4 ms·

A nuclear power plant doesn't have 100% availability for an arbitrary length of time either.

Moldoteck 2y ago
but usually availability for npp can be planned (maintenance/refueling) unlike say wind/solar output (not referring to day/night but hourly variations)
- RandomLensman 2y ago
  Yes, but still not arbitrary length of time: weather can matter for cooling, there could be strike action, policy action, ...
  - Moldoteck 2y ago
    for weather - that's not a problem for newer designs that account for that. Even in France just a few nr of plants are affected and their output reduced
    - RandomLensman 2y ago
      Doesn't change that arbitrary length of availability isn't a thing.
- bryanlarsen 2y ago
  Wind/solar output is surprisingly predictable 3 days out, and the modern grid can react to changes within seconds.
Octoth0rpe 2y ago
I'm as skeptical of nuclear as a person can get, but I think availability is significantly mitigated by the SMR concept IIUC. Yes, uptime is worse than people might think (nuclear plants are offline a LOT https://www.eia.gov/nuclear/outages/ https://www.eia.gov/nuclear/outages/), but if you've got literally dozens of SMRs chained up, then hypothetically you can expect/handle some % being down at any one time.
- RandomLensman 2y ago
  Let's see how it works out when/if these things are actually running at scale.
mpweiher 2y ago
Nobody claims 100% availability. Doesn't change that nuclear is by far the most reliable electricity generator. The US nuclear fleet has had capacity factors in the 95% range for ages now. And the 5% tend to be planned maintenance/fueling. Not only are the times of unavailablilty very rare and usually plannable, they are also uncorrelated. Seasons, day/night cycles and even large scale weather patterns are highly correlated.
- Retric 2y ago
  Depends on the timeframe. Nuclear is among the least dependable generation sources from a long term capacity standpoint, with multiple incidents taking generation off for long periods. 3 mile island wasn’t a big deal from a health and safety standpoint, but at 4 AM TMI-2 went offline with zero warning and never came back. Similarly you can’t trust timelines for when exactly new generation will come online. Less severe incidents don’t necessarily make the news, but losing 1.3 GW at some random period for weeks or months isn’t particularly uncommon. Sure major incidents are “rare,” but there’s not actually that many nuclear power plants ever constructed.
  - mpweiher 2y ago
    Completely incorrect. Nuclear has the highest reliability of all generation sources, with for example the largest fleet of reactors, the US fleet, consistently coming in at around 95% capacity factor. Most of the remaining 5% is scheduled outages for maintenance and refueling. And both the rare scheduled as well as the even rarer unscheduled outages tend to be uncorrelated. Well, unless radiophobia grips a country and they decide to shut everything down. Trust renewbros to always use a single example to bolster their claims.
    - Retric 2y ago
      Examples are plentiful, read up on why Foreign material exclusion (FME) is such a major concern. Months of completely unplanned outage, 10’s millions in damage and even more in lost production all from a minor mistake. Short term capacity factor is not the same as reliability, the grid needs power every day not some average over a year. Add some turbines and a given dams capacity factor drops but it becomes more valuable due to the added flexibility and redundancies. Lifetime capacity factors of US reactors are a long way from 95% often in the low 80% or below that’s not because the grid doesn’t want their power but because nuclear is unreliable over the long term. 96.04% in 2017, lifetime 78.07% (unreliable). https://en.wikipedia.org/wiki/Browns_Ferry_Nuclear_Plant https://en.wikipedia.org/wiki/Browns_Ferry_Nuclear_Plant 95.7% in 2017 vs 80.25% lifetime (unreliable). https://en.wikipedia.org/wiki/Beaver_Valley_Nuclear_Power_Station https://en.wikipedia.org/wiki/Beaver_Valley_Nuclear_Power_St... And before you think 2017 just had unusually high demand, nope 79.36% capacity factor in 2017. https://en.wikipedia.org/wiki/Arkansas_Nuclear_One https://en.wikipedia.org/wiki/Arkansas_Nuclear_One That’s just another unpleasant reality when trying to actually use nuclear as a major energy source.
EasyMark 2y ago
Once it’s built and operational? It can run near 100% for literally decades at 99.9% plus uptime, no solar source is going to do that because of physics where you can easily vary from 0% to 99% over a single day and have to smooth that out for the grid. Obviously you will need an extra reactor or 3 for when you have to take one of the others offline for maintenance.

but usually availability for npp can be planned (maintenance/refueling) unlike say wind/solar output (not referring to day/night but hourly variations)

RandomLensman 2y ago
Yes, but still not arbitrary length of time: weather can matter for cooling, there could be strike action, policy action, ...
- Moldoteck 2y ago
  for weather - that's not a problem for newer designs that account for that. Even in France just a few nr of plants are affected and their output reduced
  - RandomLensman 2y ago
    Doesn't change that arbitrary length of availability isn't a thing.
bryanlarsen 2y ago
Wind/solar output is surprisingly predictable 3 days out, and the modern grid can react to changes within seconds.

Octoth0rpe 2y ago

I'm as skeptical of nuclear as a person can get, but I think availability is significantly mitigated by the SMR concept IIUC. Yes, uptime is worse than people might think (nuclear plants are offline a LOT https://www.eia.gov/nuclear/outages/ https://www.eia.gov/nuclear/outages/), but if you've got literally dozens of SMRs chained up, then hypothetically you can expect/handle some % being down at any one time.

RandomLensman 2y ago
Let's see how it works out when/if these things are actually running at scale.

mpweiher 2y ago

Nobody claims 100% availability. Doesn't change that nuclear is by far the most reliable electricity generator. The US nuclear fleet has had capacity factors in the 95% range for ages now. And the 5% tend to be planned maintenance/fueling. Not only are the times of unavailablilty very rare and usually plannable, they are also uncorrelated. Seasons, day/night cycles and even large scale weather patterns are highly correlated.

Retric 2y ago
Depends on the timeframe. Nuclear is among the least dependable generation sources from a long term capacity standpoint, with multiple incidents taking generation off for long periods. 3 mile island wasn’t a big deal from a health and safety standpoint, but at 4 AM TMI-2 went offline with zero warning and never came back. Similarly you can’t trust timelines for when exactly new generation will come online. Less severe incidents don’t necessarily make the news, but losing 1.3 GW at some random period for weeks or months isn’t particularly uncommon. Sure major incidents are “rare,” but there’s not actually that many nuclear power plants ever constructed.
- mpweiher 2y ago
  Completely incorrect. Nuclear has the highest reliability of all generation sources, with for example the largest fleet of reactors, the US fleet, consistently coming in at around 95% capacity factor. Most of the remaining 5% is scheduled outages for maintenance and refueling. And both the rare scheduled as well as the even rarer unscheduled outages tend to be uncorrelated. Well, unless radiophobia grips a country and they decide to shut everything down. Trust renewbros to always use a single example to bolster their claims.
  - Retric 2y ago
    Examples are plentiful, read up on why Foreign material exclusion (FME) is such a major concern. Months of completely unplanned outage, 10’s millions in damage and even more in lost production all from a minor mistake. Short term capacity factor is not the same as reliability, the grid needs power every day not some average over a year. Add some turbines and a given dams capacity factor drops but it becomes more valuable due to the added flexibility and redundancies. Lifetime capacity factors of US reactors are a long way from 95% often in the low 80% or below that’s not because the grid doesn’t want their power but because nuclear is unreliable over the long term. 96.04% in 2017, lifetime 78.07% (unreliable). https://en.wikipedia.org/wiki/Browns_Ferry_Nuclear_Plant https://en.wikipedia.org/wiki/Browns_Ferry_Nuclear_Plant 95.7% in 2017 vs 80.25% lifetime (unreliable). https://en.wikipedia.org/wiki/Beaver_Valley_Nuclear_Power_Station https://en.wikipedia.org/wiki/Beaver_Valley_Nuclear_Power_St... And before you think 2017 just had unusually high demand, nope 79.36% capacity factor in 2017. https://en.wikipedia.org/wiki/Arkansas_Nuclear_One https://en.wikipedia.org/wiki/Arkansas_Nuclear_One That’s just another unpleasant reality when trying to actually use nuclear as a major energy source.

EasyMark 2y ago

Once it’s built and operational? It can run near 100% for literally decades at 99.9% plus uptime, no solar source is going to do that because of physics where you can easily vary from 0% to 99% over a single day and have to smooth that out for the grid. Obviously you will need an extra reactor or 3 for when you have to take one of the others offline for maintenance.