these BWRs take (with some notable variations). A few different, but related designs... similar results.

[kristopher]

2. Update from Union of Concerned Scientists (pre-explosion discussion of containment failure)

...I have done considerable analysis on the safety risks associated with using MOX fuel in light-water reactors. The use of MOX generally increases the consequences of severe accidents in which large amounts of radioactive gas and aerosol are released compared to the same accident in a reactor using non-MOX fuel, because MOX fuel contains greater amounts of plutonium and other actinides, such as americium and curium, which have high radio-toxicities.

Because of this, the number of latent cancer fatalities resulting from an accident could increase by as much as a factor of five for a full core of MOX fuel compared to the same accident with no MOX. Fortunately, as noted above, the fraction of the fuel in this reactor that is MOX is small. Even so, I would estimate this could cause a roughly 10% increase in latent cancer fatalities if there were a severe accident with core melt and containment breach, which has not happened at this point and hopefully will not.

While the authorities continue playing down the possibility of a breach of the primary containment at these reactors, I remain concerned. Fukushima Dai-Ichi reactor Units 1, 2, and 3 are boiling water reactors with Mark I containments. The Mark I is unusually vulnerable to containment failure in the event of a core-melt accident. A recent study by Sandia National Laboratories shows that the likelihood of containment failure in this case is nearly 42% (see Table 4-7 on page 97). The most likely failure scenario involves the molten fuel burning through the reactor vessel, spilling onto the containment floor, and spreading until it contacts and breeches the steel containment-vessel wall.

The Sandia report characterizes these probabilities as “quite high.” It’s not straightforward to interpret these results in the context of the very complicated and uncertain situation at Fukushima. But they are a clear indication of a worrisome vulnerability of the Mark I containment should the core completely melt and escape the reactor vessel.

http://allthingsnuclear.org/tagged/Japan_nuclear?utm_source=SP&utm_medium=more&utm_campaign=sp-nuke-more-3%2F13%2F2011-pm

[kristopher]

3. Wish we could see what the hell is going on in there. nt