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The EM2 Reactor Design

  1. May 10, 2015 #1
    I read a little bit about General Atomics EM2 reactor in the December issue of Nuclear News that someone had brought to work recently. I haven't had a chance to read all of the article and I am curious about this reactor design. Are any of you involved in it?

    It claims to be able to run for 30 years without re-fueling on even DU as an initial fuel. Then it goes on to claim that it has a low weapon proliferation, even though the thing is obviously a breeder reactor that runs most of its lifetime on plutonium (from U238 neutron capture/-beta decay to PU-239).

    It seems to present a reactor design that would put uranium enrichment out of business, at least for a long time. Even though I work in the nuclear fuel cycle side of things, I still find this design exciting if it is true. But it seems too good to be true.

    What are the cons to this? Is it even a proven design? There is actually so much nuclear waste available, if even half the claims by General Atomics are accurate, this could provide power for a long long time if this thing works.
     
  2. jcsd
  3. May 10, 2015 #2

    etudiant

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    The concept is surely attractive, as always, the devil is in the details.
    This is a high temperature gas cooled reactor, using helium as the coolant and as the working fluid for the associated turbines.
    Making that work in real life is a bear. Google Fort St Vrain reactors, an earlier GA design.
    The system worked, but had enough troubles that eventually the utility shut the reactors and switched to natural gas.
     
  4. May 12, 2015 #3

    jim hardy

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    I talked with some engineers at that plant. They were enthusiastic about the equipment.
    According to them, management was a bit of a mess. Corporate headquarters in Holland and engineering in California, so getting a decision was quite a gauntlet.
    The project was behind schedule and over cost. The utility had contracted for kilowatts so there were gas turbines burning expensive jet fuel to provide it... imagine the money pit for GA.

    I think the failure was more one of management science than of nuclear science.
     
  5. May 12, 2015 #4

    etudiant

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    Management is always the biggest risk in any complex endeavor, as there are many more ways to screw up than to succeed.
    That said, behind schedule and over cost does suggest engineering issues of some size, even if the engineers involved were completely on board.
     
  6. May 12, 2015 #5

    jim hardy

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    yes there was significant trouble with "Pelton Wheel" coolant pumps.
    It was 1973 i think... i just don't remember details...
     
  7. May 12, 2015 #6

    jim hardy

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    probably this:

    from
    https://inlportal.inl.gov/portal/server.pt/directory/nrc_published_material/2656?DirMode=1# [Broken]https://inlimages.inl.gov/imageserver/plumtree/portal/public/img/sp.gif
    at

    https://inlportal.inl.gov/portal/server.pt/directory/nrc_published_material/2656?DirMode=1# [Broken]


    they had water ingress from coolant pump bearings .
     
    Last edited by a moderator: May 7, 2017
  8. May 13, 2015 #7

    etudiant

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    Thanks for the extra clarification.
    The failure of the FSV installation was a tragedy, imho. Success might have shifted the US towards a much more attractive nuclear reactor design and clearly the people who worked there understood that they were pioneering a potential game changer.
     
  9. Jun 3, 2015 #8

    mheslep

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    I've found that the two, management and design, are typically tightly coupled. A robust, well understood, hopefully elegant design tends to be tolerant of minimally competent management. But take a fragile design which forces compounding complexity, in this case very high temperature gas against an incomplete understanding of the required metallurgy, and the most competent management is apt to fumble.
     
  10. Jun 3, 2015 #9

    Astronuc

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    I still see a lot of that even today.

    There was an effective solution to this based on gas cooled bearings and magnetically supported bearings. Interesting comment about Incoloy 800H, since Incoloy 800 has been successfully used in steam generator tubing in Siemens PWRs. However, the industry was young in the 1960s, and there were assumption made about steels and nickel-bearing alloys that proved incorrect. Inconel 600 was used in most of the initial steam generators (even thought it was supposed to last 40 years), and most of that has been replaced at great expense to utilities. Had utilities realized that they would have to replace the steam generator tubing after 15 to 20 years, most might not have ordered nuclear plants, or rather they would have pushed for a better material.
     
  11. Jun 3, 2015 #10

    jim hardy

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    Indeed early stainless tubed boilers were disappointments. We had to replace ours, also get all copper(brass) out of the feedwater system and change water chemistry. Condensers we retubed with titanium and feedwater heaters with suitable stainless.

    I believe FSV's superheater could have been replaced.
    Perhaps because it was only one plant there was not much of a perceived return on investment for developing the skillset to do it... or perhaps it was an excuse to get the financial albatross off their necks...
    I'm no business guy.


    That plant made 1000 degree steam at 2400 psi, same as fossil plants of its day.

    A quick Carnot with Tcold at 75F and Thot at 1000F compared to 525F(typical PWR?).
    Absolute °F being °F + 460,
    1- 535/1460 = 63%
    1- 535/985 = 46%
    real plants approach 70% of those numbers,

    That nuclear heat is "too cheap to meter" means it's too valuable to be thrown away in low temperature cycles. It can displace those expensive BTU's from burning carbon.
    And we owe Mother Nature that consideration

    I was really disappointed to see Fort St Vrain fail.

    old jim
     
  12. Jun 3, 2015 #11

    Astronuc

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    Back in the 70s, there were plans for at least 8 gas-cooled reactors after FSV. IIRC, the thermal efficiency was expected to be about 42%, which was much better then the ~32-35% for LWRs. I'll have to dig up the information later.

    It was a host of technical problems that led to the shutdown of FSV. The Incoloy degradation and steam intrusion into the primary circuit were perhaps the two critical problems at the top of the list. At the time, I was hoping to help solve some of those problems, but the utility decided to give up.

    In my first job out of grad school, I worked at a company that consulted with PS of Colorado and FSV. In my current job/location, I just learned today that there are some folks who worked on FSV. I'll have to track them down.

    With regard to Carnot efficiency, one has to look at Thot and Tcold across the turbine, or Tin/hin to the HP turbine and Texit/hexit from the LP turbine. The work output comes from the change in enthalpy across the turbines.

    List of operated and cancelled US graphite-moderated, gas-cooled reactors.

    Code (Text):
        Unit        MWt   MWe   Dates
                         Gross
    Peach Bottom 1  115   42    January, 1967
                               November, 1974
                           
    Fort St. Vrain  842  342    January, 1974
                                August,  1989

    Planned, but cancelled ~1974-1975
    Fulton 1       3000 1200    **
    Fulton 2       3000 1200    **
    Summit 1       2000  781    Planned, 1974
    Summit 2       2000  781    Planned, 1978
    St. Rosalie 1  1300 3333    Planned, 1978
    St. Rosalie 2  1300 3333    Planned, 1978
    Vidal 1        2000  779    **
    Vidal 2        2000  779    **
     
    Last edited: Jun 5, 2015
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