General > General Technical Chat
Germany shutting down last nuclear power plants on April 15th
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daqq:

--- Quote from: asmi on April 10, 2023, 08:33:00 pm ---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.

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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.
rf-messkopf:
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.



--- Quote from: nightfire on April 10, 2023, 07:59:57 pm ---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.

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"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.


--- Quote from: Kleinstein on April 10, 2023, 06:29:13 pm ---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.

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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.


--- Quote from: Kleinstein on April 10, 2023, 06:29:13 pm ---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.

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The provision of balancing power and other grid system services is paid well.


--- Quote from: Kleinstein on April 10, 2023, 06:29:13 pm ---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.

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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).


--- Quote from: Kleinstein on April 10, 2023, 06:29:13 pm ---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.

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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.
Someone:

--- Quote from: rf-messkopf on April 10, 2023, 09:50:22 pm ---
--- Quote from: Kleinstein on April 10, 2023, 06:29:13 pm ---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.
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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.
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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).
james_s:
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?
Someone:

--- Quote from: james_s on April 11, 2023, 01:14:00 am ---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?
--- End quote ---
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
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