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Originally Posted by filthyvermin
thanks!
how about nuclear subs? seems like those wouldn't be so great to leave unattended. i think aircraft carriers have nuclear power plants on them too
i've just been listening to this stupid zombie apocalypse book, and wondering about that
wildfires would probably be really bad too
nuclear material inside a reactor only becomes an issue if it somehow beaches containment (ie it gets into the ground or atmosphere or whatever)
when it’s inside the designed containment it is totally safe
the reason it can be dangerous is that while you can just stop burning coal or oil to stop the heat being produced if you want to shut down one of those plants, nuclear reactors are not that simple. the nuclear material inside of a nuclear power plant will continue to produce what is called “decay heat” for days/weeks even after it is shut down. this is going to be energy generated at like 7% (and slowly decaying down to 0% over the course of days/weeks) of normal operating energy
obviously this is easy to deal with as long as everything is working. just keep pumping cool water over it until it fully cools down. the issue becomes when you can’t or aren’t doing this. even at 7% energy, without a constant supply of cool water the reactor will heat up VERY quickly. when it gets hot enough there could be small steam explosions that breach containment (not nuclear explosions) and/or the nuclear material and get so hot it starts to melt (aka a metldown) and then it melts through containment. That is when you have an issue because radioactive material is now in the environment.
where it gets tricky is that usually the electricity used to power the pumps that deliver cold water to the nuclear reactor and keep this from happening is powered by the reactor itself. so if that goes down (due to natural disaster or what have you) there is no electricity to power the pumps to keep the reactor cool.
of course nuclear engineers aren't morons. they put in all kinds of back up systems for when this happens. diesel powered generators. redundant back up pumps. passive cooling (cooling that requires no electricity to work). but the extent a reliability of these systems is not necessarily consistent from plant to plant. the newer the plant is the better the safety systems.
however, due to weird political fear mongering, the US has not built a commercial nuclear power plant since I think 1979. The designs for plant has gotten SOOOOOO much better since 1979 but that doesn't do you any good if you don't build any. so people are too scared to replace old nuclear power plants with new ones so the solution has been to just keep limping along with the much less safe, clean, efficient ones we built 50+ years ago. doesn't make much sense but there you go. most of them do not have passive safety systems and the fail safe situation is not nearly as good as it could be. my guess is you would have at least a few if not many melt downs from commercial plants (if they were all current generation plants I would guess you would have close to zero melt downs, but obviously that is not the case). its like we are driving cars with no seat belts, air bags, anti-lock breaks, crumple points, etc. even though we have all the technology and designs to have cars like that, we are sticking with the ones we designed and built in the 70s.
the US Navy is a different story. they aren't really hampered by politicians or the whims of the public. they kind of just do whatever they want. as such their reactors have always been far more safe and advanced. any subs out at sea would eventually just sink to the bottom of the ocean I would guess and even if the melted down it probably wouldn't be a HUGE deal (in the context of a zombie apocalypse or whatever) several thousand feet underwater. I think most of the ones in port are running on shore power and the reactors are in hot standby and already just on decay heat so probably wouldn't be a huge issue. ditto for carriers that are at shore. carriers out at sea could be dicey. if they did meltdown i think they would also just sink too and thus probably wouldn't have a huge effect.
However my guess is the likelihood of a navy reactor melting down unsupervised would be pretty low given their current level of design. but I am not as familiar with them. and if they did I don't think they would pose anywhere near the threat of a commercial power plant on land near a populated area.
anyways that was kind of long winded. sorry. hopefully it answered your question.