Yes, they have to worry about hot spots, but the Xe135 poisoning is an issu e in general not really the same at all. If they want to dial the reactor back to 50% from 100% Xe135 poisoning becomes an issue unless it is done sl owly, over the course of hours or days.
This is what I'm wondering how they get around. Is it because they simply don't exercise that much control over the power output? Instead they only cut the power in small increments? If they need to cut back by larger amou nts do they have to take a long time to do it?
One report I read about reactors in France said they load follow the daily cycle. Many days that is 50% here in the US. That would be hard to do in
24 hours I would expect. I can't find any details on how this is done.
--
Rick C.
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sue in general not really the same at all. If they want to dial the reacto r back to 50% from 100% Xe135 poisoning becomes an issue unless it is done slowly, over the course of hours or days.
y don't exercise that much control over the power output? Instead they onl y cut the power in small increments? If they need to cut back by larger am ounts do they have to take a long time to do it?
y cycle. Many days that is 50% here in the US. That would be hard to do i n 24 hours I would expect. I can't find any details on how this is done.
issue in general not really the same at all. If they want to dial the reac tor back to 50% from 100% Xe135 poisoning becomes an issue unless it is don e slowly, over the course of hours or days.
ply don't exercise that much control over the power output? Instead they o nly cut the power in small increments? If they need to cut back by larger amounts do they have to take a long time to do it?
ily cycle. Many days that is 50% here in the US. That would be hard to do in 24 hours I would expect. I can't find any details on how this is done.
I guess there is no magic that lets reactors load follow. The efforts they take seem to be complex, "The management of these axial oscillations of the reactor power and 135Xe is an additional effect making chall enging the operation in the load-following mode with large magnitudes of po wer variations."
It largely appears that the issue of "poisoning" is more a relative factor and not an absolute issue. That is, if the boron concentration is not adju sted, the control rods alone are not sufficient to bring a poisoned reactor back up to full power. But if the boron concentration in the coolant wate r can be adjusted, the full range of power control can be managed.
Thanks for the link. I couldn't find anything this useful, even if it was a tough read.
Now if you can find something that explains what a "sterile neutron" is. I found this term and as hard as I look, I can't find what it means. It see ms to be somehow related to "mirror" particles, but they seem to be entirel y theoretical still. The paper you linked to refers to "sterile neutron ab sorption by 238U". I'm assuming it has something to do with the neutron no t having the impact on the stability of 238/239U that a normal neutron does .
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Rick C.
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n issue in general not really the same at all. If they want to dial the re actor back to 50% from 100% Xe135 poisoning becomes an issue unless it is d one slowly, over the course of hours or days.
imply don't exercise that much control over the power output? Instead they only cut the power in small increments? If they need to cut back by large r amounts do they have to take a long time to do it?
daily cycle. Many days that is 50% here in the US. That would be hard to do in 24 hours I would expect. I can't find any details on how this is don e.
ey take seem to be complex, "The management of these axial oscillation s of the reactor power and 135Xe is an additional effect making cha llenging the operation in the load-following mode with large magnitudes of power variations."
r and not an absolute issue. That is, if the boron concentration is not ad justed, the control rods alone are not sufficient to bring a poisoned react or back up to full power. But if the boron concentration in the coolant wa ter can be adjusted, the full range of power control can be managed.
s a tough read.
I found this term and as hard as I look, I can't find what it means. It s eems to be somehow related to "mirror" particles, but they seem to be entir ely theoretical still. The paper you linked to refers to "sterile neutron absorption by 238U". I'm assuming it has something to do with the neutron not having the impact on the stability of 238/239U that a normal neutron do es.
afaict it is an absorption that doesn't result in fission
they take seem to be complex, "The management of these axial oscillati ons of the reactor power and 135Xe is an additional effect making c hallenging the operation in the load-following mode with large magnitudes o f power variations."
tor and not an absolute issue. That is, if the boron concentration is not adjusted, the control rods alone are not sufficient to bring a poisoned rea ctor back up to full power. But if the boron concentration in the coolant water can be adjusted, the full range of power control can be managed.
was a tough read.
. I found this term and as hard as I look, I can't find what it means. It seems to be somehow related to "mirror" particles, but they seem to be ent irely theoretical still. The paper you linked to refers to "sterile neutro n absorption by 238U". I'm assuming it has something to do with the neutro n not having the impact on the stability of 238/239U that a normal neutron does.
I suppose that's it, but I'm trying to understand this part.
"Doppler effect(change in fuel temperature)The Doppler effect of reacti vity is mainly related to the resonant absorption of neutrons by
238U. When the temperature of the fuel rises, the resonant absorption is enhanced, including the sterile neutron absorption by 238U. Thus, the re activity is decreased. The Doppler effect is an important stabilising effec t."
Are they saying 238U can absorb a neutron and *never* result in decay to 23
8Np? That doesn't make sense.
This part in your most recent link, 'Everything happens as if slow neutrons see the tiny minority of uranium-235 or plutonium-239 nuclei much more lar ger than the uranium-238 nuclei which forms the majority but have a much sm aller probability of "sterile" capture without fission.'
The fissile isotopes have a large cross section and so absorb the neutron m ore easily. Why are they talking about the "sterile" capture of uranium-23
8? I'm not sure what that means really. 238U has a short half life turnin g into 238Np. What would be "sterile" about it? Are they just using the t erm to say that 238U undergoes beta decay rather than fission when the neut ron is captured? It's not an alternative path?
That makes sense in the original paper. There they are saying a higher tem perature increases the absorption of neutrons by 238U which does not result in fission any time soon ans so lowers reactivity helping to moderate the reaction. I assume beta decay releases much less energy than does fission.
Or maybe the issue that gives it the label "sterile" is the loss of the neu tron from the chain reaction more so than the lower energy released?
I bet that's what the term means. While less energy is released, the real issue is the loss of the neutron which slows the overall reaction. Duh!
--
Rick C.
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