Nuclear Power in movies question

CptColumbo

Just One More Question
CptColumbo
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Can someone tell me if there was no one to run a Nuclear Power plant, such as in a movie where everyone disappears (the Living Dead movie, Night of the Comet), what would happen to the plant? Would it meltdown, or just run down? I've always been curious about that, and just read the new Stephen King book and it reminded me of the problem I had with these stories.
 
My understanding is that most if not all critical controls operate in "fail safe" mode. That is, if something fails, annunciators will wail and lights will flash and shutdown will occur IF there is no human intervention. Indeed, the partial meltdown at Three Mile Island and the steam explosion at Chernobyl occurred because control room operators DID intervene. Unfortunately, they intervened in the wrong way. At TMI a gauge showing coolent level was obscured by a repair tag hanging from a valve above the gauge. No one bothered to look under the tag and the operators assumed the warning signals were wrong and overrode them. At Chernobyl the operators were running a systems test that required disconnecting some automatic safety circuits and putting the reactor in an unsafe condition...with what should have been predictable results.
Bottom line- safety systems tend to work better than clueless humans.
 
It depends. Most civilian reactors will hapily shut down. Some of the old soviet I'm less certain of. Militry ones tend to be classified.

The real problem kicks in if whatever got rid of the humans damaged the reactor (say by twisting the control rods or the like).
 
geni said:
It depends. Most civilian reactors will hapily shut down. Some of the old soviet I'm less certain of. Militry ones tend to be classified.

The real problem kicks in if whatever got rid of the humans damaged the reactor (say by twisting the control rods or the like).
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As far as military reactors are concerned, they are just simple water cooled reactors. If the crew walks away from the plant while critical, it will continue to run at a steady power level for a while. Eventually, minor steam leaks will deplete the steam plant of water and the feed pumps will fail. With no steam to cool the reactor, the coolant will heat up and power will drop, but decay heat will keep coolant temperature rising. Some reactor plants will drive in rods automatically if coolant temperature gets too high, effectively shutting down the reactor. With no human intervention, and no separate automatic emergency cooling system, the fuel could overheat and release fission products to the coolant. The fission product activity will remain inside of the plant unless it overheats too much and a relief valve lifts (into the ocean).

If whatever got rid of the humans damaged the reactor power supply or control circuitry, the reactor would scram (automatic shutdown) and cool down as steam continues to be drawn from the steam generators. Power would be lost to coolant pumps soon after unless shore power was connected.

All in all, it is not something we want to see happen to a reactor plant. It takes a day to cool down a reactor, and weeks for decay heat to go away.

Ranb
 
Ranb said:
All in all, it is not something we want to see happen to a reactor plant. It takes a day to cool down a reactor, and weeks for decay heat to go away.
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Not exactly Rapture Ready, then, are they?
 
blutoski said:
Not exactly Rapture Ready, then, are they?
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well it's not like they'd explode. I'd say having it do a rather messy shutdown over a week or so would be the least of your worries, when everyone's disappeared. any civilian reactor worth it's salt wouldn't be a problem.
 
In a pressurized commercial plant: The plant would operate normal for a while. If the plant is running self-sustaining, then it is supplying electricity to itself and it would continue to run until offsite power is lost—causing the turbine—and then the reactor to trip or something else causes the reactor to trip. Emergency diesels should come online and supply power to emergency systems—usually there is about a week of fuel for the diesels.

With no accident in the plant, the core would shut down via control rods, but would still produce a fair amount of heat from decay of radioactive material. If the diesels are running, and emergency systems would be available to keep the plant cool for a period of time…it is difficult to say how long or if they would turn on properly. If cooling systems are not available, then steam and high pressure could form in the core more quickly and the fuel would start to fail. If hot enough, it might melt the bottom of the vessel, but I am not sure. If the fuel did melt through, it should fall into a pool of water that the emergency systems flooded containment with. If the emergency systems didn’t turn on, the fuel would start to melt through the concrete…there is usually at least 15 to 30 feet of steel reinforce concrete under the vessel.

There would be many different scenarios of what could happen…if a design basis accident occurs, the plants are typically designed to operate for 30 minutes without any operators taking any action and not cause any danger to the public. An accident would make everything worse because of energy release via steam etc into containment. Emergency systems would be needed to avoid the containment from failing. I don’t know how the concrete/steel containment would fair without emergency systems operating--since that is outside the design basis of the plant.

This is very brief and can really be amplified and debated.

glenn:boxedin:
 
so for a more realistic question that occurred to me the other day. Suppose bird flu does mutate to become readily transmissible from human to human. Suppose it retains roughly 60% lethality and we don't figure a cure out fast enough. Suppose further that it has a long enough incubation that pretty much everyone catches it.

So over the course of a few months to a year or so, world population drops to 40% of today. What happens to the power plants, etc? Is there a plan to safely decommission them if there's neither the trained man-power nor the need to keep them humming in a post-apocalyptic world? When would this plan need to be implemented? Or would everything go to pot and radiation kill off the lucky sobs who survived the flu? Would the radiation kill the flu off and save humanity?
 
rudar said:
so for a more realistic question that occurred to me the other day.

...

world population drops to 40% of today
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Anyone know of a flu pandemic that's killed 60% of the existing population at one blow? :eek:

At least we wouldn't run out of oil reserves as quickly... :boggled:
 
Naval reactors can be lined up for long term emergency cooling, as long as there is not excessive decay heat. The crew can even walk away for an extended period of time, and the reactor will remain safe to start again in the future. I'm sure there are similar procedures for civilian reactors.

Ranb
 
nothing much would happen to a US plant.

Soviet, and especially the plants in some of the former Soviet blocks -- ouch!

Like they should not be operating now.

And if zombies killed everyone, hey, at least the Soviet plants would kill the zombies. I should think if you have zombies, a nuke plant explosion would be a good thing.

This from someone that KNOWS.

Every week I get to see the love hogwarts fly over the house (low enough to rattle the windows), on their way to guard the local nuke plant. Oddly this question HAS come up. (about what if everyone is dead....)

I guess we will just be MORE dead.
 
kittynh said:
And if zombies killed everyone, hey, at least the Soviet plants would kill the zombies. I should think if you have zombies, a nuke plant explosion would be a good thing.

This from someone that KNOWS.
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Maybe irradiated brains taste better.
 
kittynh said:
nothing much would happen to a US plant.

...And if zombies killed everyone, hey, at least the Soviet plants would kill the zombies. I should think if you have zombies, a nuke plant explosion would be a good thing. ..
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But all the cockroaches would survive. They would be the new rulers of the earth.

glenn:boxedin:
 
kittynh said:
I should think if you have zombies, a nuke plant explosion would be a good thing.
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Years ago a co-worker was at a briefing given by the folks at the Vermont Yankee nuclear plant. He kept asking what would hapen if the plant exploded (Which is NOT the sort of question you ask people in the nuclear industry, since nukes cannot explode....at least in a nuclear way.) Well, he was told this but kept asking anyway. A plant engineer firmly told him-again- that the plant could not explode...and then added, "Well, worst case there COULD be a "high pressure steam disassembly". He told this to me and then said that a high pressure steam disassembly sure as hell sounded like an explosion to him.
 
CptColumbo said:
Can someone tell me if there was no one to run a Nuclear Power plant, such as in a movie where everyone disappears (the Living Dead movie, Night of the Comet), what would happen to the plant?
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In a movie, the plant would obviously detonate in a mushroom cloud in a matter of minutes. (Unless the intrepid heroes can intervene 1 second before the end of the countdown.)

Movie-makers never did care much for real-world accuracy.
 
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