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View Diary: Big Trouble In Arkansas w/Update (246 comments)

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    •  Well, I don't know. (9+ / 0-)

      To deliver a credible opinion on this topic, ultimately, it seems you'd need to be a nuclear physicist or engineer, one with the most humanist and progressive qualifications.

      Part of what makes arguments about nuclear power so troubling, is how little average people understand about it.

      It's here they got the range/ and the machinery for change/ and it's here they got the spiritual thirst. --Leonard Cohen

      by karmsy on Wed Apr 03, 2013 at 03:57:30 PM PDT

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    •  France is closest (4+ / 0-)

      Of course, they do "reprocessing" which is the devil's work if you ask me (snark) :)

      But spent fuel is not the biggest issue - it's water and waste heat:

      Make sure everyone's vote counts: Verified Voting

      by sacrelicious on Wed Apr 03, 2013 at 04:47:58 PM PDT

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    •  Even if it can't be solved completely (1+ / 0-)
      Recommended by:

      the quantity of waste (& the amount of time it needs to be safely sequestered) can in theory be reduced to the point where the problem is tractable. Not only that, but the same technology appears to be inherently safe from Fukushima/Chernobyl/TMI catastrophic failure, highly proliferation resistant, and very efficient in the use of fuel.

      I'm thinking of a molten-salt reactor, where the fuel circulates continuously through the reactor core at 600 C or so, with a built-in reprocessing loop using thermal separation methods. Molten salt reactors were built and run at Oak Ridge in the 1950s and early 1960s; thermal separation based on boiling/melting points of the various salts is fairly straightforward physical chemistry.

      It looks as if you could configure a reactor of this type as a "transuranic pig" that could gobble up the waste of a current commercial light-water reactor (LWR) & keep circulating it through its innards until almost all of it was digested.

      Some folks are working on these designs, but there's not much funding--the government seems sublimely uninterested. I would imagine part of that comes from the general distrust of nukes (which unfortunately visits the sins of the LWR upon the MSR). But I think the real reason for the inaction is that the contemporary nuclear industry makes its money from the fabrication of solid-fuel elements--which an MSR doesn't need & can't even use.


      by Uncle Cosmo on Wed Apr 03, 2013 at 06:00:00 PM PDT

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      •  any leaks in a MSR (1+ / 0-)
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        you have real issues

        •  And those "real issues" are, at worst, (0+ / 0-)

          that you have a pool of very radioactive fluoride salts that spills onto the floor of the reactor. (In fact the plant would probably be designed to drain all spillage into a highly over-designed holding tank where it would solidify.) Where it sits, patiently cooling down (in both thermal & radioactive senses) while you apply remediation procedures that I would guess have been & are being worked up.

          What you don't have is an explosion to blow the top off the plant & spew radioisotopes into the enviroment. No steam explosion because the MSR doesn't use pressurized water. No hydrogen explosion--caused in the LWR when heat dissociates water into hydrogen & oxygen that then explosively recombine--because the MSR doesn't use water at all.

          There's minimal release of radioactivity because the salts never come close to boiling point (~1400 C) & with no explosion to crack a modest containment vessel (designed to hold 2-3 atmospheres), the small amount of gaseous fission products (which the reprocessing loop has been extracting from the fuel stream anyway, because they tend to inhibit the reaction) don't go anywhere. (In fact you can probably just leave them in the containment & wait a couple of hours --xenon-137 has a halflife of 3.8 minutes and krypton-90 a halflife of 32 seconds--& then deal with non-gaseous daughter products.)

          Meantime, once the fuel pumps are shut off, the reactor stops. It doesn't matter how much fuel has spilled--once it's away from the neutron moderator (on the floor or in a holding tank) the chain reaction can't be sustained. (The designs I've seen incorporate drain plugs in the fuel lines that melt if the reactor ever overheats & send the fuel into a holding tank where--again removed from the moderator--the reaction shuts down.)

          There are a lot of passive safety features inherent to the MSR design & operation which make the chances of catastrophes like TMI, Chernobyl & Fukushima almost zero.


          by Uncle Cosmo on Thu Apr 04, 2013 at 08:36:45 AM PDT

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          •  the idea of a nuclear reactor (0+ / 0-)

            being passively safe is probably overblown at best.

            a serious melt out, with liquid fuel and salt all over the basement will generate steam explosions, as water hits it.

            I'm not real up to speed on MSRs but, i imagine you have a big 1400C Molten salt low pressure primary loop and a big high pressure secondary steam loop you use the secondary to turn the turbines,  and then you have a tertiary cooling tower loop.

            So, suppose you have a crack in the heat exchanger, you still get a steam explosion inside the heat exchanger.

            or suppose you have an earth quake and some pipes bust, you get a steam explosion  then you have molten radioactive salt getting blown around.

            They tried Liquid sodium reactors in the 60's it was a disaster.

            •  I'll have to argue with you here (0+ / 0-)

              Projected operating temperatures are ~700 C to keep the fuel molten--IIRC the salts melt at various points near 400 C and boil around 1400 C.

              Secondary loop would not be steam at those temperatures. One idea I've seen floated is helium running a triple-reheat closed-cycle turbine at 700 C, with an electrical conversion efficiency 50-100% higher than the steam cycle due to the higher temperature. Helium isn't easy to keep confined, but it doesn't become radioactive under neutron bombardment & isn't hazardous unless you try to breathe it without enough oxygen in the mix.*

              You should note that the MSR would not use sodium in any form. Liquid sodium was "tried in the 60s" as a working fluid for very high temperature plutonium breeder reactors; the stuff is so reactive (particularly with water) it's no wonder it was "a disaster." The MSR uses fluorides of actinides (uranium, thorium, plutonium) in solution with lithium & beryllium fluorides. The strong ionic bonds in these compounds make them extremely stable.

              I'm particularly fascinated by the possibilities of the liquid fluoride thorium reactor (LFTR) which would "burn" U-233 bred from thorium within the reactor itself & could be tweaked to gobble LWR waste. Here's a reasonably brief overview of the LFTR--you might find it interesting.

              *Note: the helium turbine is unproven technology, but it could be researched independent of the reactor, as could the reprocessing technologies that have been proposed. Considering the promise of the technology, I think a modest budget to investigate both would be money well spent.


              by Uncle Cosmo on Thu Apr 04, 2013 at 07:47:33 PM PDT

              [ Parent ]

              •  so say it's running at 800C (0+ / 0-)

                that's more then enough to have a steam explosion from any loose water.  Trust me, when a quake hits a MSR, it will have loose water around.

                Helium won't work, we don't have enough helium production.


                these kinds of plants are going to require us to go to Jupiter for helium :-(

                The SOlar Thermal industry is messing around with Molten salt, it's lots of flouro-silicates and flouro-chlorides,  but, it's heinous stuff.

                •  What part of "the MSR doesn't use water" (0+ / 0-)

                  are you having trouble grasping, friend? And as for water from external sources, we do know how to waterproof structures. (Heck, my basement, whose floor is about 5' underground, is so dry I need a humidifier to keep the books I store down there from dry-rotting--in Baltimore on a concrete slab with cinderblock foundations laid in 1937.)

                  Re quakes: Best solution here is not to site the reactors near active fault lines or a large body of water (which it doesn't need) & move the power via HVDC lines; but if needs must, you quake-proof the installation. Even with a reprocessing loop a MSR would be much smaller & lighter than a LWR of comparable output & amenable to the sort of quake-proofing that's been done for many years.

                  Re helium shortages: (1) "Closed cycle" = "reuse indefinitely". It's only a means of transferring heat to a turbine; it doesn't get used up. (2) A nuclear reactor generates helium as a byproduct of alpha decay (which FTR is the source of practically all terrestrial helium, which shows up in natural gas via long-lived radioactive elements like thorium & uranium). That can be recovered in the reprocessing loop. Not sure how much it is, but it's something. (3) If the Feds stopped selling off the national helium reserve at rock-bottom prices & allowed the market to dictate its cost, natural-gas producers would find it practicable to recover it from their product.

                  (Just FTR I know I'm not going to convince you--you'll ignore my arguments & throw one new objection after another at me. I'll keep replying so long as it's fun & I have the time.)


                  by Uncle Cosmo on Fri Apr 05, 2013 at 10:48:48 AM PDT

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