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Fast breeders are known for decades now, and in some let's just say more nuclear-advanced countries are already used commercially. They can operate on a nuclear waste as a fuel, killing two birds with one stone - using up piles of nuclear waste accumulated all over the world, and creating essentially free energy at the same time! Due to all that nuclear hysteria Germany has falled far behind in the nuclear tech. But the future of humanity is in nuclear energy, whether some people like it or not, as no other power source can provide enough energy for our ever-expanding needs.
I know, forgot to mention them, an oversight on my part. You are quite right. The comment was meant to address the mentality of "most current reactors use X, I only have a century's worth* X in my cupboard, therefore it's madness to build new reactors in case X gets expensive" rather than the details.
* - illustrative number. -
Actually, I had decided not to discuss this topic anymore. Having worked in the nuclear sector in Germany, I know the industry and the German plants quite well. The amount of irrationality in this discussion is only making my stomach churn and I've had enough gray hairs from this. What you get to hear even from people with an engineering background is not always easy to take.
What makes all this particularly deplorable is that the German DWR 1300 and Konvoi plants designed by KWU were far ahead of its time, especially in terms of engineered safety features and I&C (instrumentation and control), and only current designs like the EPR draw level in this aspect (you've got to know that 25 yeas is a short period in this industry). Operational experience is excellent. A whole bunch of disturbances and difficulties the industry constantly deals with with abroad has been avoided through good design and also a fortunate choice of materials (the other day I've heard that they run "leak management programs" in the US ...). The plants have excellent controllability for a large-scale (1450 MW gross) power plant, and can do power gradients up to 150 MW/min from zero to full load (although some restrictions may apply in some operational regimes), all at the push of a single button. They were always designed to do load-following operation, and also did that on a regular basis.
But let them turn off this crap. It seems that this technology is too sophisticated for the country's soul. I'm done with this. Sorry for getting emotional over this.Frankly, I agree with the stance that the actually existing nuclear power plants are pressurized water reactor or scrubber reactor, so they have inherent security risks in case of danger.
This is partly due to the military in the cold war, that wanted reactor types that could provide them with material for bombs. Other types of reactor (Thorium types) are probably way less dangerous in case of an accident.
"Scrubber Reactor"? But no. Pressurized water reactors as well as boiling water reactors are very ill-suited to breed weapons grade material, mainly because their fuel assemblies cannot be removed during operation. For that purpose, pressure tube reactors are much better, like RBMK or Candu, when we talk about commercial designs.BEven if they would now want to extend the life-time for the few remaining German reactors, it would now take quite some time for a major revision and maininance and also to get new fuel. So they would be down for 1-2 years anyway. In hind-sight it may have been better to keep the reactors running for longer, but that decision point was some 5-10 years ago. All plans are made to shut them down. Already the last extension was only with reduced power, as the fuel was essentially used up.
Yep, an at this point an outage would be unavoidable for refueling and maintenance in all remaining plants. In the longer run, staffing is becoming more and more of a problem. Of course, there has not been much junior staff in recent years, and training someone to become a shift supervisor or reactor operator takes time.1) When not running the reactors 24/7, but shut down in times of low demand, the already high costs additionally go up. A limited power (like 25%) to run near 24/7 is not such an issue, but this still leaves a large part to come from other source.
The provision of balancing power and other grid system services is paid well.2) Having many reactors of the same / similar type is a risky situation. The safety concepts usually call a prompt shut down if a problem with the design is found (e.g. like with the BWRs in Fukushima). Taking safety serious may than cause a black out. So one has to choose between safe or dependable. Given the hard choices and reaction after Fukushima (delaying safety upgrades to keep the reacrtor running) one can not really trust the promissed safety.
You are mixing up design problems with incidents during operation, which may or may not require a reactor trip. Yes, the Fukushima plants had some very basic design deficiencies, with problems at several levels, including the national nuclear regulator, although I do not see that safety was sacrificed in order to avoid a blackout in Japan. Actually, the KWU plants are famous for its low number of reactor trips (some plants in the country had no unplanned trip in 20 years).3) For a world wide large scale expansion of nuclear power the uranium reserves get critical and the fuel would get more expensive. It would at least need reprocessing of used fuel and this did not work out economically.
I'm not an economist but from what I know the percentage of the fuel cost is a low one digit figure of the total operational cost of a NPP. So this is not really a factor, and also the reason why reprocessing and breeder reactors were not economically interesting to this date. -
Yes, mined uranium is a relatively small cost of the plant lifecycle but the processing, enrichment, and disposal of nuclear waste end up making fuelling a very significant cost (anywhere from an eight to a third of the LCOE depending on which "side" prepares the figures).3) For a world wide large scale expansion of nuclear power the uranium reserves get critical and the fuel would get more expensive. It would at least need reprocessing of used fuel and this did not work out economically.
I'm not an economist but from what I know the percentage of the fuel cost is a low one digit figure of the total operational cost of a NPP. So this is not really a factor, and also the reason why reprocessing and breeder reactors were not economically interesting to this date. -
Something I have always wondered about but not looked into is since the spent fuel is still active enough that it has to be kept cool, clearly there is still potential energy there so why can't it be put to use?
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Something I have always wondered about but not looked into is since the spent fuel is still active enough that it has to be kept cool, clearly there is still potential energy there so why can't it be put to use?
Nuclear reactors are finicky/metastable and only use a small percentage of the "available" energy in the fuel. It gets into the specifics of the particular fuel cycles, a starting point for you:
https://en.wikipedia.org/wiki/Neutron_poison -
Building new nuclear power plants makes relatively limited sense.
This. It's worth noting the Finnish Olkiluoto 3, which now seems kinda-sorta operational (!!!), after being 12 years late, is now the most expensive building in the whole human history; a total political disaster.
Extending the permits for old plants also comes with risks; you can't do it indefinitely.
However, Germany has had to make the choice between fossils and nuclear during the transition time to more sustainable energy policy (with the final target of using neither). The correct answer is to use sensible mix of both, on case-by-case basis. What Germany has done is use the most politically unstable forms of fossil fuels (specifically Putin's fart, which also did not come for free but required actual investments in the pipeline, there is no free lunch), and accelerate the transition away from nuclear as fast as possible. This is not sensible; it's politics driven by something else than factual analysis of what would be best for the country (and EU as a whole, too) in the long run.
The advantage of fossil fuel is, the downsides average out. Their CO2, SO2, particulates etc. average; the less you use them, the smaller the problem. Therefore supplementing uncertain renewable production with fossil fuels is not a huge problem. Political risk more than averages out; halve the use of fossil fuels, and the risk is practically totally gone as you can choose where to buy from.
But by closing the NPPs at higher-than-natural rate, Germany has had to keep the fossil fuel use relatively constant; advances in renewables have been directly removed from nuclear, not 50:50 from nuclear + fossils. -
The key word being political - the incompetence of administrations is an argument against politicians, imbecilic project management and copious amounts of bureaucracy rather than nuclear as a concept. In Slovakia we too had some major delays, but again, that speaks of politics and state project management rather than nuclear.Building new nuclear power plants makes relatively limited sense.
This. It's worth noting the Finnish Olkiluoto 3, which now seems kinda-sorta operational (!!!), after being 12 years late, is now the most expensive building in the whole human history; a total political disaster.
Basically what I'm seeing here is an attitude of giving up on big projects the sort of that were done in the past with enthusiasm and looking forward. Instead we are creating overpriced pathetic workarounds and small not-fixes that can have a label with whatever virtues that the current administration wish to signal slapped on to them. Meanwhile in the background solutions (whether it's infrastructure or heavy industry) from 30-50 years ago are working overtime to compensate for the lack of will to build something new and worthwhile.
If we want to adopt an attitude where we just give up big, ambitious projects as a whole, let's just say it right here and now. And we may as well throw in the towel. -
^^^
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To keep this at a technical level (after all, this is an engineering forum, not a political one):
Nuclear reactors are finicky/metastable
Huh? Commercial reactors are designed to be undermoderated, i.e., an increase in fuel temperature or a reduction in moderator density leads to a power reduction. For this reason, in a PWR, slight variations in power demand up to a few percent do not require any input from power control elements. In fact, I can assure you from first hand experience that you can safely turn off all closed loop reactor power control (actually three control loops in series in a German PWR in normal at-power operation), and it will just sit there without moving (stable equilibrium). BWRs have a bit more complicated unit capacity control systems, because reactor pressure and steam voiding have a pronounced effect on reactivity, so they use a control concept in which the set generator power in part acts directly on the power control elements (recirculation pumps and control rods in a BWR). But still, they are undermoderated by design.Something I have always wondered about but not looked into is since the spent fuel is still active enough that it has to be kept cool, clearly there is still potential energy there so why can't it be put to use?
After a four or five years when the spent fuel assemblies are transferred to dry storage, this is just a couple of kilowatts, i.e., not worthwhile. For example, this storage cask is rated for a maximum of 39 kW total heat load. -
Sounds like an example of short term stability, not a truly stable system hence the careful choice of metastability as a description. Leaving an inherently safe/stable reactor to its own devices usually means a rapid and steady drop in reactivity (for legitimate and well thought out safety reasons) rather than continued stable operation. They are intentionally not stable, and partly because of the fuel becoming unable to sustain fission (despite having not yet used much of the available energy).Nuclear reactors are finicky/metastable
Huh? Commercial reactors are designed to be undermoderated, i.e., an increase in fuel temperature or a reduction in moderator density leads to a power reduction. For this reason, in a PWR, slight variations in power demand up to a few percent do not require any input from power control elements. In fact, I can assure you from first hand experience that you can safely turn off all closed loop reactor power control (actually three control loops in series in a German PWR in normal at-power operation), and it will just sit there without moving (stable equilibrium).
Requiring graded/designed loadings of differing fuel elements across the core to be functional is the sort of thing that makes the system finicky. It is not just a case of pouring more fuel in as it gets used up, almost everything about the nuclear fuel cycle needs really carefully designed processes to maintain operation.
You've gone off and talked around the original question like a true politician/industry spokesperson:
Someone asks about energy, so subtly direct the discussion to power....Something I have always wondered about but not looked into is since the spent fuel is still active enough that it has to be kept cool, clearly there is still potential energy there so why can't it be put to use?
After a four or five years when the spent fuel assemblies are transferred to dry storage, this is just a couple of kilowatts, i.e., not worthwhile. For example, this storage cask is rated for a maximum of 39 kW total heat load.
The answer is complex and multifaceted, but it is true that very very little of the available nuclear energy is used in current fuel cycles.Something I have always wondered about but not looked into is since the spent fuel is still active enough that it has to be kept cool, clearly there is still potential energy there so why can't it be put to use?
Nuclear reactors are finicky/metastable and only use a small percentage of the "available" energy in the fuel. It gets into the specifics of the particular fuel cycles -
[Sounds like an example of short term stability, not a truly stable system hence the careful choice of metastability as a description. Leaving an inherently safe/stable reactor to its own devices usually means a rapid and steady drop in reactivity (for legitimate and well thought out safety reasons) rather than continued stable operation. They are intentionally not stable, and partly because of the fuel becoming unable to sustain fission (despite having not yet used much of the available energy).
True, you have to compensate fuel burn-up by adding reactivity over the course of a fueling cycle to maintain power, which is normally about one year. Unfortunately, a NPP is not a perpetuum mobile. The fact that burn-up does tend to decrease reactor power is not a safety feature though, it is much too slow for that purpose. Burn-up runs on quite a different time scale than short term variations in power demand, which the reactor is designed to compensate without control input (at least to some extent, i.e., a couple of percent, as mentioned above). Yes, this is by design. There are reactor concepts which do not have this property.
If you want to make up your own terminology and call this situation metastable or finicky, I'm not going to argue about that. I've never heard this term in this context though.
Someone asks about energy, so subtly direct the discussion to power....
If I understood him correctly, user james_s was asking whether it is feasible to use the heat generated by spent fuel. The answer is no, because of the low heat output (i.e., power).The answer is complex and multifaceted, but it is true that very very little of the available nuclear energy is used in current fuel cycles.
True, and I don't think I've disputed that. -
Actually, I had decided not to discuss this topic anymore. Having worked in the nuclear sector in Germany, I know the industry and the German plants quite well. The amount of irrationality in this discussion is only making my stomach churn and I've had enough gray hairs from this. What you get to hear even from people with an engineering background is not always easy to take.
What makes all this particularly deplorable is that the German DWR 1300 and Konvoi plants designed by KWU were far ahead of its time, especially in terms of engineered safety features and I&C (instrumentation and control), and only current designs like the EPR draw level in this aspect (you've got to know that 25 yeas is a short period in this industry). Operational experience is excellent. A whole bunch of disturbances and difficulties the industry constantly deals with with abroad has been avoided through good design and also a fortunate choice of materials (the other day I've heard that they run "leak management programs" in the US ...). The plants have excellent controllability for a large-scale (1450 MW gross) power plant, and can do power gradients up to 150 MW/min from zero to full load (although some restrictions may apply in some operational regimes), all at the push of a single button. They were always designed to do load-following operation, and also did that on a regular basis.
But let them turn off this crap. It seems that this technology is too sophisticated for the country's soul. I'm done with this. Sorry for getting emotional over this.
Thanks for the rare insights!
What do you think, would it be possible to run these plants with the existing (loaded in) fuel rods for a few more months or years even with reduced capacity?
What would it require?
Because as I see it, even from a green anti atom perspective, fuelling up coal plants is a desaster, and I am not sure whether the generally anti nuclear population (with the very good arguments from Kleinstein) is so much for an imminent shutdown. And no I don' belive of those 1000 people asked polls which are literally running Germany these days.
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Actually, I had decided not to discuss this topic anymore. Having worked in the nuclear sector in Germany, I know the industry and the German plants quite well. The amount of irrationality in this discussion is only making my stomach churn and I've had enough gray hairs from this. What you get to hear even from people with an engineering background is not always easy to take.
What makes all this particularly deplorable is that the German DWR 1300 and Konvoi plants designed by KWU were far ahead of its time, especially in terms of engineered safety features and I&C (instrumentation and control), and only current designs like the EPR draw level in this aspect (you've got to know that 25 yeas is a short period in this industry). Operational experience is excellent. A whole bunch of disturbances and difficulties the industry constantly deals with with abroad has been avoided through good design and also a fortunate choice of materials (the other day I've heard that they run "leak management programs" in the US ...). The plants have excellent controllability for a large-scale (1450 MW gross) power plant, and can do power gradients up to 150 MW/min from zero to full load (although some restrictions may apply in some operational regimes), all at the push of a single button. They were always designed to do load-following operation, and also did that on a regular basis.
But let them turn off this crap. It seems that this technology is too sophisticated for the country's soul. I'm done with this. Sorry for getting emotional over this.
Nice summary !
Germany is turning the nuclear power plants off and France is building new nuclear plants and gets EU funding for them because of clean energy.
We have reached idiocracy levels here.
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Germany is turning the nuclear power plants off and France is building new nuclear plants and gets EU funding for them because of clean energy.
Next logical step: dismiss Bundeswehr, because it's too expensive and weapons are bad anyway, and let, well, someone else's army take care of the country's defense. -
What do you think, would it be possible to run these plants with the existing (loaded in) fuel rods for a few more months or years even with reduced capacity?
What would it require?
The three plants currently remaining in at-power operation (Emsland, Neckarwestheim 2 and Isar 2) were originally scheduled to shut down by the end of 2022. So the natural cycle end, where under normal circumstances a refueling outage would be done, was planned to be close to that date. Now it is possible to do what is called stretch-out operation, i.e., to continue generating beyond the natural cycle end, which is what the plants are currently doing. Before entering stretch-out operation, in (I think) two plants the reactor pressure vessel was opened in a short outage and the core was reshuffled and some fuel assemblies were replaced with partially burned fuel assemblies that were stored on-site. Also, some necessary maintenance was done. This was needed keep the plants running at sufficient power during the winter until mid April, which is the new shutdown date agreed by politics. No fresh fuel has been used, though.
Under normal circumstances, stretch-out operation can last for perhaps 80 days, at least from memory I think that's how far the curves in the operations manual for stretch-out operation go. The details depend on the actual core and must be calculated by the plant's physics department on an individual basis. In any case, under stretch-out operation, the full rated power cannot be maintained, and also the load following capability is restricted. What is actually done is that the coolant temperature is decreased, which frees additional reactivity, allowing to increase fuel burn-up.
That means currently there is not much room for continued operation with the present reactor cores and without any refueling, except for perhaps a few days beyond mid April. There may be other operational restrictions, e.g. deferred maintenance, or staff availability, etc., I don't know. -
And how much outage would mean the refuelling? If the aim is to make it work for another 1-2 years? Would the costs, risk or time to do it enormus?
And what if that decision had been made immediately after the government got the results of the studies regarding the possible enlenghtening of the usage of the plants?
If there would be a political will, could it be made economically feasible in a timeframe and for costs that would beat power to gas initiatives (or maybe renewables)during the same time period? -
These plants are designed to operate safely for much more than half a century. It's not that extending the operational life by "a few years" is any problem. It's extension after extension after extension after extension which gradually becomes a problem. AFAIK, this practice is being critiqued in the USA.
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"Yes, Minister" was a documentary, it seems.
Toxic cloud above Poland from coal burning will double its size.
And it's not like the winds are respecting state borders.
Oh, well, whatever keeps the voters happy...
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And how much outage would mean the refuelling? If the aim is to make it work for another 1-2 years? Would the costs, risk or time to do it enormus?
A normal scheduled refueling outage with annual plant revision takes roughly between 10 and 20 days, maybe somewhat longer when particular work is to be done. The thing is that no such outage is planned for. And new fuel is not purchased via online order with same-day delivery. So no idea how long that would take given the current circumstances. But that is surely not a matter of a couple of weeks, even if the political will was there. -
But I mean with the needed maintenance for the few years extra running time. Because for me it is not clear wheter this is a pure political decision, and you only had to change the fuel, or it is such an enormous cost or time issue which makes it uncompetitive with other solutions.
Besides I really can't understand, why this few GW needs to be subsituted so immediately with coal, it is about 5% of Germany's need so not so systemrelevant. -
Besides I really can't understand, why this few GW needs to be subsituted so immediately with coal, it is about 5% of Germany's need so not so systemrelevant.
Power systems are like that. If you have more consumption than production, the whole grid collapses, so you can't just cut 5%, or even 0.5% of production, you need to replace it with something else; or make customers somehow cut down their consumption. Germany has a lot of heavy industry which can't be turned off. 5% sounds like a small number but it's the difference between life and death (for the industries). -
But Germany is not an island, there are much bigger fluctuations with the neighbours because of the renewables. Compared to that, it is almost peanuts. And coal, especially with older power plants will not help either with that.
So I would think a short period with higher duty cycle on gas power plants until having more import from France, and than building power to gas would be a way more enviromentfriendly solution.
But of course if really not much extra cost or time involved reloading the nuclear plants would be the best but I am still not sure about the technical feasibility, see my questions above. -
But I mean with the needed maintenance for the few years extra running time. Because for me it is not clear wheter this is a pure political decision, and you only had to change the fuel, or it is such an enormous cost or time issue which makes it uncompetitive with other solutions.
That's really a question for the utilities whether they would be happy to run the plants for another year, and if they could market the energy such that they would see a chance of a return on necessary investments. I don't know, I'm not their bean counter.
And the permission to generate electricity ends for the three remaining plants on April 15 as per the German Atomic Energy Act. This was decided by parliament, which is pretty much the definition of a political decision.Besides I really can't understand, why this few GW needs to be subsituted so immediately with coal, it is about 5% of Germany's need so not so systemrelevant.
Again, a political decision to weigh the continuation of NPP operation against the potential risk of a shortage in energy supply, and not something I can say much about. The margins weren't too generous during winter, hopefully next year will be better. Besides that, this statement is certainly true:Power systems are like that. If you have more consumption than production, the whole grid collapses, so you can't just cut 5%, or even 0.5% of production, you need to replace it with something else; or make customers somehow cut down their consumption. Germany has a lot of heavy industry which can't be turned off. 5% sounds like a small number but it's the difference between life and death (for the industries).
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These plants are designed to operate safely for much more than half a century. It's not that extending the operational life by "a few years" is any problem. It's extension after extension after extension after extension which gradually becomes a problem. AFAIK, this practice is being critiqued in the USA.
but if checks, maintenance, etc. have been planned to the deadline and personnel already moved on I suspect it is not a quick or small task to do -
And how much outage would mean the refuelling? If the aim is to make it work for another 1-2 years? Would the costs, risk or time to do it enormus?
Refueling for 1-2 years would not make much sense. Usually the fuel is in the reactor for some 3-4 years with exchanging something like 1/3 every 12-18 months or so. So if they would order new fuel it would be more like for 3-4 years at least - ideally longer to have a mix of old and new rods as the reactors are planed to work with. They may keep a little of the old fuel, but likely not much as the really run it to the end with not much juice left. The unusual fuel mix may need extra certification.
And what if that decision had been made immediately after the government got the results of the studies regarding the possible enlenghtening of the usage of the plants?
If there would be a political will, could it be made economically feasible in a timeframe and for costs that would beat power to gas initiatives (or maybe renewables)during the same time period?
The other point is that the reactors are over-due for a major revision / inspection. They are currently running on extensions/exceptions from the normal rules. So not just the normal short outage to change the fuel, but more like 6 months or langer to check and replace parts that wear-out and upgrade to current standards where needed. A point here is that the replacement parts are no longer planed for and possibly even the machines / molds to make them may no longer be availabe, as they did not plan to ever do this revision anymore. Chances are the mechanics origianlly trained for this job also have a new job. With short notice the revision would likely take longer than normal. So the time (1-2 years) to order an manufacture new fuel may not even be the limiting factor. With the extra effort if would likely not make much sense to restart for only 1 fuel load.
The unlikely scenario to extend the plant life would be some 1-3 years to get them ready for a restart and than maybe 6-10 years, or what ever is left of the planed 40 years of design life. A much shorter time may not be worth the effort.
I don't see a political will for such a longer term commitment and all the regulatory effort for only 3 reactors.