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

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  •  And? (1+ / 0-)
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    Joy Busey

    You think that having a reactor that is only a couple faulty pipes away from explosion warrants no containment structure?  In nuclear reactor design, you have to count on things failing in the worst possible way.  Look at MONJU for an example of that.  They never expected sodium to leak and took great care to prevent leaks, but just in case, they clad the concrete in steel, since their calculations showed the sodium wouldn't eat through the steel, get to the concrete, and cause an explosion.  And still, an instability in the flow did rupture a pipe, did leak out huge amounts of sodium, and the sodium did eat halfway through the cladding.  Utter disaster.  Have you seen the video?  Looks like something out of a horror movie.

    But hey.... "containment structure."
    Which is why PBMRs scare the heck out of me.  "No Containment Structure = No Go" in my book.

    •  They don't use (0+ / 0-)

      sodium, do they? In fact, what IS there to leak? The pebbles rolling down a driveway? There is no liquid in them at all. Just inert helium. I am actually for them building some sort of containment structure. Not because they need them...they don't, but to end the discussion. Also, since it built underground, building containment (beyond the Containment they actually ARE built with) would be very cheap and probably mass produced.

      As it happens the NRC is working with the S. African company prior them submitting a design certification to the NRC for approval.


      •  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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