3 ms·

> Where has this shown to be realistic at scale? From a pro-nuke guy: no, it has not been shown. The vast majority of the nuclear fuel is low enriched Uranium,

> Where has this shown to be realistic at scale? From a pro-nuke guy: no, it has not been shown. The vast majority of the nuclear fuel is low enriched Uranium, meaning U-238 makes 95% of it or more. A little is transmuted to Plutonium during operation, but more than 90% of the spent fuel is still U-238. We don't currently have the capability to burn that. We may have it one day, but that day is many decades in the future. What nuclear recycling does is to extract unburned U-235 and plutonium from spent fuel. That can only be done once, after that the plutonium is too rich in Pu-240, and only the Pu-239 isotope is optimal for fission. So, those who say we can keep recycling spent fuel, either don't know the whole story, or choose not to tell it. But many companies are working on developing fast reactors. These reactors can burn U-238. In principle they can burn it all. In reality, I think in the short term they'll burn just some part of it. For example, current nuclear plants can generate about 40 to 60 GW-day per ton of fuel. Various new plant proposals can go to 180 GWd/ton [1]; this is impressive, but it's not the factor of 20 you'd expect from fully burning all the uranium in the nuclear fuel. In the link I provided you'll see two reactor types with higher burnups; they are both envisioned to burn thorium. Fingers crossed, but thorium is much more unproven than uranium. In any case, even when burning spent fuel will be possible, it will initially be economically non-profitable. And it will be so for decades. But not for centuries. That's important. Naysayers will try to convince you that spent fuel will be a problem for ten thousand years. But that is only assuming that we freeze all progress to where we are today. Why such an assumption? If you were to place a bet where you miraculously wake up in the future 200 years from now, would you wager that we won't be able to burn the 20'th and 21'st century spent nuclear fuel, or that we will be able to? [1] https://aris.iaea.org/sites/burnup.html https://aris.iaea.org/sites/burnup.html

dotancohen 3y ago
Why isn't the spent nuclear fuel used to conductively pre-heat the water going to the turbine? Then less energy would be required to convert it to steam, making the whole plant more efficient.
- SoftTalker 3y ago
  The steam water is a closed loop. It's boiled, passes through the turbine, condensed back to water, and boiled again. It's already "hot" and doesn't need pre-heating.
  - dotancohen 3y ago
    I see, thanks.
SoftTalker 3y ago
I also think that fast reactors are the answer, and we just have to get over the "proliferation" worry. I mean with all the sanctions the world has imposed we have been unable to prevent Iran, North Korea, other countries from conducting entrichment operations and building weapons. The cat is out of the bag.
- credit_guy 3y ago
  No, proliferation is no joke. And the cat most certainly is not out of the bag. If you split the nuclear era in the first 3 decades and the next 5, then by 1975 seven nations got the bomb: the US, the USSR, the UK, France, China, Israel and India. After that, only three nations did (South Africa, Pakistan and North Korea) and one gave them up eventually. Iran figured out that they can play their cards better if the do not acquire the bomb, but only enrich enough uranium to be able to do that. Many other nations are only "a screwdriver's turn away" from building a bomb, Japan first among them. So much so that there is the concept of "Japan option", or nuclear latency [1]. These countries have looked into the pros and cons of possessing nuclear weapons and decided that it's better for them not to build the bomb, but be able to do that at a moment's notice. In particular, if China were to invade Taiwan, you can be sure than both Japan and South Korea would have the bomb in less than one year, and this is something that the Chinese planners are well aware of. If Japan and South Korea already had the bomb, then it would be much less of a deterrent for China to invade Taiwan. [1]https://en.wikipedia.org/wiki/Nuclear_latency https://en.wikipedia.org/wiki/Nuclear_latency
- Ekaros 3y ago
  We need to start thinking of proliferation as good and desirable thing. Just imagine if instead of long wars in Iraq and Afganistan they had nuclear weapons and delivered retaliatory strike to USA when they were invaded.
jauntywundrkind 3y ago
I'm still so sad that John Kerry had the Integral Fast Reactor funding killed. On-site electro-processing avoided all the scary things about reprocessing being enrichment (and often being off-site). Very fail-safe design. We'd already done prototyping with Experimental Breeder Reactor II. Huge loss to not have the government doing this pioneering. They more than anyone have to be leading the charge; the commercial space is aligned to such a more limited perspective. https://en.wikipedia.org/wiki/Integral_fast_reactor https://en.wikipedia.org/wiki/Integral_fast_reactor A variety of derivative designs have kicked around & a bunch seemed like they were going to get built. Recently GE Hitachi & one of their derived PRISM designs & TerraPower travelling wave folks agreed to try something in Wyoming, but there've been so many similar such plans that've fallen through that I'm not holding my breath.

dotancohen 3y ago

Why isn't the spent nuclear fuel used to conductively pre-heat the water going to the turbine? Then less energy would be required to convert it to steam, making the whole plant more efficient.

SoftTalker 3y ago
The steam water is a closed loop. It's boiled, passes through the turbine, condensed back to water, and boiled again. It's already "hot" and doesn't need pre-heating.
- dotancohen 3y ago
  I see, thanks.

SoftTalker 3y ago

I also think that fast reactors are the answer, and we just have to get over the "proliferation" worry. I mean with all the sanctions the world has imposed we have been unable to prevent Iran, North Korea, other countries from conducting entrichment operations and building weapons. The cat is out of the bag.

credit_guy 3y ago
No, proliferation is no joke. And the cat most certainly is not out of the bag. If you split the nuclear era in the first 3 decades and the next 5, then by 1975 seven nations got the bomb: the US, the USSR, the UK, France, China, Israel and India. After that, only three nations did (South Africa, Pakistan and North Korea) and one gave them up eventually. Iran figured out that they can play their cards better if the do not acquire the bomb, but only enrich enough uranium to be able to do that. Many other nations are only "a screwdriver's turn away" from building a bomb, Japan first among them. So much so that there is the concept of "Japan option", or nuclear latency [1]. These countries have looked into the pros and cons of possessing nuclear weapons and decided that it's better for them not to build the bomb, but be able to do that at a moment's notice. In particular, if China were to invade Taiwan, you can be sure than both Japan and South Korea would have the bomb in less than one year, and this is something that the Chinese planners are well aware of. If Japan and South Korea already had the bomb, then it would be much less of a deterrent for China to invade Taiwan. [1]https://en.wikipedia.org/wiki/Nuclear_latency https://en.wikipedia.org/wiki/Nuclear_latency
Ekaros 3y ago
We need to start thinking of proliferation as good and desirable thing. Just imagine if instead of long wars in Iraq and Afganistan they had nuclear weapons and delivered retaliatory strike to USA when they were invaded.

jauntywundrkind 3y ago

I'm still so sad that John Kerry had the Integral Fast Reactor funding killed. On-site electro-processing avoided all the scary things about reprocessing being enrichment (and often being off-site). Very fail-safe design. We'd already done prototyping with Experimental Breeder Reactor II. Huge loss to not have the government doing this pioneering. They more than anyone have to be leading the charge; the commercial space is aligned to such a more limited perspective. https://en.wikipedia.org/wiki/Integral_fast_reactor https://en.wikipedia.org/wiki/Integral_fast_reactor A variety of derivative designs have kicked around & a bunch seemed like they were going to get built. Recently GE Hitachi & one of their derived PRISM designs & TerraPower travelling wave folks agreed to try something in Wyoming, but there've been so many similar such plans that've fallen through that I'm not holding my breath.