[QUOTE=sweeteviljesus]
Seriously, what is so special about military nuclear power that it should be a secret? I guess that making subs run quiet probably involves classified information, but does that have anything to do with the reactor? I saw a documentary about submarines once and they noted that cameras were not allowed in the reactor room which I assume is not for safety reasons.
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In general, Navy-used reactor designs are very compact (obviously, in order to fit within the hull of a ship or a submarine) and require active control to maintain stability. One of the largest sources of noise on a submarine is the pump(s) on the coolant loop of a submarine. In power-generating nuclear fission reactors a coolant–some kind of fluid like high pressure steam or liquid sodium–is run through the core, extracting the heat (and keeping the temperature of the core low enough that the elements don’t “meltdown”). The coolant then runs through a heat exchanger–basically, a big, double-ended radiator–where it transfers its energy to the outer loop. This loop runs through a cycle that drives the generator which in turn serves to make power that drives the powershaft, provides HVAC and systems power, et cetera.
For most US submarines, the reactor system is designed such that under most regimes the coolant moves through the loops under “natural convection”, i.e. it keeps moving without having to actively pump it, and thus eliminates the pump vibration; this translates into a very silent boat, to the point that some US submarines actually radiate less noise than the ambient environment. Soviet subs, on the other hand, were noted for the amount of noise their reactors make; the deep diving, high speed Alfa class “interceptor” boats, for instance, used a high pressure steam loop that was phenomonally noisy at max cruising speed. The later subs like the Akula and the Delta-IIIs were much quieter because of better pump isolation, anechoic hull tiles, and noncavitating screw designs, but AFAIK they never developed effective natural convection reactor systems.
Reprocessing nuclear waste is expensive, somewhat hazardous, and adds more links in the security chain. On the other hand, stuffing high grade radioactive material in a crack in the ground isn’t necessarily the brightest idea, either. At the time that Carter approved a ban on breeder reactors the designs ran on unstable or marginally stable modes which were strongly opposed by the anti-nuke environmentalists as well as sensible, caution-minded experts. There are modern designs that are passively stable (that is, they can’t go critical by failure of some subsystem–overheading results in boiling off the moderator or somesuch which then slows the reaction) but the US hasn’t approved new nuclear powerplant construction since the mid-Seventies and as others have already noted, until the fossil fuel supplies are sufficiently depleted to warrant the expense and bureaucracy of building nuclear plants that probably won’t change.
The production of potential weapon products is more or less a nonissue; one can readily produce a fuel that is appropriate for power generation but nonweaponizable (i.e. won’t sustain the kind of supercritical reactor that results in an explosion). One could produce a dirty bomb from radioactive products, of course, but you hardly need highly enriched plutonium to do so; see The Nuclear Boy Scout for the story of how a teenage boy built a nuclear hazard in his backyard shed.
Controlled energy-generating fusion has been perpetually “20 to 30 years away” since the Fifties, and despite advances in computer elecromagnetic fluid dynamics simulation and superconductor materials is likely to remain out of reach in the foreseeable future. We can create fusion reactions easily enough (as the residents of Nevada are well aware) but making a controlled, sustainable reaction is tough. Also, as Spacekat notes, the reaction is extremely hot (and for the D-T cycle, produces a lot of neutrons which results in material degredation and neutron activation of radioactive isotopes of otherwise inert materials). It is, in fact, far too hot to run a coolant loop through as detailed above, so you have to extract the energy via some other process where you either stage down the temperature of the products to a level that is managable by normal materials, or you extract energy inductively from the charged plasma via a magnetoelectrodynamic generator. Both of those will require advances in the state of the art of technology, so even if you could control nuclear fusion today you’d still have years of effort into making a safe, reliable system for turning raw energy (in the form of an energetic plasma) into electricity. So, don’t be buying up shares in General Atomics in hopes of paying next year’s Christmas bill with them.
Stranger
