how long till the electricity fails?

[Scott Ellison]

About 20% of United States' and 12% of Canadian electrical generation comes from nuclear power plants. Nuclear plants can operate a long time between refuelings – 500 days is a typical quoted figure, and some plants (Brunswick 1 and Pickering 7) are notable for having gone more than 700 days between refuelings.

This statement needs correcting. The above mentioned units ran for a long time between OUTAGES. The assumption that an outage equals refuelling is wrong. The Canadian nukes are called CANDU reactors. Thier big point is On-power refuelling. They can and must change out fuel bundles daily to maintain full power output. Without this operator controlled refuelling the units would poison out within in a week.

[MEBuckner]

Moderator's Notes:

Hi, Scott Ellison; welcome to the Straight Dope Message Boards.

1. We ask that threads on columns by Cecil or by the Straight Dope Science Advisory Board ("Staff Reports") include a link to the column in question, like this one: When the zombies take over, how long till the electricity fails? (http://www.straightdope.com/mailbag/mzombiepower.html)

2. "When the zombies take over, how long till the electricity fails?" was actually one of our Staff Reports, not one of Cecil's columns, written by our own Una Persson, the Goddess of Coal and Other Things Related to Power Production. I'll move this thread from the "Comments on Cecil's Columns" forum to the "Comments on Staff Reports" forum.

[MEBuckner]

By the way, good column, Una!

[Una Persson]

About 20% of United States' and 12% of Canadian electrical generation comes from nuclear power plants. Nuclear plants can operate a long time between refuelings – 500 days is a typical quoted figure, and some plants (Brunswick 1 and Pickering 7) are notable for having gone more than 700 days between refuelings.

This statement needs correcting. The above mentioned units ran for a long time between OUTAGES. The assumption that an outage equals refuelling is wrong. The Canadian nukes are called CANDU reactors. Thier big point is On-power refuelling. They can and must change out fuel bundles daily to maintain full power output. Without this operator controlled refuelling the units would poison out within in a week.

Scott

The article I referenced stated:
Long periods of operation. Nuclear power plants are designed to operate continuously for long periods of time. They can run about 540 days before they are shut down for refueling. The longest continuous run by a light water reactor is Brunswick Unit 1. which completed a 707-day run in 2002. The longest run of any type of reactor is 894 days, achieved by the Pickering 7 plant, a heavy-water reactor in Ontario, Canada (Canadian CANDU reactors can be refueled while operating).
So in this case they seem to be saying that Brunswick Unit 1 did go 707 days between refueling outages, whereas for Pickering 7 it refers to a run by "any type" of reactor. Since it was mentioned immmediately after speaking on refueling, and because I did not know that Pickering 7 was a CANDU reactor, I may have made an assumption for that which is unwarranted.

Your point on CANDU's and continuous refueling is a good one as well. I was likely being US-centric from the nuclear standpoint, but this was due to me trying to limit the article to be somewhat generally readable, not trying deliberately to ignore the variety of power plants in general.

And thanks for reading and commenting! (and you're welcome, MEBuckner!)

[RiverRunner]

By the way, good column, Una!

Yes, it was quite good. I can't believe, though, that we had an entire column referencing Night of the Living Dead-style zombies without even one mention of 1920's-style undeath rays. Unconscionable, I call it.


RR

[BrianJ2]

I think I know the guy who sent in this question. :) :D

[user_hostile]

My cousin, who is a nuclear engineer working in OK, once told me a story of a "hard" shutdown on a steam turbine in northern AZ about 25 years ago.

He was working in a power plant in the office on some power issues and remembered hearing a whining crutching sound when somebody came rushing into the office and said "we lost unit xxx." He suddenly realized that the unit which gave up the ghost was suppose to be undergoing an inspection and maintenance. When he got to the unit on the floor, everybody was trying to figure out what happened. Finally there was a quick call to the control room determined that in addition to cutting the steam (per the procedure), somebody had shut down the lubrication pump within a minute of cutting power to the turbine (not to procedure). It turned out a new guy (in training; I’m not aware that he was a zombie at the time) had seen that the juice to the turbine had been turned off and the lube pumps were still running. Being decisive, the non-zombie guy shut down the lube pumps too. My cousin was stunned, especially since the indicators showed that the turbine was still spinning and asked him why he did that. The non-zombie guy was offended by the question and argued he was "showing initiative". "Well" my cousin said, "your initiative will be rewarded." Being a coal fired plant, he told the non-zombie guy his new job would be to turn out a dozen ash, sulpher, and mineral content reports a day (typed—remember no desktop pc’s then) involving samples of coal for the boilers for the next 12 months. (Question: did non-zombie guy become a zombie at that point?)

The non-zombie guy had powerful connections [of a sectarian nature unfortunately] within the organization, which my cousin acknowledged could be a career breaker for him, but calculated that even they couldn't rationalize away a boner like this. As far as he could tell nobody ever question his decision front of him or via the rumor mill.

From whatever else I can remember, my cousin said it took normally about 30 minutes for the turbine to coast to a stop (is it really that long?). When the lubrication was cut however it stopped in less than three minutes and melted partially through the support mounts and destroyed most of the turbine blades and stators.

[Stephi]

So there you have it. As to your final question, I can suggest a better tactic than relying on solar. Go to the abandoned hardware stores, load up a flatbed trailer with gasoline generators, and take them and a few dozen tanker trucks of gasoline to your house. You could have power for a long time, possibly years or more, until the zombies finally come for you.

Erm, would that work? I thought gasoline goes "stale" after a couple months or so?

[Chronos]

And what about decreased demand? At the very least, sudden zombification seems to predominantly occur at night, so one would expect demand to be frozen at nighttime levels. Add in power draws which require continuous human attention, zombie-induced damage tosome of the continually-operating draws, and Omega Man occasionally going out to turn off the lights in other buildings, and I would expect power consumption to plummet. In fact, I even wonder if it would be possible for most plants to handle a demand that low (possibly as low as a single person's consumption). How would this change the situation?

[Gangster Octopus]

CChronos on the correct track. The electricity system would fail almost certainly do to a failure in the transmission system from a drop in demand well before any of the power plants stopped operating. The demand would plummet, while the power plants continue to produce electricity sending tons of power through the wires with no where for it to go. This would essentially cause the grid to fail and then the power plants would automatically trip off at that point.

[BubbaDog]

Re:Demand

There is a little wiggle room in there for demand. While there are a number of other things that can go wrong most systems (control areas) of generators are controlled via a central control point (control center) and these control centers send load changing signals to the power plants.

So as long as the automatic programming at the control center is working the signals will be sent to the power plants to increase or decrease the flow of fuel into the pland and therfore the generators will meet the demand.

Now if the Zombies got into the control centers...........

[BubbaDog]

inadvertant smilie

Re:....Demand

[Una Persson]

Erm, would that work? I thought gasoline goes "stale" after a couple months or so?
Gasoline can lose volatility and go "stale" after some time - the actual time depends a lot on storage conditions, temperature, etc. However, it still remains burnable for some time, it's just not in ideal condition for doing so. I've personally seen 15-year old gasoline stored in a steel tank be able to start up a car, so I figure with good quality tanks and cool temperatures (and enough supply) one could likely keep home generators running. If the generator gums up, just haul it out back and unpack another one.

Remember too that I'm assuming that you only need the generators for a few years - the zombies will get you, no matter what. One say you'll let your guard down, or get careless, or get cocky, or try "making friends" or "embracing diversity", and then...chomp.

[Una Persson]

And what about decreased demand? At the very least, sudden zombification seems to predominantly occur at night, so one would expect demand to be frozen at nighttime levels. Add in power draws which require continuous human attention, zombie-induced damage tosome of the continually-operating draws, and Omega Man occasionally going out to turn off the lights in other buildings, and I would expect power consumption to plummet. In fact, I even wonder if it would be possible for most plants to handle a demand that low (possibly as low as a single person's consumption). How would this change the situation?
Well, if it happens at night then the plants are already turned down to nighttime loadings when it happens. Gas turbines can run at fairly low loads for long periods of time, and even some (but not most) coal plants can have stable operation down at 40%-50% load. I'm uncertain about long-term nuclear low-load operation.

I mean, we're kind of talking serious hypotheticals here about how a mass zombification actually goes about. If we say at midnight the process happens, it's possible by my research and estimates that by morning (7:00 am) several plants have fallen, or at a minimum not started load ramp up. But ones which are able to continue are already at the reduced load...I guess the actualities can be envisioned many different ways.

[Una Persson]

Being a coal fired plant, he told the non-zombie guy his new job would be to turn out a dozen ash, sulpher, and mineral content reports a day (typed—remember no desktop pc’s then) involving samples of coal for the boilers for the next 12 months. (Question: did non-zombie guy become a zombie at that point?)
Eh. I've done worse jobs and I'm still not...oh wait, the brain eating. Yeah.

From whatever else I can remember, my cousin said it took normally about 30 minutes for the turbine to coast to a stop (is it really that long?).
Generally you want the steam turbine to come to a stop gradually to allow it to cool down slowly and evenly without risk of warping. While this spindown process is happening you need the lubrication pumps to be flowing both for a fresh supply of oil and for cooling purposes. Some turbines have small electric motors that keep them turning for some time after shutdown, to allow the turbine to contract and shrink evenly within its housing - I think they are called "pony motors" but would need to look this up or ask...

[Una Persson]

CChronos on the correct track. The electricity system would fail almost certainly do to a failure in the transmission system from a drop in demand well before any of the power plants stopped operating. The demand would plummet, while the power plants continue to produce electricity sending tons of power through the wires with no where for it to go. This would essentially cause the grid to fail and then the power plants would automatically trip off at that point.
Well, I don't know. First, remember I said that within 4-6 hours the blackouts and brownouts would start. If we're talking a midnight zombification, then I'm saying by 4:00 am to 6:00 am we're seeing blackouts and brownouts. So I highly doubt the demand would change that much in that length of time to cause the "grid" to fail before "any" of the power plants stopped.

Second, the "grid" is by no means a homogeneous entity. I recommend reading the report of the Big Northeast Blackout (linked at the bottom of my article) to see some maps and examples of inter-ties and connections and controls. Some parts of it are much more able to cope with load-balancing than others. Just as all plants are quite different and would respond differently to this situation, the different components of the electrical networks would also have different levels of resposne and impact.

Third - if the plants are already running at night-time loads, why would demand change that much? Let's see where a lot of the demand would arise: if it's Winter time, all those people with electric heaters are still going to have their heaters running. Possibly moreso, as the zombies go through windows and leave doors open, causing the thermostats to never reach temperature. Lights (excepting streetlights) that are on will stay on (unless the zombies break them). Few appliances run at night, so no big change might be seen there. Now, the morning industrial/business ramp-up won't happen, but then most of the power plants that are still running are going to still be at their low load values, so... The same situation could be envisioned with Summer and air conditioning loads as well. But by noon most likely so many plants are down that most portions of the grid have failed anyhow.

As I said to Chronos, we're talking some hypothetical situations here that have a wide level of variance on them, so we can't really say what happens.

[Mycroft H.]

I mean, we're kind of talking serious hypotheticals here about how a mass zombification actually goes about.

But surely there is experiential data from someplace regarding this phenomenon? From Transylvania or someplace? Or perhaps some computer simulations based on a doctoral thesis or Pentagon Wargame scenario? I mean this is important stuff!

Una, wow, once again you have done an incredible job with a staff report. Thank you for educating the ignorant. You are so cool I may have to start an Una-appreciation thread. (And no, this is not an attempt at flirting.)

[Gangster Octopus]

Re:Demand

There is a little wiggle room in there for demand. While there are a number of other things that can go wrong most systems (control areas) of generators are controlled via a central control point (control center) and these control centers send load changing signals to the power plants.

So as long as the automatic programming at the control center is working the signals will be sent to the power plants to increase or decrease the flow of fuel into the pland and therfore the generators will meet the demand.

Now if the Zombies got into the control centers...........

It really depends on if and how much demand decreased, because a sudden drop in demand could not be quickly met by available resources, since most coal and gas generation requires time to ramp up or down it's production. Most system operators have complex computer models that attempt to anticipate the load changes,but drastic changes can have calamitous effects.

I agree with Una that if the zombification happened at 2 or 3 in the morning (the minimum load times for most areas) then there would probably be little demand effect, compared to other times of the day. I guess the onlypoint I was trying to make was that it is not just the abiliuty of the generators to make electricity but the ability of the zombies to consume electricity as well as the zombie world to maintain the balance between the two that would determine the fate of the system.

[BubbaDog]

Some turbines have small electric motors that keep them turning for some time after shutdown, to allow the turbine to contract and shrink evenly within its housing - I think they are called "pony motors" but would need to look this up or ask...

Way too many years ago I remember visiting a GE turbine manufacturing plant in Schenectady. I seem to remember them pointing out a turning gear or something on a large 700 MW turbine which was used to slowly rotate the turbine rotor when the generator was off the grid.

IIRC the reason for turning the rotor was that it weighed so much it would warp itself under its own weight if left in one position for too long. So I imagine that if there was a concern over a cooled turbine warping there must surely be a need to continue turning a warm one.

I've pretty much forgotten a lot of the rest of it since after the tour the GE rep used his liquor expense account to erase my memory.

[Una Persson]

Way too many years ago I remember visiting a GE turbine manufacturing plant in Schenectady. I seem to remember them pointing out a turning gear or something on a large 700 MW turbine which was used to slowly rotate the turbine rotor when the generator was off the grid.

IIRC the reason for turning the rotor was that it weighed so much it would warp itself under its own weight if left in one position for too long. So I imagine that if there was a concern over a cooled turbine warping there must surely be a need to continue turning a warm one.
I've seen and heard that explanation before, but then the turbine does stay stationary for months sometimes whilst it's undergoing a major overhaul, routine maintenance, being rebuilt or rebladed...so I'm not certain what the difference would be necessarily. But I'm no turbine expert, so perhaps someone from that field can join in and edumacate us.

I've pretty much forgotten a lot of the rest of it since after the tour the GE rep used his liquor expense account to erase my memory.
So, he tried to turn you into a mindless check-signing zombie... ;) Oh yes, I've had plenty of reps try to do that to me, for one reason or another, especially when I'm in the Former East Bloc. And they won't take "no" for an answer unless I fall on the "diabetes" excuse to stay with Diet Coke or water.

[BubbaDog]

It really depends on if and how much demand decreased, because a sudden drop in demand could not be quickly met by available resources, since most coal and gas generation requires time to ramp up or down it's production. Most system operators have complex computer models that attempt to anticipate the load changes,but drastic changes can have calamitous effects.


But Ganster sudden load drops happen all the time and the systems respond usually befor the operators do.

Now a widespread and severe sudden load drop might do it but it would take organized zombies to do that.

:p

Nobody ever said the zombies were organized

[Una Persson]

Una, wow, once again you have done an incredible job with a staff report. Thank you for educating the ignorant. You are so cool I may have to start an Una-appreciation thread. (And no, this is not an attempt at flirting.)
Well, thank you very much. It's just an area I know a bit about*, and have a bit of experience in, so I wanted to try to make a comprehensive article that was still readable.



*Power plants, not zombies. I need to learn more about zombies. Who doesn't need to, after all?

[BubbaDog]

On my staff are two engineers who spent a few years in power plants.

Their comments

Pony - familiar with the term. Usually heard it referenced with a startup assist motor but don't disagree with the term used as una described..

turning gear - generator rotors spin at very high speeds so even a very slight sag in the rotor is serious. Turning gears very slowly and constantly turn rotors. Since rotors must be stationary occasionally they must be turned for a prescribed length of time following the still period. One of my guys said that after an outage requiring a still rotor they would probably turn the rotor for a few days until it would sag back to equilibrium.

zombies - work in coal power plants and drink lots of coffee

[Rico]

Not much to add here but WOW.

Great report, Una! I loved the union-non-union line.

But a question: Would non-union zombies be scabs?

:smack:

:p

[Lemur866]

Una, thank you for this report.

The tireless efforts of you power engineers to keep us supplied with electricity during this unfortunate zombie plague are greatly appreciated.

[hibernicus]

On my staff are two engineers who spent a few years in power plants.

Their comments

Pony - familiar with the term. Usually heard it referenced with a startup assist motor but don't disagree with the term used as una described..

turning gear - generator rotors spin at very high speeds so even a very slight sag in the rotor is serious. Turning gears very slowly and constantly turn rotors. Since rotors must be stationary occasionally they must be turned for a prescribed length of time following the still period. One of my guys said that after an outage requiring a still rotor they would probably turn the rotor for a few days until it would sag back to equilibrium.

zombies - work in coal power plants and drink lots of coffee

Over here, we call it the "barring gear". Maybe it's a regional thing.

I'm thinking that if you left the open cycle gas turbines running at low-load (typically in diffusion rather than pre-mix mode) the EPA zombies would come and shut you down for producing excessive NOx.

Una, that's a brilliantly entertaining Staff Report. Thank you!
:cool:

[si_blakely]

I remember being told (as a kid) about the geothermal turbine at our local Paper Mill (Kawerau, New Zealand).

The pony did not disengage as the turbine spun up, and the motor disintegrated as the turbine reached operating speed.

The image of shattered motor casing and splayed out rotors have stayed with me for life.

Si

[DDX2k2]

Great article. I have no engineering background, but it occurred to me that while it might look like hydro dams might be the longest lasting source of power, one if zombies attack in spring and the operators are zombified or on the run, who'll open the spillways to relieve pressure on the dam (or, to maintain water)?

In quick zombification scenarios, the turbines and water flow would stay right where they were when zombies arose - this could let most of the reservoir drain or, if little or no water was flowing at the time, let water build up, possibly leading to a big problem. I don't think most dams are designed to have water going over the top of them.

[gregjsmith]

This was very interesting. However I think equally important is what happens after the power plants shut down? Do nuclear plants meltdown (irradiating and mutating the zombies), do coal plants start emitting toxic chemicals (mutating the zombies), Do long shut down hydro plants dams fail with cracks and flood the valleys before them?

[Una Persson]

Great article. I have no engineering background, but it occurred to me that while it might look like hydro dams might be the longest lasting source of power, one if zombies attack in spring and the operators are zombified or on the run, who'll open the spillways to relieve pressure on the dam (or, to maintain water)?

In quick zombification scenarios, the turbines and water flow would stay right where they were when zombies arose - this could let most of the reservoir drain or, if little or no water was flowing at the time, let water build up, possibly leading to a big problem. I don't think most dams are designed to have water going over the top of them.
Thank you for reading. You are correct in saying that most dams are not designed to have water going over them. In fact, according to the hydro guy I talked to today, water going over the top is considered to be a "worst case scenario". I asked him if dam failure wasn't in fact the worst case scenario, and he modified it by saying "second worst-case".

He did say that many dams do have "emergency" spillways that are always open at or near the top, but that some dams do not have this. It depends a lot on the type. So there is a possibility that a dam or three could have a serious failure without human intervention, provided that there are no functioning automated or passive controls to prevent such a thing.

[Una Persson]

This was very interesting. However I think equally important is what happens after the power plants shut down? Do nuclear plants meltdown (irradiating and mutating the zombies), do coal plants start emitting toxic chemicals (mutating the zombies), Do long shut down hydro plants dams fail with cracks and flood the valleys before them?
I can't speak for nuclear plants. Gas plants are unlikely to have a serious problem, barring possible leaks if the pipes break or corrode through. Coal plants would be similarly benign. Unless, of course, the gas or coal plant had a large amount of ammonia on-site for NOx control of some sort (SCR or SNCR system), in which case down the road there is the potential for a large ammonia leak. How bad this is depends on the type of ammonia and quantity. Aside from this - the coal pile will very slowly degrade and become soil, and most items in the plant will rust/collapse into a large heap of metal.

Hydro plants will fail, eventually, but the process could take decades or longer, depending. By that time maybe the zombies will have evolved enough to learn to take care of the plants, and even restore electricity. Who knows - perhaps in some far distant age they may even be able to figure out how to keep their VCRs from flashing "12:00" at them all day.

[Gorsnak]

Who knows - perhaps in some far distant age they may even be able to figure out how to keep their VCRs from flashing "12:00" at them all day.
I should think they'd achieve this laudable goal just as soon as they managed to wipe out the power grid. :)

[jason_mc99]

Hey Una,

That was my question! Thanks for answering it so well - great job! I enjoyed it immensely.

[tracer]

Gasoline can lose volatility and go "stale" after some time - the actual time depends a lot on storage conditions, temperature, etc.
I've seen something in an auto parts store called "Sta-Bil", which is supposed to "stabilize" gasoline so that it'll last a lot longer before it "goes bad."

Does this stuff actually make a difference, or is the company that makes it relying on the fact that most gasoline will last a long time without treatment anyway?

[Una Persson]

Hey Una,

That was my question! Thanks for answering it so well - great job! I enjoyed it immensely.
You're welcome, and please take a look around the SDMB while you're here. You can get the answers to all life's questions...

I should think they'd achieve this laudable goal just as soon as they managed to wipe out the power grid.
Yeeesss...zombies are a clever lot...

I've seen something in an auto parts store called "Sta-Bil", which is supposed to "stabilize" gasoline so that it'll last a lot longer before it "goes bad."

Does this stuff actually make a difference, or is the company that makes it relying on the fact that most gasoline will last a long time without treatment anyway?
Sadly, I have no experience with that. Maybe someone else has tried it.

[Mysticeti]

Authors often do a lot of research before writing their novels and a couple really good stories come to mind...

The Stand by Steven King. No zombies but society does brake down and the power does go out. Lots of detail on what some survivors have to do to get a plant back on line (including shutting off all the clothes driers in the laudrymat to keep load down).

Lucifer's Hammer by Larry Niven and Jerry Pournelle. Again no zombies but mass de-population via other means. Includes an almost epic battle to keep the juice running at a nuke plant.

Possibly nothing but pure fiction but entertaining none the less.

Anyone know much truth there is in these plot lines?

[BubbaDog]

The Stand by Steven King. No zombies but society does brake down and the power does go out. Lots of detail on what some survivors have to do to get a plant back on line (including shutting off all the clothes driers in the laudrymat to keep load down).

Anyone know much truth there is in these plot lines?

Bolding Mine

I haven't read The Stand but during a recovery it makes more sense to disconnect sections of the power grid instead of trying to find and turn off appliances connected to the grid.

[grg88]

The electricity system would fail almost certainly do to a failure in the transmission system from a drop in demand well before any of the power plants stopped operating.

The demand would plummet, while the power plants continue to produce electricity sending tons of power through the wires with no where for it to go. This would essentially cause the grid to fail and then the power plants would automatically trip off at that point.

Not quite right. If demand drops the electricity doesnt get produced with no place to go-- the generators fell the lessened load and reflect back less mechanical load on the turbine, whose steam regulator turns down the amount of steam going to the turbine in order to maintain the same generator RPM. This adjustment happens automatically and continuously, in much less than a second, as the generator must stay in phase with the reset of the power grid-- it can't be allowed to get even a fraction of a revolution ahead or behind the grid voltage.

The lessened demand for steam eventually shows up as a higher steam pressure in the steam collector manifolds, which is noticed by another automatic system which adjusts the fuel input accordingly. If the steam demand went down very quickly and significantly, there may be too much thermal inertia for this control loop to handle the rising steam pressure, in which case the extra steam must be blown off thru a overpressure valve or dumped through a condensor.

-----

That's for a coal or gas plant. They tend to be able to adjust relatively quickly to


For a nuclear plant things are not so simple. There's about a bazillion different nuclear decay reactions going on at any instant. If the electricity demand drops, it's as above reflected back as decreased demand for steam, which results in higher pressures in the reactor cooling loop, which affects the neutron absorption properties of the coolant. The control systems will try to lower the reaction rate by dropping in more control rods. But the rods cannot control all the decay reactions that are already under way. About 30% of the reactor's heat production is from these secondary decays, which cannot be controlled at all. So even if the electric load goes to zero, there's still about 30% of the reactor heat output that has to be dumped somewhere until the decays, well decay, whcih will be several hours. There's also the curious problem of Xenon poisoning-- Xenon is a decay product that has a very large ability to squelch neutrons. In a stable reactor, the xenon poisoning is kept under control. But if the reactor power goes way down, the xenon poisoning has a chance to peak, making the reactor hard to control. The control algorithms try to keep all these bad things from cascading, but without a little human intelligence in the loop the reactor could easily trip off line.

----
And no, whatever abilities Stephen King has in a literary way, he generally botches anything technical, witness in THe Shining, the curious, unphysical behavior of the furnace and the snowmobiles (not attributable to spooks).