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Virginia US Earthquake - Nuclear Plant

  1. Aug 23, 2011 #1

    QuantumPion

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    Virginia US Earthquake -- Nuclear Plant

    The earthquake that just hit the east coast was centered on Mineral, VA, right where http://en.wikipedia.org/wiki/North_Anna_Nuclear_Generating_Station" [Broken] is. :uhh:
     
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  2. jcsd
  3. Aug 23, 2011 #2
    Re: Japan Earthquake: nuclear plants

    From reuters:
     
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  4. Aug 23, 2011 #3
    Re: Japan Earthquake: nuclear plants

    It was 5.9:

    http://earthquake.usgs.gov/earthquakes/recenteqsus/Quakes/quakes_all.php [Broken]

    Edit: I am 100 % sure it was 5.9 a while ago. Just seconds ago they have updated it:
    MAP 5.8 2011/08/23 17:51:04 37.936 -77.933 6.0 8 km ( 5 mi) SSW of Mineral, VA
    So it's now 5.8.

    Edit 2: And back to 5.9:
    MAP 5.9 2011/08/23 17:51:03 37.975 -77.969 1.0 6 km ( 4 mi) SSE of Louisa, VA

    The Operating Basis Earthquake for North Anna is 0.06 g (5.4 on
    the Richter Scale) and the Design Basis Earthquake for North Anna is 0.12 g (5.9 on the Richter Scale).
    (year 2003)

    http://pbadupws.nrc.gov/docs/ML0334/ML033440194.pdf
    http://www.expertglossary.com/definition/operating-basis-earthquake-obe
    http://www.expertglossary.com/water/definition/design-basis-earthquake-dbe

    This means there could be some damage but not for components important for safety.
    (fingers crossed) :smile:
    (If they have updated their earthquake parameters since 2003 the situation could be even better.)
     
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  5. Aug 23, 2011 #4

    QuantumPion

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    Re: Japan Earthquake: nuclear plants

    North Anna has upgraded the event from an unusual event to an alert. They are currently running on diesels.

    They upgraded to an alert due loss of offsite power and having to shut down 1 out of 4 diesels. Everything else appears to be working normally.
     
    Last edited: Aug 23, 2011
  6. Aug 23, 2011 #5
    Re: Japan Earthquake: nuclear plants

    from http://www.cnn.com/2011/US/08/23/virginia.quake.nuclear/" [Broken] about North Anna quote:
    "Amanda Reidelbach, an emergency management spokeswoman for Louisa County, said the plant vented steam, but there was no release of radioactive material."

    Why are they venting steam? WTH? I hope it's just a misreporting.
     
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  7. Aug 23, 2011 #6

    QuantumPion

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    Re: Japan Earthquake: nuclear plants

    It's secondary steam, that is a normal occurrence with trips from full power. All the steam that was going to the turbine has to go somewhere! Here's a youtube clip of what it looks like (at Surry, same design as North Anna):

     
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  8. Aug 23, 2011 #7
    Re: Virginia US Earthquake -- Nuclear Plant

    I am curious about the spent fuel pools. They are not required to have back-up power and North Anna has some 1200 tons of spent fuel.
     
  9. Aug 23, 2011 #8
    Re: Japan Earthquake: nuclear plants

    Thanks, makes sense. That video is awesome and without you explaining would have been scary as hell.
     
    Last edited by a moderator: Sep 25, 2014
  10. Aug 23, 2011 #9

    QuantumPion

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    Re: Virginia US Earthquake -- Nuclear Plant

    Don't know where you heard that but it is incorrect. The spent fuel pool coolers run off the same backup power as every other safety-related system.
     
  11. Aug 23, 2011 #10

    jim hardy

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    Re: Japan Earthquake: nuclear plants

    ""Why are they venting steam? ""

    The steam generators are vented to atmosphere through relatively small valves in order to carry away decay heat when the turbine and condenser are unavailable as when you are starting up or shutting down the plant , or when the grid goes away.
    They're called " Steam Dump to Atmosphere" valves and they're a normal means of temperature control when plant is in between cold shutdown and power operation - a state often called "hot shutdown".. it's very normal.

    Another source of steam is the exhaust pipes from the Terry Turbines that supply the makeup water to the steam generators. Ours were adjacent the Steam Dump to Atmosphere silencers.


    The water in the steam generators is ultra purified. It is separated from the reactor coolant water by the steam generator tubes.
    You could drink that condensed steam except that ultra pure demineralized water gives you a tummy-ache because it is so mineral free it depletes your electrolytes.

    Steam is normal. Do not be alarmed by that. The plant is capable of impressive displays of it, and shouild a steam generator relief valve have opened as a result of grid going down - well - that's quite noisy..
    The diesels started, they're dumping steam, sounds like they're doing fine.
    But a loss of grid doesn't happen every day - so i'm sure it's a bit hectic there just now. Pray everything goes smooth for them.

    When you lose grid the turbine piping has to cool down without help of main condensate pumps and that's sometimes a bit noisy. If you've ever heard an old steam heating radiator creak and clank - imagne one with twenty inch pipes.

    oops i see it's been handled... that youtube looks to me more like a relief valve than steam dump to atmosphere.. but i dont know that plant.

    old jim
     
  12. Aug 23, 2011 #11
  13. Aug 23, 2011 #12
    Re: Virginia US Earthquake -- Nuclear Plant

    To clarify, the link says that the spent fuel ponds are not required to have back up power, which is not the same as saying they don't have back-up power.
     
  14. Aug 23, 2011 #13

    Astronuc

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    Re: Virginia US Earthquake -- Nuclear Plant

    That's not entirely correct. That POGO article is a bit misleading.

    The pools were originally designed for less fuel, but they re-racked to increase capacity. Originally, the US government was going to take the spent fuel and reprocess. Well, that didn't happen. Then the US DOE was going to build a final repository, and that hasn't happened. Now, utilities like the one operating North Anna put spent fuel in dry storage pending some government resolution.

    The site is required to main coolability of the spent fuel pool. That pretty much guarantees that the pool cooling system has backup power. They aren't required to have an exclusive (independent) back up power system - but that doesn't mean that they don't have back up power.

    Also, the steam turbine is part of the secondary system which does not contain radioactive water, unless the steam generator tubes leak. North Anna replaced steam generators, Unit 1 in 1993 and Unit 2 in 1995, in order to remove the original SG tubing, which was prone to IGSCC.
     
    Last edited: Aug 23, 2011
  15. Aug 24, 2011 #14
  16. Aug 24, 2011 #15

    Astronuc

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    Re: Virginia US Earthquake -- Nuclear Plant

    FYI

    from - http://pbadupws.nrc.gov/docs/ML1123/ML112360103.pdf

    See also - http://www.nrc.gov/reading-rm/doc-collections/event-status/event/en.html#en47181
     
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  17. Aug 24, 2011 #16

    QuantumPion

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    Re: Japan Earthquake: nuclear plants

    For a trip where condenser vacuum is lost, full steam flow has to be vented to atmosphere. Condenser vacuum was lost because they lost offsite power.
     
  18. Sep 2, 2011 #17

    mheslep

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    Re: Japan Earthquake: nuclear plants

    Sounds like that's another possible accident problem and offsite dependency that could be avoided with a nuclear plant design based on the Brayton cycle? Yes I know the traditional PWR/BWR doesn't generate high enough temperatures, but other designs could.
     
  19. Sep 2, 2011 #18

    QuantumPion

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    Re: Japan Earthquake: nuclear plants

    It's not an accident problem, it's simply the design of the system.

    A gas cooled reactor using the Brayton cycle would still have to have a way to dump decay heat on a trip, which would involve venting gas or steam to the atmosphere.

    I don't understand your comment about LWR's not generating high enough temperatures for a Brayton cycle. You may be confusing with rankine cycle with superheated steam, which is true that most LWR's cannot produce superheated steam.
     
  20. Sep 2, 2011 #19
    Re: Japan Earthquake: nuclear plants

    The reason for having to use the atmosphere as a heat sink is the fact that the ordinary heat sink (=sea / cooling tower) is lost due to stoppage of the condenser cooling pumps. The same goes for any nuclear plant no matter what the cycle used: if you lose the power needed for utilizing the normal heat sink, you need to use an alternative one. In a PWR, the most straightforward alternative heat sink is to blow secondary steam out to the atmosphere and refill the steam generators with fresh water; in a BWR the primary steam is blown to the containment suppression pool and the primary circuit is refilled with fresh weater. An isolation condenser in a BWR makes it possible to use the same decay heat removal method as a PWR.

    Needing power for emergency feedwater pumps to replace the lost inventory is not "another" offsite dependency: that's exactly the reason power is needed after the shutdown at all.
     
  21. Sep 2, 2011 #20

    mheslep

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    Re: Japan Earthquake: nuclear plants

    The issue here, as I think I understand it, is that with the Rankine a condenser is required and that when the condenser stops the system has no way of continuing to transfer heat to the turbine and removing energy (decay heat) from the system. I don't see the need for a condensor in a Brayton. Thus such a system could could continue running turbine at lower power and bleeding off energy after a reactor trip through the normal path.

    Well IIRC 300K above ambient is typical for an LWR, where as a practical Brayton might run 700K above ambient. And I'm assuming, most likely, He as the gas. Under what trip circumstances He in a Brayton need to be vented?
     
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