3 ms·

> Ramping up and down in response to renewables will be an important function of any nuclear reactor installed today. Realistically, it's not going to happen.

> Ramping up and down in response to renewables will be an important function of any nuclear reactor installed today. Realistically, it's not going to happen. PWRs are inherently stable, that's one of their big selling points. If anything goes wrong and the reactor becomes too hot, the water expands, moderates less the neutrons and they don't slow down enough to trigger fission events, so the rate of fission decreases. If for some reason the reactor stops producing enough heat, the water cools down and more fission starts happening. And there are other negative feedback processes in place too, for example Doppler broadening [1]. This is great for safety, but not so great for load following. If you want to load follow, it's probably going to be many times cheaper to just invest in a bunch of batteries. [1] https://en.wikipedia.org/wiki/Doppler_broadening#Applications_and_caveats https://en.wikipedia.org/wiki/Doppler_broadening#Application...

innrautha 4y ago
That depends on what they mean by load following. While you can load-follow by changing reactor power (like the French do extensively). Westinghouse has long been promoting thermal storage based load following in their other reactor designs [1]. Where instead of perturbing the reactor's power, you divert the thermal output to a molten salt thermal battery when you want to decrease power suddenly, and use the battery to pre-heat feedwater when you want to increase power suddenly. For their LFR design they are claiming they should be able to load follow within 65-125% of nominal full power (ramping at 10%/minute). As long as the load-following averages out to 100% power over a long/short enough time period the reactor never has to change power level. The only really needed to do this at any thermal plant is to over size the steam turbines, install some piping, and build an insulated salt tank. Of course Westinghouse hasn't built any plants with that feature since it doesn't make economic sense without variable energy pricing. [1] "Status Report – Westinghouse Lead Fast Reactor," (Westinghouse Electric Company LLC, United States of America), https://aris.iaea.org/PDF/W-LFR_2020.pdf https://aris.iaea.org/PDF/W-LFR_2020.pdf
- p1mrx 4y ago
  Light water reactors (like the AP300) don't get hot enough for molten salt storage. That requires one of the high temperature Gen IV reactors.
  - innrautha 4y ago
    That just means for LWR applications you need to switch the storage media. Any thermal plant could implement heat storage if they identify a medium with a large latent heat of fusion that is around where you want to preheat your working fluid to. The salt used for energy storage is normally a eutectic mixture of ~60% sodium nitrate and ~40% potassium nitrate (not NaCl) and has a melting temperature of ~260 °C. The secondary on a PWR has a maximum temperature of 275 °C. So within the liquid range of typical thermal storage salts, though I suspect finer tuning of the salt composition would be used to reduce the melting temperature to closer to the feed water temperature of ~220 °C.
    - p1mrx 4y ago
      Heat storage is technically possible at any temperature, but it's much more cost effective at 600°C than 300°C.
pfdietz 4y ago
And if you're going with batteries, you might as well charge them with a source that has low levelized cost. That's not nuclear.

innrautha 4y ago

That depends on what they mean by load following. While you can load-follow by changing reactor power (like the French do extensively). Westinghouse has long been promoting thermal storage based load following in their other reactor designs [1]. Where instead of perturbing the reactor's power, you divert the thermal output to a molten salt thermal battery when you want to decrease power suddenly, and use the battery to pre-heat feedwater when you want to increase power suddenly. For their LFR design they are claiming they should be able to load follow within 65-125% of nominal full power (ramping at 10%/minute). As long as the load-following averages out to 100% power over a long/short enough time period the reactor never has to change power level. The only really needed to do this at any thermal plant is to over size the steam turbines, install some piping, and build an insulated salt tank. Of course Westinghouse hasn't built any plants with that feature since it doesn't make economic sense without variable energy pricing. [1] "Status Report – Westinghouse Lead Fast Reactor," (Westinghouse Electric Company LLC, United States of America), https://aris.iaea.org/PDF/W-LFR_2020.pdf https://aris.iaea.org/PDF/W-LFR_2020.pdf

p1mrx 4y ago
Light water reactors (like the AP300) don't get hot enough for molten salt storage. That requires one of the high temperature Gen IV reactors.
- innrautha 4y ago
  That just means for LWR applications you need to switch the storage media. Any thermal plant could implement heat storage if they identify a medium with a large latent heat of fusion that is around where you want to preheat your working fluid to. The salt used for energy storage is normally a eutectic mixture of ~60% sodium nitrate and ~40% potassium nitrate (not NaCl) and has a melting temperature of ~260 °C. The secondary on a PWR has a maximum temperature of 275 °C. So within the liquid range of typical thermal storage salts, though I suspect finer tuning of the salt composition would be used to reduce the melting temperature to closer to the feed water temperature of ~220 °C.
  - p1mrx 4y ago
    Heat storage is technically possible at any temperature, but it's much more cost effective at 600°C than 300°C.

pfdietz 4y ago

And if you're going with batteries, you might as well charge them with a source that has low levelized cost. That's not nuclear.