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I'm learning tons of stuff about nuclear physics, nuclear power, nuclear reactors, and their history lately, and I'm finding it fascinating.
This thread is just a place for me to talk about all that stuff with anyone who is interested.
First of all, do you have any questions? I will be glad to research and try to find out anything anyone wants to know.
Secondly, I just read a book on the Chernobyl nuclear disaster. It was written by a Soviet Nuclear Engineer who earlier had worked for a long time at Unit 1 of the Chernobyl station (it was Unit 4 that blew up), and who knew all the people involved. He was sent to the site about 2 weeks after the accident (which happened on 26 April, 1986) to investigate and talk to everyone involved, some of whom died shortly thereafter of the radiation sickness. He wrote a report which is technically excellent, and also excellent from a human standpoint. It was translated into English.
I did have to consult Wikipedia in some cases to understand the technical considerations he brought up. (Wiki has such clear explanations of things!) In some cases it was hard to read. I had to put it aside from time to time because I was tearing my hair out and banging my head on the table reading some of the things they did. But in addition to the horror there is great heroism shown. I'm fascinated by the story. Here is the complete book, of which I've only read a 75 page Notebook so far. I have ordered it from Amazon.
Secondly, I have a question for anyone who knows about nuclear reactors. One of the design flaws of the RBMK reactor design (the type used at Chernobyl) is that it has a high "void coefficient", a property which makes the reactor difficult to control because it introduces positive feedback. In other words, the hotter the reactor gets, the more reactivity it has. I know that the new pebble bed reactors have the opposite quality, that the hotter the core gets, the less reactive it is. I was wondering if this quality, which I think is probably called the core reactivity coefficient, is published for all the different types of reactor designs in existence, and what it is for each of them. Does anyone know? Or can someone with better google-fu than I possess find out? I'd love to know that.
And finally, I want to ask hatrackers, are you pro-nuclear? Do you find it a good thing that we're beginning finally to build new reactors again after a 30 year hiatus? I'm terribly excited about that myself. They emit no greenhouse gases, are cheap, safe, and reliable. They are environmentally friendly. I wonder if others here agree?
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I agree completely, infact the Chinese are in a building spree for nuclear pepple bed reactors and are installing a Fusion Tokomak reactor for experimentation that will utilize both Duetorium and Tirtium. They plan that Fusion will be availiable for commercial use in 50 years.
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I think nuclear has definite benefits, but I don't think it should power the whole world until the problems of nuclear waste can be solved. I've seen a lot of good information from you before Tatiana about newer reactors that eliminate nuclear waste, or at least largely diminishing the problem. I think, when used in conjunction with renewable energies, it's a perfectly safe and reliable energy source, but it shouldn't be the end of our energy journey.
Posts: 21898 | Registered: Nov 2004
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Are we actually building new reactors? I do think it is a shame that we closed functional plants and didn't allow viable plants to start up. That was just stupid.
But I also think that if the reason for building new plants is to allow for an increase in energy use, we're missing the boat. There is no substitute for conservation.
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True that was a design flaw in their core (the Russians), but it actually wasn't that bad of a design. If they had just trusted their indications they would not have had the problem.
I'm not sure where to find it online, but I can say that the US reactors have the opposite of that. As the water gets hotter it sends a negative, less reactive, feedback. Basically allowing the operators to control it in a stable manner.
If wasn't pro-nuclear, I would be out of a job. An' we have been building reactors in the past 30 years. We just weren't building them for commercial use. They power ships, and submarines (I don't know why anyone would want to ride those). Cheap...heh, in the short run, ok. They are environmentally friendly until the point of getting rid of the spent fuel. I say launch it into space and we won't have to worry about it.
Posts: 2208 | Registered: Feb 2004
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quote:Originally posted by Stan the man: I say launch it into space and we won't have to worry about it.
I can't imagine that is going to be cost effective. If you factor the cost of shipping all that dangerous material into space (and the cost of a cleanup if a shipment should explode and dust the earth with radiation), does it become more expensive than the rest? I'm betting it does.
Further, we have no idea what happens to all that material. We could send it ballistic towards the sun, but that has to be even more expensive, but we can't just litter space. We're going to be up there one day, and it's short sighted to start shooting waste out there.
Posts: 21898 | Registered: Nov 2004
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quote:Originally posted by Stan the man: I say launch it into space and we won't have to worry about it.
I can't imagine that is going to be cost effective. If you factor the cost of shipping all that dangerous material into space (and the cost of a cleanup if a shipment should explode and dust the earth with radiation), does it become more expensive than the rest? I'm betting it does.
Further, we have no idea what happens to all that material. We could send it ballistic towards the sun, but that has to be even more expensive, but we can't just litter space. We're going to be up there one day, and it's short sighted to start shooting waste out there.
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Launching it into space is also expencive as it is, what is it 1000$ per pound to launch? And we aren't exactly getting those rockets back either if we wanna make sure they head into the sun.
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Ok, fine. I'll retract the light hearted comment. Sheesh, beats burying it in your backyard. Ah! Iowa! Nobody knows where thats at anyway .
Posts: 2208 | Registered: Feb 2004
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Well, the new fast reactors will burn the wastes of the other reactors as fuel, and extract 94% of the energy (the current designs only use 5%), leaving much less tonnage of wastes to be dealt with, and the waste that IS left is only dangerous for 500 years instead of 10,000. So waste is not going to be a problem long term, I don't believe. I don't think we should bury it in Yucca mountain at all, but simply save it for use as fuel when the new generation of fast neutron reactors is built.
Stan, you're so right that we've been building military reactors for ships and submarines all along! I shouldn't have forgotten that. What is their design? Are they BWRs or PWRs or what? Do they use enriched fuel, or nonenriched like the Canadian CANDU commercial reactors do? Is any of that information public? I'd like to learn more about them.
Posts: 6246 | Registered: Aug 2004
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Tatiana, as far as military, the Navy is the only branch using. The others have tried, but didn't get the research results they wanted. It just wasn't practical for the army/air force.
Yeah, I haven't been reading up on the new fast ones as much. I read about them when they initailly designed the concept, but I've been quite busy since then.
As far as learning more about...not really any source online for it, and I can't go too far into details. We still use the safe PWRs, but we spend the extra money to enrich the fuel. It gives us a longer life span of reactor. Canada is not the only ones to use non-enriched fuel, even the US commercial plants use non-enriched fuel.
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Are they using the same reactors in the new, smaller carriers that are of the next generation that they used in the last class of supercarriers?
Or did they design something smaller?
Posts: 21898 | Registered: Nov 2004
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We have a new design coming out (both ship and reactor), but we don't have all the technology to make it work yet. It'll only be a couple more years.
Yep, I'm gonna miss those ships when they go. I love'em. Good thing they'll be around for a while. Although, I might still be alive when they decom my last ship. I'll be about 80 years old.
Posts: 2208 | Registered: Feb 2004
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Interesting about the Navy using PWRs. All the newest commercial reactors in the U.S. are also PWRs, I think. The EPR is also a PWR, but a cool new design about which I've not been able to find very much.
Stan I read that the U.S. commercial reactors are all BWRs and PWRs. I thought those both used only enriched fuel. Are there commercial plants in the U.S. using non-enriched?
I know that PWRs have about 1/3 the maintenance costs of the BWRs, mostly because PWRs have a lot less stuff that's radioactive in the plant. In BWRs the turbines and everything are exposed to the radioactivity of the primary cooling loop of the reactor vessel. I was wondering if another reason the PWR design was preferred now over the BWR is because of any possible difference in reactivity coefficients between them. So far I can't either confirm or eliminate that guess, from what I've read. Do you know the answer?
Posts: 6246 | Registered: Aug 2004
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I thought they used non-enriched, but I could be wrong. I've only been to one of them.
PWR vs BWR: I would have to look that up myself as well. I don't know the reactivity affects that go into their design.
Posts: 2208 | Registered: Feb 2004
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Shoot, I remember now. I was thinking that non-enriched was a factor in the short life of commercial plants. I forgot that they raise their rods all the way to the top when they put them online.
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I should define PWR and BWR, for the benefit of anyone who doesn't know. A Pressurized Water Reactor (PWR), cools the core with water that is kept under pressure and not allowed to boil. It then goes to the Steam Generator, a heat exchanger which makes steam in a secondary loop to send to the turbines.
A Boiling Water Reactor (BWR) is an older design. Cooling water is allowed to boil in the core, and goes as steam directly to spin the turbines (which spin the generator which makes electricity). From there, the steam goes to a condenser and is pumped as liquid water back to the core. The advantage is that the primary loop is at normal atmospheric pressure, so doesn't tend to develop leaks as easily. The disadvantage is that more of the plant gets radioactive, including turbines, piping, etc. In a BWR plant there will be many more radiation controlled areas that require protective clothing, dosimeters, decontamination, etc. to visit for maintenance, than exist in a PWR plant.
Posts: 6246 | Registered: Aug 2004
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I'm in favor of developing more nuclear power plants, as long as they are not in MY back yard.
Because, honestly, it is a small back yard, and if we put a nuclear power plant there, there wouldn't be enough room left for my sukkah.
(I need to customize this spellchecker! It keeps trying to suggest substitutions for words not in its meager vocabulary. "room left for my suck", indeed!)
Posts: 10397 | Registered: Jun 2005
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There aren't too many BWR's left these days. I know Michigan has one BWR and two PWR's. When I get out, I might look at getting a job at one. However, after 7 years, I'm tired of someone always looking over my shoulders. I don't want to do the same thing as a civilian and have to deal with the same thing. Unless I get paid enough.
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Yeah, and now mine knows the word "Sukkah". But it would be nice if the 'checker's vocabulary matched mine, instead of suggesting ridiculous substitutions.
Like "shipping nachos" for "shepping naches".
Why in the world would I tell someone that they should only ship nachos over their children?
Posts: 10397 | Registered: Jun 2005
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Tatiana, is it true that coal plants release more radioactivity per watt of power generated than nuclear plants, because of Carbon-14 released into the atmosphere from coal plant emissions?
A friend told me shortly after the Chernobyl accident that the Russians shot one or more of the people in charge of the reactor for incompetence, but the wiki page has no mention of this. Did that happen?
Posts: 6316 | Registered: Jun 2003
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One aspect that should not be forgotten is that with increased usage of nuclear power around the globe more enriched fissionable material will be in circulation, increasing the risk of nuclear weapons being built or acquired by "undesirable elements". Compare current concerns about Iran's nuclear program working as a cover for weapons developement.
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Morbo, it's hard to answer your first question. I think on a normal day that it's true, that coal fired plants release more. However, how do you factor in days like April 26, 1986 into the equation? It's reasonable to expect, for a number of good reasons, that nothing so bad will ever happen again, but it definitely happened once. I think we'd have to say that nuclear plants have in the past emitted more radiation, though in the future, there are good reasons to believe they will emit less. I will research and find more particulars about particulates this weekend.
The book I read said that several of those in the chain of command were fired from their jobs and kicked out of the party. It says nothing about anyone being shot. The ones most immediately responsible for causing the accident (those who carried out the test that precipitated it) mostly died of radiation exposure, including the operator who first refused to do what he was told, and his boss who ordered him to do it anyway, and managed to cow him into submission from fear of being fired. I have to say that even the ones who were criminally stupid enough to have caused the accident were heroically brave in the aftermath. It could have been so much worse had they not taken some of the actions they did, and with no regard for their own safety. They sacrificed their lives. I feel for them a mixture of great admiration and great sadness.
Remember, everyone who works for a boss, when they tell you to do something life threatening, refuse, and don't let yourself be bullied. Being fired is better than being dead. If you are calm about it, you're doing the world a service (even if you don't work in an industry where the results could harm a lot of people). And in the end if you do get fired, you're better off.
Posts: 6246 | Registered: Aug 2004
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After it happens, nuclear accidents are no longer probablities but realities, so you have to factor that in. But don't exert yourself, the answer that on normal days you agree that coal releases more satisfies me. A SF writer said that years ago, and I have wondered about it.
I guess my friend was wrong about people being executed for Chernobyl.
Posts: 6316 | Registered: Jun 2003
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He could be right. I just don't have that information. Mother Nature definitely executed those immediately responsible, dealing out her age-old summary punishment for ignorance. However, among the higher ups, for instance, the ones who shoved through impossible construction deadlines, and strict production schedules, I'm not so sure.
It could be argued that Chernobyl was one of the main factors that caused the breakup of the former Soviet Union. The incompetence and lying were possibly beyond what even the Russian people could tolerate. (Of course, it was Ukraine and Belorus who took the most damage, not Russia.) I do believe the bad faith the attempted coverup of Chernobyl showed was enough to bring down the Soviet government. (I just wish our own government today didn't remind me so strongly of the Soviets then, for instance, the FEMA debacle over Katrina. )
Posts: 6246 | Registered: Aug 2004
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quote:Originally posted by HollowEarth: Have you looked at liquid metal cooled plants yet?
HE, the new fast neutron reactors are all liquid metal cooled. They have to have a coolant that doesn't slow down neutrons the way water tends to do. As far as I know, liquid sodium is the coolant that they almost all use. I'm not to thrilled about that choice because it is quite flammable in the presence of oxygen. Not a problem on a normal day, but on a very bad day, it would be unfelicitous.
The reactor at Chernobyl used graphite for moderation, which of course is also rather flammable. The graphite fire in the core burned for nine days, I think, before they could put it out. During all that time, the core was releasing a plume of radioactive gases and particles into the atmosphere. It would be great if there were a suitable liquid metal which was not so flammable as sodium. Though we can feel a pretty high confidence that there won't be another Chernobyl (the state of the art is so much better now), I read that there has already been a sodium fire associated with a coolant leak or spill at one of the sodium cooled reactors. Their fire safety system put it out before it caused much damage.
I guess there are a lot of considerations for the core coolant, including how transparent it is to neutrons, how toxic it is to handle, what its melting temperature is (how likely it is to solidify and plug the pipes), and how expensive and easy to get. It may be that there are a lot of reasons why sodium is simply the best choice for coolant.
I'm really interested in the liquid metal cooled designs in general, though, since I think they're going to be the way of the future. They are able to burn the waste of the other reactor types, as well as tailings from uranium mines. We will need no more fuel for them than what we already have available in those forms, without additional mining, for the forseeable future.
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I'm learning a lot more about the systems for BWRs and PWRs and it's really interesting how they work. I'm in the second week of a four week school right now, and one of the topics we covered is all the different emergency core cooling systems there are in the event of a loss of the main reactor coolant system.
There are three systems of completely different design for emergency core cooling, and each of the systems has entire redundant trains of inlets, pumps, injectors, etc. so that if something goes down there's always a backup and a backup to the backup, and so on. It's really interesting! I can't wait to actually go on site to one of the plants. I wish Samuel Bush would come back so I could ask him about the difference between fossil plants and nuclear. I understand for fossil, they superheat their steam a whole lot more, and their turbines turn at 3600 rpm instead of 1800 like ours.
The most fascinating thing to me is to find out why something is done the way it is. Sometimes our instructor doesn't know, but there are always people scattered throughout every class who have been working with the systems for a long time, and they know so much, it's really great to be able to hear from them and learn from their knowledge. There's almost always someone in class who knows the answer to any question anyone can come up with.
For instance, I asked the queston why does the nuclear plant use steam at a lower temperature than fossil. The answer turns out to be that the reactor vessel is fairly small compared to a fossil boiler. Obviously, because it's a pressure vessel and becomes highly radioactive, you want to keep its size to a minimum to keep costs down. There need to be few or no moving parts inside, because maintenance in there is very expensive. The fossil plants have lots of room to run their steam lines through the boiler again and again. The reactor vessel, however, is only really big enough to allow the lines to go through once.
And though fossil operate at such a higher temperature, nuclear is much cheaper per kilowatt hour to generate. That's because nuclear's fuel costs are far less.
Posts: 6246 | Registered: Aug 2004
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quote:Originally posted by Lyrhawn: We could send it ballistic towards the sun, but that has to be even more expensive, but we can't just litter space.
That's always my answer when someone posses as question about waste management (nuclear or your run of the mill non-biodegradable trash). Sure it's not very cost effective NOW, but we can make some room for it here on Earth for 50-100 years until it is easy and cost effective to launch it into the sun.
Posts: 879 | Registered: Apr 2005
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Didn't have time to read the thread, but I saw the word Chernobyl and thought immediately of Chernobyl girl.
Posts: 1209 | Registered: Dec 2003
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human_2.0, I love that site! I told everyone at work about it. Many had already encountered it. I am fascinated by nuclear accidents and want to understand every detail of what happened, so that I can make sure to recognize those factors and avoid them.
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I found out a whole lot more about core reactivity coefficients, and they are a lot more complicated than I thought. It's not just a single number for each reactor type, but varies according to the age of the fuel, the amount of boration in the coolant (for a PWR), the amount of burnable poisons that are currently in the fuel (isotopes added to extend the time between refueling outages), the temperature of the coolant and fuel, and so on.
It is comforting that these reactivity coefficients are always kept negative in BWRs and PWRs (meaning the core becomes less reactive with rising tempeture, tending to limit any reactivity excursions). In the few configurations where they have a possibility of being positive (meaning the core would become more reactive with rising temperature or flux) there are operational rules that prevent that from happening.
I'm done with the four week overview of fundamentals now, and my next school will be PWR systems in July. That's supposed to be much more intense. I am having such a great time actually being taught the things I need to know about the machinery I'm working on. That's never happened to me before. Always they've sort of thrown us at the things and let us learn on the job (in other industries besides nuclear). I'm really happy about the courses we've had so far. I hope I can remember everything I'm learning.
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