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View Diary: New Nukes: Obama will name Steven Chu his choice for Energy secretary (124 comments)

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  •  MONJU was not a PBMR (0+ / 0-)

    Just an example of an example of unexpected escalation in a nuclear reactor.  There weren't supposed to be flow instabilities.  There weren't supposed to be leaks.  The leaked sodium wasn't supposed to be able to eat through steel plating.  All of those things happened, one after another.

    As for PBMRs, there is liquid in many, if not most designs -- as an extra coolant loop, for hydrogen generation, or whatnot.  Not that you need liquid -- see the Hamm-Uentrop incident in 1986 for an example even in the very brief history of pebble beds.  And in all, in the event of primary loop failure, it is presumed that air will safely cool the pebbles -- oxygen + hot graphite simply is not a safe situation.  The reason that they don't build containment structures is that PBMRs don't produce much power, so they can't afford it.

    PBMRs are not built with containment structures.  They're built with confinement structures, which are completely different.  Chernobyl didn't have a containment structure; it had a confinement structure.  In this context, "confinement structure" means little more than "walls around a reactor and a filtered vent in the roof" -- not blast-resistant positive-pressure environment.

    I'm hardly the only one who thinks that there's not nearly enough margin of safety without a containment structure, I should add.  Read Moormann's work, for example.  This tech is anything but mature, and yet they want us to treat it as foolproof.

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