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Nuclear energy at sea

  1. May 5, 2009 #1
    On nuclear powered aircraft carriers/submarines/icebreakers, do the crew have to follow similar precautions as people who work in nuclear power plants such as clothing, film badges etc? Also, how much more protection does the reactor core have compared to a civilian power plant?
     
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  3. May 5, 2009 #2

    mgb_phys

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    You think the Navy wants to cut corners on safety on a $Bn sub? If there is an alarm you can hardly run away!
    Generally more - people tend not to fire 18" shells at civilian reactors.

    Do searches on 'Admiral Rickover' the man behind the US's nuclear navy
     
    Last edited: May 5, 2009
  4. May 5, 2009 #3
    What I meant was is it nessecary go through the 'everyday' precautions for radioactivity for the whole crew, as I imagined (as you pointed out), that the reactor would be well protected, and also that the majority of the crew do not go in that area. I also can't imagine that there would be as stringent precautions on a 100000 tonne aircraft carrier or an icebreaker which can (in some cases) carry passengers.
     
  5. May 5, 2009 #4

    mgb_phys

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    I would expect everybody on a sub to wear film badges (or TLDs nowadays) since a leak of any radioactive gas might go everywhere.
    Possibly only engineering wear them on a ship. Generally you keep crew compartmentalized so non-engineering staff don't get near the reactor - you don't want idiots playing with knobs!
    Even on land you wouldn't normally wear bunny suits for anything other than waste handling / isotope reprocessing where everyone also wears TLDs. People are a good way of finding spills.
     
  6. May 6, 2009 #5

    Morbius

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    James,

    On US Navy ships, most of the crew never goes anywhere near the reactor. Only the members of the
    engineering department are in the engineering spaces containing the reactor. Additionally the crew is
    not anywhere where they would need special clothing when the reactor is operating.

    As far as protection of the reactor core - a commercial nuclear power plant has MUCH, MUCH more
    protection for the reactor than would a US Navy ship. Take a look at the following graphic courtesy
    of the Nuclear Regulatory Commission that shows what the interior of a nuclear power plant looks like:

    http://www.nrc.gov/reactors/new-reactors/design-cert/apwr.html

    The reactor is the red object in the middle. the containment building is the domed tan colored building,
    the walls of which are several feet thick. However, in the interior of the containment building surrounding
    the reactor is the reactor shielding colored green in the graphic.

    That shielding is made of high density concrete. A nuclear power plant doesn't have to float - so it can
    have LOTS and LOTS of concrete around the reactor. A US Navy ship can't have that much concrete.

    There are lots of constraints on the design of a Navy ship - it has to float; space on a ship is expensive,
    while land is cheap; the Navy ship's main purpose is not to generate energy - but to be a warship - so
    most of the ship is going to "airport" / hanger for a carrier, for example. So a civilian power plant can be
    designed with MUCH BETTER safety systems than a ship - and they are.

    A commercial power plant has MUCH better protected for the reactor than does a US Navy ship.

    Dr. Gregory Greenman
    Physicist
     
    Last edited by a moderator: Apr 24, 2017
  7. May 6, 2009 #6

    mgb_phys

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    On the other hand a submarine reactor is inside a steel or titanium tube designed to withstand 200-1500m of water pressure.
    Naval reactors are smaller and simpler than civilian models and are generally sealed units that aren't refueled during their life. They also need to be tougher to take the mechanical beating of a ship moving at sea.
    Reactors on naval surface ships are similarly well protected by lots of armor plate, rather like the ship's magazine, a direct hit on the reactor would really spoil your day
     
  8. May 6, 2009 #7

    Morbius

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    mgb_phys,

    By FAR - a civilian power plant has MUCH BETTER protection than a US Navy ship.

    US Navy ships are not designed to withstand 18" shells anyway. For example, a carrier
    just flat out will not let an enemy warship come within range so that it could use 18" shells.

    A carrier has a lot of jet fuel aboard - and it would be problematic attempting to protect that.
    So the philosophy is not to make a carrier that can take hits from the enemy. The philosophy
    is to NEVER let the enemy get into a position where they can put that type of armament into
    the carrier.

    It's like in the movie "Top Gun" - "Air Boss" Johnson gets upset when the enemy planes are
    200 miles away. That's the type of "buffer" the US Navy keeps around its carriers.

    Dr. Gregory Greenman
    Physicist
     
  9. May 6, 2009 #8
    When the nuclear submarine 'Kursk' sank in 2000, there was a large explosion onboard due to a very large torpedo stored onboard. When the ship was discovered, the nuclear reactor was still intact. I was aware that civilian power stations have a lot greater quantity of protection around them in the form of concrete, but I thought that as a naval power plant would inevitably be much smaller, It would be able to have protection around it sufficient to withstand a greater impact.
     
  10. May 6, 2009 #9

    mgb_phys

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    Subs tend to be pretty strong, the Russians lost one of their nuclear powered titanium hulled subs boats in the 80s in water >1mile deep and the reactor didn't leak (so far).
    As morbius said no ship is going to survive a missile carrying a 1000kg warhead at mach 2 but the reactors are deep inside the hull and you would expect them to go to the bottom in one piece.

    Most (all?) naval reactors are also PWRs which have a bunch of inherent safety features and are relatively small. The US has had no naval reactor accidents in 50 odd years , the Russians haven't been quite so lucky (or careful) but none of the reactors in sunk submarines have exploded - or even significantly leaked.
     
    Last edited: May 6, 2009
  11. May 6, 2009 #10

    mheslep

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  12. May 6, 2009 #11

    mgb_phys

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    "They point to a history of naval and nuclear accidents in Russia and the former Soviet Union, including the Chernobyl disaster of 1986."

    This is a PWR not an RBMK - it's hardly a comparison.
    Why does nobody object to gas powered generating stations? Bhopal was a gas leak and it killed 25,000 people.
     
  13. May 6, 2009 #12

    mheslep

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    Agreed, the accident comments in the news links are a distraction. I'd like to concentrate on the exposure of HEU that these floating reactors present. There is some US or international official body (IAEA ?) that has a near term goal the elimination of all commercial use of HEU - completely zero it out - and this move by the Russians would seem to fly in the face of that goal.
     
  14. May 6, 2009 #13

    mgb_phys

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    I suppose they have to balance the safety of an existing proven sub reactor design with developing a new LEU model and they must have a bunch of HEU around from weapons disarmaments.
    I can't see the Iranians capturing a Russian power station and sailing it to Iran without the Russian navy noticing - as an alternative to enriching their own fuel.
     
  15. May 6, 2009 #14

    mheslep

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    I doubt they're reusing weapons HEU. Probably making more.
    Not the Iranians, they would then be subject to retaliation. More likely some non-state actors - something like the Taliban-Pakistani gang that hit Mumbai - direct attack or infiltration. Appears this would be manned by a commercial oil/gas drilling rig crew - ie anyone - and not Russian military.
     
  16. May 6, 2009 #15

    mheslep

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    Chinese are also using commerical / civilian HEU.
    http://www.nti.org/db/heu/china.html [Broken]
    Cochran from NRDC has an HEU ban brief here. Caveat: Cochran has a reputation as a an anti-nuclear advocate.
    http://www.nti.org/db/heu/china.html" [Broken]
     
    Last edited by a moderator: May 4, 2017
  17. May 6, 2009 #16

    Morbius

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    mgb_phys,

    ALL naval reactors in current use are PWRs. One certainly would NOT send a BWR to sea -
    because a BWR has a "free surface" - the water / steam interface. You don't want to have a free
    surface moving around in a naval reactor. One would like the power distribution to be static.

    The US Navy did send one liquid sodium cooled reactor to sea in the original Seawolf (SSN 575):

    http://navysite.de/ssn/ssn575.htm

    USS SEAWOLF was the Navy's second nuclear-powered attack submarine and the first submarine to be
    equipped with a S2G sodium-cooled nuclear reactor. But due to the difficulties of running a sodium-cooled
    reactor, the Navy decided to replace SEAWOLF's sodium-cooled reactor with a water-cooled one and use
    only water-cooled designs in the future.

    Dr. Gregory Greenman
    Physicist
     
  18. May 6, 2009 #17

    Morbius

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    James,

    NOPE - space is at a premium on a ship. A US Navy nuclear-powered ship doesn't have the big
    containment building that a commercial power reactor has - you couldn't get even a carrier to float
    with THAT much concrete / steel.

    Again - the reactor compartments are NOT designed to withstand attack. The philosophy is to keep
    the battle far away from the carrier. As for a sub - if something breaches the hull - the ship and its
    contents are lost. No armor plating is going to withstand the shock - the air in the sub essentially
    turns to a multi-thousand degree plasma.

    Dr. Gregory Greenman
    Physicist
     
  19. May 6, 2009 #18

    mgb_phys

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    I didn't know if there had been some other possibly secret designs.
    I thought somebody might have tried AGRs, to get higher power and perhaps the gas coolant could be made quieter (for subs) than the cooling pumps on a PWR.
    I don't know if you could make a gas cooled where the gas was hot enough to efficiently run a turbine without a steam pant?


    I had heard of Rickover doing a Feynman type demonstration with sodium in a water glass at a meeting to explain why he didn't want any more sodium cooled reactors on a boat!
     
    Last edited: May 6, 2009
  20. May 6, 2009 #19

    Morbius

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    mheslep,

    The only proliferation risk would be once every 3 years when the reactor is refueled with fresh fuel.
    I would hope that the Russians would guard that fresh fuel until it is safely installed in the reactor.
    Once HEU starts to be used as reactor fuel - then it becomes UNUSABLE as a bomb fuel.

    There are two university research reactors in the USA that still use HEU. The concern is not about
    the HEU that is actually in the reactor - but fresh fuel. Neither university keeps a supply of fresh
    fuel in reserve. Fresh fuel is delivered "just in time" to be loaded in the reactors.

    Dr. Gregory Greenman
    Physicist
     
    Last edited: May 6, 2009
  21. May 6, 2009 #20

    Morbius

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    mgb_phys,

    I would think that the gas coolant would be noisier. The gas has a lower density, hence lower heat
    capacity per volume. That means the flow rate for the gas is going to be higher than the water -
    hence noisier. In fact, that's the reason they tried sodium. For quiet operation, you don't go to a
    gas - you go the OTHER way - you want as DENSE a coolant as possible. Something with a high
    density and high heat capacity like sodium - doesn't have to be pumped as fast as water and most
    certainly a LOT slower than a gas.

    Dr. Gregory Greenman
    Physicist
     
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