1. T.Trian
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    T.Trian Overly Pompous Bastard Staff Supporter Contributor

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    Nuclear Reactors and Firearms

    Discussion in 'Research' started by T.Trian, May 25, 2014.

    So, @KaTrian and I are writing a scene in our sci-fi WIP where a character is chased into the reactor room of a nuclear-powered space ship. We have a few questions regarding the practicalities of that scene.

    First, what kind of a reactor would a space ship have if it's roughly twice the size of the larger nuclear-powered aircraft carriers like the USS Enterprise? Would it be a pressurized or boiling water reactor, radioisotope thermoelectric generator, graphite-moderated reactor, or something else? How many reactors would it have? Bear in mind that the ship is space-to-space only, so it does not need the power of planet-to-space rockets and shuttles if that matters at all.

    Second, what possible consequences could there be if you fired a rifle near or at a nuclear reactor (the kind depending on what would be most likely on such a vessel)? Or threw a concussion grenade close to one?

    The lone character chased by the others essentially plans to hide close to one of the reactors, hoping that that way she could fire at her pursuers at will while they would have to pick their shots very carefully or risk causing a nuclear disaster that would kill them all.

    Now, for that to be even borderline plausible, we need to know a bit more about the design of such reactors and so far Google hasn't provided us with definite answers.
    In order to make small arms fire dangerous, should the chased character go directly to the nuclear core? Or is that too shielded well enough that no rifle could penetrate it, i.e. shooting at it would be perfectly safe? Should she head into the containment building?

    Which parts in a nuclear power system could cause a nuclear explosion (or some other such immediate disaster) if fired at/subjected to the blast of a concussion grenade?

    Thanks in advance! :cool:
     
  2. Robert_S
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    Robert_S Contributing Member

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    I'm thinking (not an expert here, just did some quick research into the nuclear reactors you listed) that a radioisotope thermoelectric would have greater appeal since there is fewer steps in the process to turn it into electricity. Storage and utilization of water introduces another point of failure. Thermoelectric is more direct.

    Are graphite reactors used much? Chernobyl was a graphite-moderated reactor, so I'm thinking they may be less desirable because of the number of accidents.

    I don't think there would be much effect firing normal gas charged projectile or concussive weapons because reactor walls are pretty thick as are the walls of any cooling system for them. The most serious consequence would be damage to computer systems that control and monitor or electrical systems that feed the controls.

    However, when you say concussion grenades, are you referring to flash-bangs? The stun grenades law enforcement use?
     
  3. T.Trian
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    T.Trian Overly Pompous Bastard Staff Supporter Contributor

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    I'm also under the impression that graphite reactors are starting to be obsolete. The thing about radioisotope thermoelectric is that what I've read about them, they don't produce nearly as much energy as, say, pressurized or boiling water reactors.

    I know they use those radioisotope-thingies in Cassini-Huygens and the Voyager space probes, so they seem fairly low-maintenance, but would they be enough to power such a large ship? Of course there would probably be more than one reactor anyway, no matter what kind we go with, but do the radioisotope generators have good enough of an energy output/size ratio since size/room is always an issue aboard space ships?


    That's kinda what I was afraid of. If small arms fire can't damage a nuclear reactor/nuclear core, we have to figure out another plan for the character or then she thinks her plan is a good one and ends up in even bigger trouble when the bad guys fire at will even though she's next to the nuclear core. Or the bad guys don't know much about nuclear reactors either and are afraid to hit the core. :D

    I was just wondering, if you enter the containment building and go directly to the nuclear core, would the core shroud be enough to stop rifle bullets? We're talking about rounds equal to 7.62x51mm NATO and .460 Weatherby Magnum, so they're pretty powerful, but enough to damage the core...?


    Nope, not the same kind: flashbangs are pretty much non-lethal whereas concussion grenades are basically lethal, causing damage via shockwave/overpressure, kinda like the MK3 concussion grenade the US Army uses. They contain around 8 oz. of TNT and are generally more effective in enclosed spaces like bunkers (and narrow space ship corridors) than fragmentation grenades that rely more on shrapnel dispersal for damage.
     
  4. Robert_S
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    Robert_S Contributing Member

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    Well, there's a lot of ways to cause a nuclear accident. I'll post a synopsis from some of the major accidents in our history:

    Chernobyl:

    The disaster began during a systems test on Saturday, 26 April 1986 at reactor number four of the Chernobyl plant, which is near the city of Pripyat and in proximity to the administrative border with Belarus and the Dnieper river. There was a sudden and unexpected power surge, and when an emergency shutdown was attempted, an exponentially larger spike in power output occurred, which led to a reactor vessel rupture and a series of steam explosions. These events exposed the graphitemoderator of the reactor to air, causing it to ignite.[4] The resulting fire sent a plume of highly radioactive fallout into the atmosphere and over an extensive geographical area, including Pripyat. The plume drifted over large parts of the western Soviet Union and Europe. From 1986 to 2000, 350,400 people were evacuated and resettled from the most severely contaminated areas of Belarus, Russia, and Ukraine.[5][6]According to official post-Soviet data,[7][8] about 60% of the fallout landed in Belarus.

    Fukushima:

    Immediately after the earthquake, following government regulations, the remaining reactors, 1–3, automatically SCRAMmed; control rods shut down sustained fission reactions. Although fission stops almost immediately with a SCRAM, fission products in the fuel continue to release decay heat, initially about 6.5% of full reactor power. This is still enough to require active reactor cooling for several days to keep the fuel rods below their melting points. InGeneration II reactors like the GE Mark I, cooling system failure may lead to a meltdown even in a SCRAMmed reactor.[26]

    Coincident with the SCRAM emergency generators were automatically activated to power electronics and cooling systems. The tsunami arrived some 50 minutes after the initial earthquake. The 14 meter high tsunami overwhelmed the plant's seawall, which was only 10 m high,[7] with the moment of the tsunami striking being caught on camera.[27] The tsunami water quickly flooded the low-lying rooms in which the emergency generators were housed.[28] The diesel generators were flooded and began to fail soon after, their job being taken over by emergency battery-powered systems. When the batteries ran out the next day on 12 March, active cooling systems stopped, and the reactors began to heat up. The power failure also meant that many of the reactor control instruments also failed.[26]


    Three-Mile Island:


    The initial cause of the accident happened eleven hours earlier, during an attempt by operators to fix a blockage in one of the eight condensate polishers, the sophisticated filters cleaning the secondary loop water. These filters are designed to stop minerals and impurities in the water from accumulating in the steam generators and increasing corrosion rates in the secondary side.

    Blockages are common with these resin filters and are usually fixed easily, but in this case the usual method of forcing the stuck resin out with compressed air did not succeed. The operators decided to blow the compressed air into the water and let the force of the water clear the resin. When they forced the resin out, a small amount of water forced its way past a stuck-open check valve and found its way into an instrument air line. This would eventually cause the feedwater pumps, condensate booster pumps, and condensate pumps to trip at around 4:00 a.m., which would in turn cause a turbine trip.[14]

    With the steam generators no longer receiving feedwater, heat and pressure increased in the reactor coolant system, causing the reactor to perform an emergency shutdown (SCRAM). Within eight seconds, control rods were inserted into the core to halt the nuclear chain reaction. The reactor continued to generate decay heat and, because steam was no longer being used by the turbine, heat was no longer being removed from the reactor's primary water loop.[15]


    Back to discussion:
    It appears that even a SCRAMmed reactor will generate enough heat to cause a meltdown if it's not continually cooled. The cooling system of your reactor should probably be the focus, not the core itself. This knowledge makes the events in "Aliens" more reasonable, since any minor damage to a reactor can be countered by a SCRAM and cooling, unless the cooling system failed.
     
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  5. Robert_S
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    Robert_S Contributing Member

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    To add, anything that pumps liquids will have, well, a pump and valves, sometime check valves to prevent backflow.
     
  6. T.Trian
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    T.Trian Overly Pompous Bastard Staff Supporter Contributor

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    So it would actually work better if she headed to the cooling systems? Any idea which parts of the cooling system are the most vulnerable? The computers? The coolant pump? Some of the pipes/tubes (if there are any out in the open)?

    Is there anything that could cause instantaneous or almost instantaneous danger? Or at the very least some irreversible process that will result in their deaths?
     
  7. Robert_S
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    Robert_S Contributing Member

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    Perhaps an electrical system, something that is the single feed to the reactor from both main power source and any backup system. It could cause a surge due to shorting, that would cause another Chernobyl.
    Otherwise, you'd need a full cooling system breach, where the core is not getting any cooling.

    If as a result of the electrical system being damaged, a check valve got stuck open, it could cause already hot coolant to flow back to the core or drop in level to expose the core. that would cause a fairly immediate problem.
     
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  8. T.Trian
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    T.Trian Overly Pompous Bastard Staff Supporter Contributor

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    Thanks a lot! I think we can work something out with what we got now. :cool:
     
  9. Morristreet
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    Just to add a concept here...

    If you are detailing a spacecraft, then solid reactor systems like Graphite are out, as they require air cooling, or massive radiator fins to deal with the waste heat. For a dramatic effect, why not a Sodium cooled reactor? That allows for a very high temperature coolant, that if exposed to the atmosphere, would immediately ignite and generate not only radiation, but also poisonous gas as it burned? A number of nuclear reactors on soviet submarines are sodium or liquid metal cooled, as such, a leak can be disastrous. They tend to have to flood them with sea water to fix a SCRAM which also kills the reactor core.

    High temperature coolant would also possibly mean non-metallic piping, to reduce weight, but that would also be sensitive to impact, such as gunshots. Glass piping, and a lead bullet??

    For my money, go with a high temperature sodium cooled reactor. You truly could get a lot of bang for your buck with hthat one.
     
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  10. Robert_S
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    Robert_S Contributing Member

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    You obviously have more knowledge about nuclear reactors than I. I did some preliminary research because the knowledge may come in handy for me in the future.

    I had to look up bullets because I thought they were no longer made of lead, but it appears they still have lead at the core and only jacketed in copper. Research and reasoning tells me the lead is for mass, to impart more energy, and the copper is so they can use a heavier charge for greater muzzle velocity.
     
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  11. T.Trian
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    T.Trian Overly Pompous Bastard Staff Supporter Contributor

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    Thanks a bunch, that sounds perfect. I'll have to read about those a bit 'cause as the story stands now, the reactor is also malfunctioning; in the current version there's a problem with the cooling system, but since the characters stranded aboard the derelict ship (the good guys) aren't scientists, they have no idea how to fix it, so there's also the danger that the reactor will overheat anyway.

    Any ideas what kind of a malfunction could be in a sodium cooled reactor that would essentially give the ship anything from a day to a few months before things get critical unless someone does something about it? As it stands now, the problem has essentially resulted from neglect since the ship has been adrift in space without any maintenance for a long time.


    @Robert_S, that's what I've also understood about bullets although I don't know much about them (never reloaded, so haven't even put together a cartridge much less cast bullets).

    The bad guys are firing the 7.62x51 round with a 175gr/11g FMJ bullet which travels roughly 2,580 ft/s (790 m/s) and imparts 2,586 ft·lbf of energy, so I'd imagine even thinner metal pipes wouldn't stand a change.
     
  12. Morristreet
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    Morristreet Member

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    Nuclear Reactors in all of their aspects fascinate me, they always have.

    If you can get your hands on it, the book Saturn Rukh, by Robert Forward has a team of explorers using a sodium cooled reactor as their power source to explore the upper atmosphere of Saturn, and at one point, the reactor fails. Sodium reactors are good for general failsafe, because the system is designed to be a fail and walk away technology. If the system begins to fail, best thing to do is leave it. The metal keeps circulating, as long as the piping is intact, and will keep cooling until it solidifies, while the core remains immersed in a solid metal casing that also acts as a hard radiation shield.

    That does not mean that there aren't many possible points of failure. The most obvious being, the control rods, if they do not drop, or get stuck, then the system cannot shut down, and will continue to generate heat in a possible runaway that can cause the Sodium to begin to boil. That could also be why the ship was abandoned. The reactor began to fail, so it was abandoned. But, it did not detonate, and eventually cools off enough for the ship to be boarded again.

    http://en.wikipedia.org/wiki/NaK is the alloy of Sodium and Potassium that was used by the Soviets in their nuclear powered satellites. It remains liquid at room temperature, so it allows for easy maintenance of the reactor, unlike pure sodium. Unfortunately for your heroes, it likes to burn in the presence of oxygen...

    http://en.wikipedia.org/wiki/Liquid_metal_cooled_reactor gives a good rundown of what has been done with liquid metal cooled reactors, and their turbulent history so far.

    In my view, if the ship is still in poor shape, then treat it like they treated the Galactica in the BSG series, cost cutting measures meant the piping may not be all properly done, so it either leaks, or is corroding. So if the reactor gets too hot, you may get a pipe burst. Which would be as lethal as anything else in the close environment of a spacecraft where you cannot vent to the outside air or water ... there is none.
     

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