OT: IEEE spectrum on grid parity in China

[Jeroen Belleman]

On 2019-08-24 20:45, Rick C wrote:

On Saturday, August 24, 2019 at 2:23:55 PM UTC-4, Jeroen Belleman
wrote:
On 2019-08-24 09:26, Rick C wrote:
On Saturday, August 24, 2019 at 1:55:14 AM UTC-4,
upsid...@downunder.com wrote:

This is just the situation in France with high nuclear
penetration. During weekends when consumption is lower, some
nuclears are throttled back or even stopped for the weekends.

Temperature variation will cause stress to tubing, so you rally
try to avoid rapid power level changes.


[...] They also don't address the cost issue. Are electricity
costs high in France?


0.123 Euros/kWh for the day rate and 0.087 Euro/kWh for the night
rate.

I wonder how the new EPR reactor will impact that? More than triple
the estimated cost and quadrupled schedule. Do you think they will
continue to sell these reactors?

I'm willing to bet they don't load follow with these.

I still haven't found how nukes avoid Xe135 poisoning when load
following. Maybe it's a very, very slow load following. Xe135 has a
half life of some 6 or so hours as does the precursor I135. That
means when you throttle back the Xe killing neutrons fall back, but
the production of more Xe135 doesn't for hours allowing Xe135 to
increase and absorb more neutrons than is desirable. Cut back too
quickly and you can't bring the reactor back up for hours until the
Xe135 decays.

Maybe they have a way of maintaining neutron production even as the
energy output is reduced? I have no idea how they would accomplish
that. Or maybe the load following is just very shallow. I thought I
read about at least one reactor that could be cut far back, maybe to
30% without poisoning.

Power is regulated by raising or lowering the control rods,
and by manipulating the concentration of boric acid in the
primary circuit water. The problem is that raising the control
rods exposes a region of the core that is relatively less
poisoned by Xe135, and which therefore risks being overly
reactive. This is controlled by positioning fractional-height
control rods.

I haven't yet found much about the typical range of the output
power regulation. I guess it isn't a lot. Typical time constants
are a few minutes.

Jeroen Belleman

 

[Lasse Langwadt Christense]

søndag den 25. august 2019 kl. 00.10.16 UTC+2 skrev Rick C:

On Saturday, August 24, 2019 at 5:53:46 PM UTC-4, Jeroen Belleman wrote:
On 2019-08-24 20:45, Rick C wrote:
On Saturday, August 24, 2019 at 2:23:55 PM UTC-4, Jeroen Belleman
wrote:
On 2019-08-24 09:26, Rick C wrote:
On Saturday, August 24, 2019 at 1:55:14 AM UTC-4,
upsid...@downunder.com wrote:

This is just the situation in France with high nuclear
penetration. During weekends when consumption is lower, some
nuclears are throttled back or even stopped for the weekends.

Temperature variation will cause stress to tubing, so you rally
try to avoid rapid power level changes.


[...] They also don't address the cost issue. Are electricity
costs high in France?


0.123 Euros/kWh for the day rate and 0.087 Euro/kWh for the night
rate.

I wonder how the new EPR reactor will impact that? More than triple
the estimated cost and quadrupled schedule. Do you think they will
continue to sell these reactors?

I'm willing to bet they don't load follow with these.

I still haven't found how nukes avoid Xe135 poisoning when load
following. Maybe it's a very, very slow load following. Xe135 has a
half life of some 6 or so hours as does the precursor I135. That
means when you throttle back the Xe killing neutrons fall back, but
the production of more Xe135 doesn't for hours allowing Xe135 to
increase and absorb more neutrons than is desirable. Cut back too
quickly and you can't bring the reactor back up for hours until the
Xe135 decays.

Maybe they have a way of maintaining neutron production even as the
energy output is reduced? I have no idea how they would accomplish
that. Or maybe the load following is just very shallow. I thought I
read about at least one reactor that could be cut far back, maybe to
30% without poisoning.


Power is regulated by raising or lowering the control rods,
and by manipulating the concentration of boric acid in the
primary circuit water. The problem is that raising the control
rods exposes a region of the core that is relatively less
poisoned by Xe135, and which therefore risks being overly
reactive. This is controlled by positioning fractional-height
control rods.

I haven't yet found much about the typical range of the output
power regulation. I guess it isn't a lot. Typical time constants
are a few minutes.

Yes, they have to worry about hot spots, but the Xe135 poisoning is an issue 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 slowly, 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 amounts 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.

https://www.oecd-nea.org/ndd/reports/2011/load-following-npp.pdf

 

[Rick C]

On Sunday, August 25, 2019 at 5:04:54 AM UTC-4, Lasse Langwadt Christensen wrote:

søndag den 25. august 2019 kl. 00.10.16 UTC+2 skrev Rick C:
On Saturday, August 24, 2019 at 5:53:46 PM UTC-4, Jeroen Belleman wrote:
On 2019-08-24 20:45, Rick C wrote:
On Saturday, August 24, 2019 at 2:23:55 PM UTC-4, Jeroen Belleman
wrote:
On 2019-08-24 09:26, Rick C wrote:
On Saturday, August 24, 2019 at 1:55:14 AM UTC-4,
upsid...@downunder.com wrote:

This is just the situation in France with high nuclear
penetration. During weekends when consumption is lower, some
nuclears are throttled back or even stopped for the weekends.

Temperature variation will cause stress to tubing, so you rally
try to avoid rapid power level changes.


[...] They also don't address the cost issue. Are electricity
costs high in France?


0.123 Euros/kWh for the day rate and 0.087 Euro/kWh for the night
rate.

I wonder how the new EPR reactor will impact that? More than triple
the estimated cost and quadrupled schedule. Do you think they will
continue to sell these reactors?

I'm willing to bet they don't load follow with these.

I still haven't found how nukes avoid Xe135 poisoning when load
following. Maybe it's a very, very slow load following. Xe135 has a
half life of some 6 or so hours as does the precursor I135. That
means when you throttle back the Xe killing neutrons fall back, but
the production of more Xe135 doesn't for hours allowing Xe135 to
increase and absorb more neutrons than is desirable. Cut back too
quickly and you can't bring the reactor back up for hours until the
Xe135 decays.

Maybe they have a way of maintaining neutron production even as the
energy output is reduced? I have no idea how they would accomplish
that. Or maybe the load following is just very shallow. I thought I
read about at least one reactor that could be cut far back, maybe to
30% without poisoning.


Power is regulated by raising or lowering the control rods,
and by manipulating the concentration of boric acid in the
primary circuit water. The problem is that raising the control
rods exposes a region of the core that is relatively less
poisoned by Xe135, and which therefore risks being overly
reactive. This is controlled by positioning fractional-height
control rods.

I haven't yet found much about the typical range of the output
power regulation. I guess it isn't a lot. Typical time constants
are a few minutes.

Yes, they have to worry about hot spots, but the Xe135 poisoning is an issue 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 slowly, 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 amounts 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.



https://www.oecd-nea.org/ndd/reports/2011/load-following-npp.pdf

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 challenging the operation in the load-following mode with large magnitudes of power 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 adjusted, 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 water 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 seems to be somehow related to "mirror" particles, but they seem to be entirely 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 does..

--

Rick C.

++ Get 1,000 miles of free Supercharging
++ Tesla referral code - https://ts.la/richard11209

 

[Lasse Langwadt Christense]

søndag den 25. august 2019 kl. 18.25.09 UTC+2 skrev Rick C:

On Sunday, August 25, 2019 at 5:04:54 AM UTC-4, Lasse Langwadt Christensen wrote:
søndag den 25. august 2019 kl. 00.10.16 UTC+2 skrev Rick C:
On Saturday, August 24, 2019 at 5:53:46 PM UTC-4, Jeroen Belleman wrote:
On 2019-08-24 20:45, Rick C wrote:
On Saturday, August 24, 2019 at 2:23:55 PM UTC-4, Jeroen Belleman
wrote:
On 2019-08-24 09:26, Rick C wrote:
On Saturday, August 24, 2019 at 1:55:14 AM UTC-4,
upsid...@downunder.com wrote:

This is just the situation in France with high nuclear
penetration. During weekends when consumption is lower, some
nuclears are throttled back or even stopped for the weekends.

Temperature variation will cause stress to tubing, so you rally
try to avoid rapid power level changes.


[...] They also don't address the cost issue. Are electricity
costs high in France?


0.123 Euros/kWh for the day rate and 0.087 Euro/kWh for the night
rate.

I wonder how the new EPR reactor will impact that? More than triple
the estimated cost and quadrupled schedule. Do you think they will
continue to sell these reactors?

I'm willing to bet they don't load follow with these.

I still haven't found how nukes avoid Xe135 poisoning when load
following. Maybe it's a very, very slow load following. Xe135 has a
half life of some 6 or so hours as does the precursor I135. That
means when you throttle back the Xe killing neutrons fall back, but
the production of more Xe135 doesn't for hours allowing Xe135 to
increase and absorb more neutrons than is desirable. Cut back too
quickly and you can't bring the reactor back up for hours until the
Xe135 decays.

Maybe they have a way of maintaining neutron production even as the
energy output is reduced? I have no idea how they would accomplish
that. Or maybe the load following is just very shallow. I thought I
read about at least one reactor that could be cut far back, maybe to
30% without poisoning.


Power is regulated by raising or lowering the control rods,
and by manipulating the concentration of boric acid in the
primary circuit water. The problem is that raising the control
rods exposes a region of the core that is relatively less
poisoned by Xe135, and which therefore risks being overly
reactive. This is controlled by positioning fractional-height
control rods.

I haven't yet found much about the typical range of the output
power regulation. I guess it isn't a lot. Typical time constants
are a few minutes.

Yes, they have to worry about hot spots, but the Xe135 poisoning is an issue 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 slowly, 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 amounts 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.



https://www.oecd-nea.org/ndd/reports/2011/load-following-npp.pdf

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 challenging the operation in the load-following mode with large magnitudes of power 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 adjusted, 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 water 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 seems to be somehow related to "mirror" particles, but they seem to be entirely 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 does.

afaict it is an absorption that doesn't result in fission

http://www.radioactivity.eu.com/site/pages/Slow_Neutrons.htm

 

[Rick C]

On Sunday, August 25, 2019 at 12:53:59 PM UTC-4, Lasse Langwadt Christensen wrote:

søndag den 25. august 2019 kl. 18.25.09 UTC+2 skrev Rick C:
On Sunday, August 25, 2019 at 5:04:54 AM UTC-4, Lasse Langwadt Christensen wrote:

https://www.oecd-nea.org/ndd/reports/2011/load-following-npp.pdf

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 challenging the operation in the load-following mode with large magnitudes of power 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 adjusted, 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 water 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 seems to be somehow related to "mirror" particles, but they seem to be entirely 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 does.


afaict it is an absorption that doesn't result in fission

http://www.radioactivity.eu.com/site/pages/Slow_Neutrons.htm

I suppose that's it, but I'm trying to understand this part.

"Doppler effect(change in fuel temperature)The Doppler effect of reactivity 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 reactivity is decreased. The Doppler effect is an important stabilising effect."

Are they saying 238U can absorb a neutron and *never* result in decay to 238Np? 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 larger than the uranium-238 nuclei which forms the majority but have a much smaller probability of "sterile" capture without fission.'

The fissile isotopes have a large cross section and so absorb the neutron more easily. Why are they talking about the "sterile" capture of uranium-238? I'm not sure what that means really. 238U has a short half life turning into 238Np. What would be "sterile" about it? Are they just using the term to say that 238U undergoes beta decay rather than fission when the neutron is captured? It's not an alternative path?

That makes sense in the original paper. There they are saying a higher temperature 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 neutron 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.

--- Get 1,000 miles of free Supercharging
--- Tesla referral code - https://ts.la/richard11209