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Germany shutting down last nuclear power plants on April 15th

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rf-messkopf:

--- Quote from: Someone on April 11, 2023, 11:09:27 am ---[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).

--- End quote ---

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.  :)


--- Quote from: Someone on April 11, 2023, 11:09:27 am ---Someone asks about energy, so subtly direct the discussion to power....

--- End quote ---

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).


--- Quote from: Someone on April 11, 2023, 11:09:27 am ---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.

--- End quote ---

True, and I don't think I've disputed that.

Neutrion:

--- Quote from: rf-messkopf on April 10, 2023, 09:50:22 pm ---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.



--- End quote ---

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.

HighVoltage:

--- Quote from: rf-messkopf on April 10, 2023, 09:50:22 pm ---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.


--- End quote ---

 :-+
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.

shapirus:

--- Quote from: HighVoltage on April 11, 2023, 02:02:49 pm ---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.

--- End quote ---
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.

rf-messkopf:

--- Quote from: Neutrion on April 11, 2023, 01:51:41 pm ---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?

--- End quote ---

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.

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