3 ms·

> To the best of my understanding, one of the main reason that MSRs have not gone to market is that the salts are so corrosive that containment over the long te

by hajile 6y ago

> To the best of my understanding, one of the main reason that MSRs have not gone to market is that the salts are so corrosive that containment over the long term is not currently possible. I've wondered why "long-term" is such a huge criteria. One of the biggest nuclear issues today is using them way past their lifespan because they are so expensive to build. Let's assume molten-salt is cheaper to build and less dangerous (from a radioactivity point of view). Why not make expendable designs? Make them smaller so the building requirements are easier. Make them easy to remove and replace. Ease up on the restrictions a bit so they can be replaced every 5-10 years instead of decades. Long-term mass production has tons of advantages. Costs per unit decrease. Defects per unit decrease (this is part of cost per unit usually, but not if a defect gets through inspection). Recycling used units should radically decrease material costs when getting close to peak reactor count (chain of custody paperwork from mine to installation in the nuclear plant is why an otherwise $0.15 screw winds up costing $50-100). Constant employment will build experience over many years and further decrease errors. Once the site design is finalized and enforced, the reactor design can be gradually improved and given the short lifespan, efficiency will increase a minimum of every decade. Likewise, design mistakes (once caught) will only be around a decade at most instead of a half-century like we see today.

deleted 6y ago
[deleted]
escape_goat 6y ago
Kibitzing outside of any expertise that I have, here, but thorium reactors are generally regarded as a significant nuclear weapons proliferation risk. This has been an inhibiting factor with regards to investment in research. This design — cheap and transportable in a standard shipping container — significantly ups the ante on that risk, to put it mildly. Deployed singly, small, low-power, short-lifespan reactors would increase the burden of maintaining regulatory control over those reactors — destined, by design, for catastrophic failure unless they are retired within a safety period — which in turn would the risk of a nuclear contamination incident. This could be mitigated by operating the reactors in banks at a containment/maintenance site. I'm not sure what parts of the reactor could be usefully recycled. All the metals would be embrittled by neutron bombardment.
- davidgrenier 6y ago
  I'm just recalling from the Sorensen's LFTR's videos here, but I had the impression it was the exact opposite in terms of weapon-grade nuclear material.
  - mnw21cam 6y ago
    Anything you take out of a Thorium-fueled reactor is going to contain Uranium-232 and its decay products, which emit easily-detectable and dangerous to nearby living things gamma radiation. U-232 is much harder to separate out from the useful U-233 (which is the fissile fuel that Thorium is converted into) than Uranium 235 is from Uranium 238, so it is very hard to extract clean safe fissile material from a Thorium reactor. This means that a Thorium reactor is really hard to get material from for a nuclear explosion. Any material you do extract is going to be screaming "I'm over here" to any nearby gamma ray detector, and will be dangerous to handle. But if you just wanted to make a dirty bomb by blowing up a small Thorium nuclear plant with conventional explosives, spreading highly radioactive material all over the place, that sounds much more feasible.
- octoberfranklin 6y ago
  > Kibitzing outside of any expertise that I have, here, but thorium reactors are generally regarded as a significant nuclear weapons proliferation risk. Also outside my expertise, but everything I read said the opposite. Wikipedia (which gets true/false questions wrong half the time) says (emphasis added): Uranium-232 (232 U) is an isotope of uranium. It has a half-life of around 68.9 years and is a side product in the thorium cycle. It has been cited as an obstacle to nuclear proliferation using 233U as the fissile material, because the intense gamma radiation emitted by 208Tl (a daughter of 232U, produced relatively quickly) makes the 233U contaminated with it more difficult to handle. https://en.m.wikipedia.org/wiki/Uranium-232 https://en.m.wikipedia.org/wiki/Uranium-232 PS, HN, Y U NO blockquote?!?!
  - lambdatronics 6y ago
    >PS, HN, Y U NO IKR?
redis_mlc 6y ago
> One of the biggest nuclear issues today is using them way past their lifespan because they are so expensive to build. Or they're trying to avoid the staggering and bankrupting cost of decommissioning them.
baybal2 6y ago
A recommended video to watch explaining corrosion protection: https://youtu.be/jO37sMRqv8o https://youtu.be/jO37sMRqv8o
- senectus1 6y ago
  hard not to cringe at the safety standards in that video...
icedistilled 6y ago
>so they can be replaced every 5-10 years Recycling of highly radioactive materials, aka the entire reactor vessel every 5 years, is cost prohibitive. That short of a lifespan will create massive amounts of waste to deal with.
- hajile 6y ago
  Most of the by-products decay away much more rapidly in thorium reactors and the rest are super easy to detect. This should have recycling easier (let it set for a few years after powering down then recycle it necessary). If each unit fit into a slightly oversized shipping container, safely transporting it doesn't seem more difficult than transporting in nuclear material in the first place. Plus, since waste is going right back into a new containment, it probably doesn't have to be as clean provided you can keep workers safe.
  - icedistilled 6y ago
    Actually I did a Ph.d. related to chemical separations of nuclear materials. Granted my direct research was narrow on some aspects of solvent extraction related to actinide separation, but I did get a general impression of other areas from hearing stories and presentations at conferences and such. My impression is that you're vastly underestimating the complexities and challenges of those steps. Yes, this is just an appeal authority type argument, but your point is a lot of generalized high level statements without supporting evidence. What you're saying could be true, but from my impression it's more likely to be magical thinking. I'd love it to be true, but just because we want something to be true or it sounds nice doesn't make it more likely. In fact, we should double our due diligence for claims that tell us what we want to hear.
    - achalhp 6y ago
      I agree. But, in a molten-salt reactor, the vessel and heat exchangers are equivalent to fuel assemblies. Dispose the vessel and heat exchangers similar to Zr-clad million dollar fuel assemblies.(PWR/BWR reload costs $60-100 million per 12-18 months.) Material wise Zr clad is way more expensive than stainless 3XX & graphite combined. Even if Ni-alloy is used in disposable MSRs Ni-alloy+graphite will be slightly cheaper. (Base metal costs: Zr metal: ~$22,700/ton Ni metal: ~$13,100/ton) Many actinides have volatile fluorides. Fluoride volatility is a proven process used to enrich uranium for LWRs. Fuel salt can be disposed after recovering U & Pu. Vacuum distillation is physical separation, which can also be used to further recover expensive base salt FLi7Be. No vacuum distillation is necessary if inexpensive salt is used.
lambdatronics 6y ago
My guess would be this: the cost of a reactor dominates the cost of electricity for fission, so making a reactor last longer reduces the time-averaged cost. Typically, reactors are expected to pay for themselves within 10-20 years. So, a reactor that self-destructs in 5 years needs to cost 2-4x less. It's not clear that MSRs have that kind of up-front cost advantage.

by hajile 6y ago

deleted 6y ago

[deleted]

escape_goat 6y ago

Kibitzing outside of any expertise that I have, here, but thorium reactors are generally regarded as a significant nuclear weapons proliferation risk. This has been an inhibiting factor with regards to investment in research. This design — cheap and transportable in a standard shipping container — significantly ups the ante on that risk, to put it mildly. Deployed singly, small, low-power, short-lifespan reactors would increase the burden of maintaining regulatory control over those reactors — destined, by design, for catastrophic failure unless they are retired within a safety period — which in turn would the risk of a nuclear contamination incident. This could be mitigated by operating the reactors in banks at a containment/maintenance site. I'm not sure what parts of the reactor could be usefully recycled. All the metals would be embrittled by neutron bombardment.

davidgrenier 6y ago
I'm just recalling from the Sorensen's LFTR's videos here, but I had the impression it was the exact opposite in terms of weapon-grade nuclear material.
- mnw21cam 6y ago
  Anything you take out of a Thorium-fueled reactor is going to contain Uranium-232 and its decay products, which emit easily-detectable and dangerous to nearby living things gamma radiation. U-232 is much harder to separate out from the useful U-233 (which is the fissile fuel that Thorium is converted into) than Uranium 235 is from Uranium 238, so it is very hard to extract clean safe fissile material from a Thorium reactor. This means that a Thorium reactor is really hard to get material from for a nuclear explosion. Any material you do extract is going to be screaming "I'm over here" to any nearby gamma ray detector, and will be dangerous to handle. But if you just wanted to make a dirty bomb by blowing up a small Thorium nuclear plant with conventional explosives, spreading highly radioactive material all over the place, that sounds much more feasible.
octoberfranklin 6y ago
> Kibitzing outside of any expertise that I have, here, but thorium reactors are generally regarded as a significant nuclear weapons proliferation risk. Also outside my expertise, but everything I read said the opposite. Wikipedia (which gets true/false questions wrong half the time) says (emphasis added): Uranium-232 (232 U) is an isotope of uranium. It has a half-life of around 68.9 years and is a side product in the thorium cycle. It has been cited as an obstacle to nuclear proliferation using 233U as the fissile material, because the intense gamma radiation emitted by 208Tl (a daughter of 232U, produced relatively quickly) makes the 233U contaminated with it more difficult to handle. https://en.m.wikipedia.org/wiki/Uranium-232 https://en.m.wikipedia.org/wiki/Uranium-232 PS, HN, Y U NO blockquote?!?!
- lambdatronics 6y ago
  >PS, HN, Y U NO IKR?

redis_mlc 6y ago

> One of the biggest nuclear issues today is using them way past their lifespan because they are so expensive to build. Or they're trying to avoid the staggering and bankrupting cost of decommissioning them.

baybal2 6y ago

A recommended video to watch explaining corrosion protection: https://youtu.be/jO37sMRqv8o https://youtu.be/jO37sMRqv8o

senectus1 6y ago
hard not to cringe at the safety standards in that video...

icedistilled 6y ago

>so they can be replaced every 5-10 years Recycling of highly radioactive materials, aka the entire reactor vessel every 5 years, is cost prohibitive. That short of a lifespan will create massive amounts of waste to deal with.

hajile 6y ago
Most of the by-products decay away much more rapidly in thorium reactors and the rest are super easy to detect. This should have recycling easier (let it set for a few years after powering down then recycle it necessary). If each unit fit into a slightly oversized shipping container, safely transporting it doesn't seem more difficult than transporting in nuclear material in the first place. Plus, since waste is going right back into a new containment, it probably doesn't have to be as clean provided you can keep workers safe.
- icedistilled 6y ago
  Actually I did a Ph.d. related to chemical separations of nuclear materials. Granted my direct research was narrow on some aspects of solvent extraction related to actinide separation, but I did get a general impression of other areas from hearing stories and presentations at conferences and such. My impression is that you're vastly underestimating the complexities and challenges of those steps. Yes, this is just an appeal authority type argument, but your point is a lot of generalized high level statements without supporting evidence. What you're saying could be true, but from my impression it's more likely to be magical thinking. I'd love it to be true, but just because we want something to be true or it sounds nice doesn't make it more likely. In fact, we should double our due diligence for claims that tell us what we want to hear.
  - achalhp 6y ago
    I agree. But, in a molten-salt reactor, the vessel and heat exchangers are equivalent to fuel assemblies. Dispose the vessel and heat exchangers similar to Zr-clad million dollar fuel assemblies.(PWR/BWR reload costs $60-100 million per 12-18 months.) Material wise Zr clad is way more expensive than stainless 3XX & graphite combined. Even if Ni-alloy is used in disposable MSRs Ni-alloy+graphite will be slightly cheaper. (Base metal costs: Zr metal: ~$22,700/ton Ni metal: ~$13,100/ton) Many actinides have volatile fluorides. Fluoride volatility is a proven process used to enrich uranium for LWRs. Fuel salt can be disposed after recovering U & Pu. Vacuum distillation is physical separation, which can also be used to further recover expensive base salt FLi7Be. No vacuum distillation is necessary if inexpensive salt is used.

lambdatronics 6y ago

My guess would be this: the cost of a reactor dominates the cost of electricity for fission, so making a reactor last longer reduces the time-averaged cost. Typically, reactors are expected to pay for themselves within 10-20 years. So, a reactor that self-destructs in 5 years needs to cost 2-4x less. It's not clear that MSRs have that kind of up-front cost advantage.