10 ms·

Molten Salt Reactors

155 points by zeristor 7y ago

fnord77 7y ago
> Protactinium-233 decays to pure, weapons-grade U-233
- jlhawn 7y ago
  I thought it was Uranium 235 which was the common weapons material, so I looked up Wikipedia [1]: > ... While it is thus possible to use uranium-233 as the fissile material of a nuclear weapon, speculation[8] aside, there is scant publicly available information on this isotope actually having been weaponized ... [1] https://en.wikipedia.org/wiki/Uranium-233#Weapon_material https://en.wikipedia.org/wiki/Uranium-233#Weapon_material
  - deleted 7y ago
    [deleted]
  - acidburnNSA 7y ago
    In the nuclear industry, U-233 is well known as an excellent weapons material [1]. It's simply a matter of its nuclear properties, which are well known. "The fast critical mass of U-233 is almost identical to that for Pu-239 and the spontaneous fission rate is much lower, reducing to negligible levels the problem of a spontaneous fission neutron prematurely initiating the chain reaction -- even in a “gun-type” design such as used for the U-235 Hiroshima bomb (see Table 1)." [1] U-232 and the Proliferation-Resistance of U-233 in Spent Fuel - http://scienceandglobalsecurity.org/archive/sgs09kang.pdf http://scienceandglobalsecurity.org/archive/sgs09kang.pdf
  - JshWright 7y ago
    They're both good options, U-235 is "simpler" to make though.
  - baobrien 7y ago
    U-235 is the only naturally occurring fissile isotope of uranium. In raw uranium out of the ground, it makes up about 0.7%, the rest being U-238. U-233 is also fissile, but only really made in thorium breeder reactors.
- DennisP 7y ago
  That's one reason some of the MSR companies are going with uranium fuel. MSRs don't have to be thorium.
petschge 7y ago
The usual quip in the industry is that the remote maintenance is such a complicated robotics problem. that which ever company is able to solve it, is better off converting to a robotics company and just drive Kuka, Fanuc and ABB out of business.
- ambicapter 7y ago
  Is it a hard robotics problem or a hard radiation-hardening problem?
  - TaylorAlexander 7y ago
    Completely robotically maintaining a complex machine sounds like a hard robotics problem to me. Of course it can be designed for machine manipulation but that seems like a pretty complex fusion of robotics and nuclear reactor design. So I think it would be a lot of work.
    - darkpuma 7y ago
      It seems to me that the simplest reactors tend to be the most dangerous. I'm thinking of the Windscale fire and SL-1 in particular. One of the theories for what went wrong at SL-1 is that it was a murder-suicide, caused by the man tasked with physically manipulating the control rods of the reactor. I think robotic control is better for something like that. Robots are more predictable. One of the aggravating factors at Windscale was their inability to perform maintenance tasks behind the reactor. They had canisters of radioactive material smashing open behind the reactor and it took them ages to even notice. That was a very simple reactor design; basically a nuclear pile. It was also an awful design that was irradiating England even before it caught fire.
      - tim333 7y ago
        The Windscale reactors were built in a hurry in 1950 to produce nuclear weapons after Russia managed to test it's first atom bomb in 1949 and are not really representative of modern power generating technology.
w0mbat 7y ago
Or just use that money for solar panels and batteries and not build a combination power plant / doomsday weapon.
- acidburnNSA 7y ago
  MIT studies suggest that deeply decarbonizing is actually cheaper when you do some nuclear alongside your variable renewables + storage [1]. The cost of filling those seasonal solar gaps and 10-day wind gaps gets pretty large without nukes. [1] https://energy.mit.edu/research/future-nuclear-energy-carbon-constrained-world/ https://energy.mit.edu/research/future-nuclear-energy-carbon...
  - pfdietz 7y ago
    Studies that purport to show that nuclear has a place due to inability of renewables to fill those gaps are usually assuming renewables + short term storage cannot fill those gaps. But renewables + short term storage + hydrogen can, and probably more cheaply than a system with nuclear reactors.
    - AnthonyMouse 7y ago
      What's hydrogen supposed to add? It's just a type of storage, and probably not even the cheapest one.
      - pfdietz 7y ago
        Hydrogen has low capital cost. The capital cost/energy of storing hydrogen underground will be much less than the cost of storing that energy in a battery. If you have a storage scenario where the energy is stored for very long times, there will be few cycles of that system over its economic lifespan, so minimizing capital cost (even if that means much lower round trip efficiency) is very important. One would still use more efficient short term storage (and over-installation of renewables sources) for diurnal load leveling. Hydrogen can also be turned back to electrical power (at lousy efficiency) with cheap hardware. In particular, simple cycle gas turbine power plants with efficiency of 40% cost maybe $400/kW. Compare this to $8-10K/kW for a new nuclear power plant.
achalhp 7y ago
From the article: >if something goes wrong in a MSR and the temperature starts going up, a freeze plug can melt, A MSR does not need any sort of valve to drain the fuel. ORNL-MSBR was designed to drain the core when pumps stopped working. The real advantage of freeze valve is that is uses no moving parts and maintanence free/friendly. ORNL-4528: "The fuel salt pump and its sump, or pump tank, are below the reactor vessel, so that failure of the pump to develop the required head causes the salt to drain from the reactor vessel through the pump tank to the fuel salt drain tank."
achalhp 7y ago
From the article: >Problems with Molten Salt Reactors... >...but similar problems may show up in long-lived power reactors. Author assumes that MSR components should last as long as vessels and secondary heat exchangers of solid-fuel reactors. The author should understand that vessel and primary heat exchanger of a fluid-fuel reactor is anologus to fuel rods. Solid fuel reactors just dispose primary heat exchangers or fuel rods every few years. Example: Zircolloy tubes worth a MSR vessel + heat exchanger is just disposed along with partially fissioned degraded solid fuel every 4.5 years in a LWR. Zircolloy (Hafnium separated nuclear grade zirconium + additives) is more expensive than commercially available nickel based alloys. Graphite is a solid with a crystal structure. Crystal structure degradation under radiation is permanent and there is nothing anyone can do to reverse it. Solar panels degrade similarly. Nuclear industry handles solid-fuel rods which are far more radioactive than MSR graphite and complains that it can't handle MSR graphite. Just shows that either industry is incompetent or it is not interested in efficient fluid-fuel reactors. Does nuclear industry aims >1000 GW of nuclear capacity? Does nuclear industry care to solve global energy related issues? Efficiency really matters when we have >1000 GW of installed nuclear capacity. If all energy is obtained from nuclear, (12000-16000 GW) even seawater uranium get used up in 40-60 years with inefficient solid-fuel reactors.
- philipkglass 7y ago
  > Efficiency really matters when we have >1000 GW of installed nuclear capacity. If all energy is obtained from nuclear, (12000-16000 GW) even seawater uranium get used up in 40-60 years with inefficient solid-fuel reactors. That can't be right. About 200 tonnes of natural uranium is needed to produce 1 GWe per year in conventional reactors [1]. That's 3,200,000 tonnes per year if you mean 16000 GW in the form of electricity, or closer to 1 million tonnes per year if you're referring to primary (thermal) energy. Seawater contains about 4.5 billion tonnes of uranium [2]. That's well over a thousand years' worth of uranium, either way. [1] https://www.world-nuclear.org/information-library/nuclear-fuel-cycle/introduction/nuclear-fuel-cycle-overview.aspx https://www.world-nuclear.org/information-library/nuclear-fu... [2] http://large.stanford.edu/courses/2012/ph241/ferguson2/ http://large.stanford.edu/courses/2012/ph241/ferguson2/
  - 7y ago
AtlasBarfed 7y ago
I thought LIFTR was the coolest thing ever. MSRs could have revolutionized power generation... about two decades ago. Solar/Wind/Storage are beating almost everything. Everything they aren't... they will, very soon. It's possible that MSRs could be scaled down and their liquid nature means that the reactor could simply be replaced on a schedule and the entire old reactor "reprocessed". But the investment won't be there with wind/solar/battery eating everyone's lunch. And that's IF regulatory was simplified and IF you were able to get enough starting fuel to initiate breeding of the thorium.
- ajross 7y ago
  This is exactly the issue. Nuclear simply missed the boat. It couldn't win against coal on a balance sheet and it's surely not going to catch up to renewables now. There's nothing wrong with it. A cheap fission technology would be a good thing. But at this stage literally no one is interesting in throwing money at a technology that is now into its eighth (!) decade of maturity. The low hanging fruit got picked by our grandparents.
  - dgudkov 7y ago
    >It couldn't win against coal on a balance sheet It did win against coal on a balance sheet. It's the environmental concerns that stopped nuclear from proliferation, not the economical.
    - wffurr 7y ago
      And the environmental costs for nuclear were internalized by regulation, while the same did not happen for coal. This is still well within the realm of economics.
      - twic 7y ago
        > the environmental costs for nuclear were internalized by regulation, while the same did not happen for coal It very much did happen for coal. That's what this whole global warming business is about.
sandGorgon 7y ago
The largest reserves of thorium exist in India and China - two of the most energy hungry and polluting economies. One is on the UN Security Council and the other has a unique waiver from the US Congress on proliferation - so fissile material production is not the primary concern. Both India and China have massive deployments of renewable energy, yet the demand for energy is outstripping projected build-out. LTFR is going to be one of the best answers if it can be made safe.
- sien 7y ago
  https://en.wikipedia.org/wiki/Occurrence_of_thorium https://en.wikipedia.org/wiki/Occurrence_of_thorium From there it seems like India, Australia & the US all have large thorium reserves. There is certainly heaps of it.
  - sandGorgon 7y ago
    not disagreeing. however, the hunger for energy in India and China is causing outsize investments in MSR. For example - https://www.nextbigfuture.com/2017/12/china-spending-us3-3-billion-on-molten-salt-nuclear-reactors-for-faster-aircraft-carriers-and-in-flying-drones.html https://www.nextbigfuture.com/2017/12/china-spending-us3-3-b...
achalhp 7y ago
>Complex chemical plant This is not a disadvantage for all MSRs. Only breeders need chemical plant. Not fair to compare a solid-fuel burner to liquid-fuel breeder. Let us compare liquid fuel breeder vs. solid-fuel breeder: Reprocessing solid-fuel involves more complex chemical plant with physical mechanisms to declad and convert solid-fuel to a processable liquid. Fabricate processed liquid to solid-fuel and put it back in the reactor. Solid fuel breeders have additional physical and chemical processes/steps.
jillesvangurp 7y ago
The elephant in the room with any kind of fission reactor is that they are going to need a lot of security. Even when the fuel and waste product is not weapons grade uranium, it's still highly radioactive and a great source of material for a dirty bomb. Basically anything that goes boom combined with small amounts of radioactive material and a bit of wind is a great way to depopulate e.g. large cities. So, having lots of small molten salt reactors all over the planet, which seems like the key selling point, is not a great idea from that point of view. Having them in or near any kind of conflict zone would be super risky. And according to this article there is actually some weapons grade uranium being produced as well which makes this even more problematic. The security aspect would make this a lot more expensive than it already is and cost is already on the high side even before you consider that. This is a problem with traditional reactors as well but they have the advantage that they are huge facilities and that there are only a handful of them; so securing them is relatively easy. People are suggesting this as complementing renewables but the cold hard truth is that renewables are already dirt cheap and on track to continue to drop in price by magnitudes for the next decades. That includes battery storage as well. Already quite cheap, also dropping in price, and typically already factored into e.g. new solar bids that are killing competing bids for coal and gas plants (or in some cases shutting them down prematurely). Even at the current prices, that's a problem for any kind of nuclear solutions being contemplated right now. At the low end of the spectrum, we are talking 2 cents per kwh currently. Imagine this dropping to something like half a cent or even less. At those prices, the security alone would make nuclear too expensive probably. A 1 mw facility would have basically be generating only about 500-2000$ worth of energy per hour but only at peak demand. There's no guarantee prices won't drop way below that either. Any kind of operational overhead would be a problem. Needing 24x7 intense security would be very undesirable.
- acidburnNSA 7y ago
  Are you suggesting that variable renewables plus batteries will approach prices that are... too cheap to meter? Looking at current cost VRE trends, when variable sources contribute up to 4% of world energy, and surrounded by massive amounts of cheap but high-carbon natural gas, and assuming that the trends will just continue exponentially downward without serious complication, is optimistic. Cost of integration of variable sources plus batteries is expected in many studies and somewhat intuitively to skyrocket as market penetration increases. When you have enough VRE to cover 100% including the big evening peak with batteries during a clear summer day, the extra generation you build to fill the other gaps gets curtailed. But you have to fill daily and then seasonal gaps, worldwide, including heat in winter and worldwide transportation (not just electricity). Buying that battery that is only even needed at all every third day is 3x the price, yet we prefer if the power doesn't brownout with this frequency. This is difficult. Already we're seeing NIBMYism in large solar installations in california and with transmissions lines. That gets worse with scale. Nuclear today is a hedge against the possibility that deeply carbonizing with variable renewables + storage at world scale will be harder than we all think and hope it will be. That said, nuclear certainly needs to drop capital and O&M cost dramatically if it wants to play the game. And security is indeed a big factor in this. Its competition in the small-footprint dispatchable world is natural gas with full CCS, which is also looking pretty cheap.
achalhp 7y ago
>Tritium production: If lithium is used in the salt, tritium will be produced, Not a disadvantage for all MSRs. Both lithium and beryllium can be avoided. FLiBe is required for efficient MSRs and MSBR. >Mobile fission products It is the only disadvantage common to all molten-salt reactors and all fluid-fuel reactors. Pumps and pipes have to handle a hot radioactive liquid. > Material Degradation Common to all nuclear reactors, solar, coal boiler tubes, etc. Components used in reactor core do not last long. MSRs dispose nickel tubes and LWRs dispose zirconium tubes and uranium. >Proliferation...The problem with MSRs, then, is that the fuel is already completely cut open and melted. >it will be difficult for the IAEA to distinguish plate-out losses from actual proliferative losses. The fuel salt loop can be sealed tamper-proof. The entire fuel salt loop is analogous to a fuel assembly. Weigh the entire fuel salt loop. Vapor pressure of actinide-halide salt is very low at operating temperatures. Actinides don't move out of this loop.
- DennisP 7y ago
  Regarding pumps and pipes, the Moltex design avoids them entirely. Liquid fuel is contained in vertical fuel rods, open at the top to allow escape of gaseous fission products (some of which are strong neutron absorbers). The pipes are mostly immersed in a pool of molten salt coolant. https://www.moltexenergy.com/ https://www.moltexenergy.com/
pweezy 7y ago
> Molten salt fuels were first conceived of in the late 1940s, when people began thinking of nuclear powered airplanes! > The idea was to have very long range bombers in the air at all times I had never heard of this idea, and thought it was super interesting. Imagine aircraft that could stay in the air indefinitely (for some practical purposes), carrying massive loads without fuel being a concern. Similar to nuclear aircraft carriers and submarines, at least conceptually. https://en.m.wikipedia.org/wiki/Nuclear-powered_aircraft https://en.m.wikipedia.org/wiki/Nuclear-powered_aircraft
- Symmetry 7y ago
  In the long run nuclear jets could be really useful for the exploration of planets that don't have free oxygen in the atmosphere like Venus, Saturn, etc.
rkachowski 7y ago
There's a lot of references to "plate out" in the article and most of the results I find on Google are paywalled by Elsevier - can some explain what the term means or point me to a resource?
- philipkglass 7y ago
  When fuel nuclei split apart in a nuclear reactor, their split fragments form a variety of lighter elements. Some of these elements are so-called "noble" metals -- metals that tend toward remaining chemically stable as metals, rather than as chemical compounds with other elements. Silver, ruthenium, and palladium are some examples of noble metals. More typical metallic elements like potassium and iron, by contrast, tend to be found on Earth as oxidized chemical compounds rather than as metals. In a molten salt reactor, most fission products either stay dissolved in the salt mix or are lost from the mix as stable gases. The noble metals are different. Their tendency is to reform as solid metal. They tend to accumulate as a metallic layer or plate of metal over other solid surfaces they come into contact with. That's what is meant by plating out. Here is a document that specifically addresses noble metal plate-out in molten salt reactors: http://www.skyscrubber.com/Molten-Salt-Reactor%20Technology%20Gaps.pdf http://www.skyscrubber.com/Molten-Salt-Reactor%20Technology%... See section III.C.
nimish 7y ago
The big problem with nuclear driven steam turbines is that they cannot be cheaper than thermal coal driven steam turbines due to costs-- construction, operation and decommissioning. Their LCOE is just not great and not lowering quick enough. Even thermal coal is getting out priced by solar/wind+ batteries. And the latter will always get cheaper due to economies of scale and learning rate reductions not to mention core technological advances. Nuclear would have kept us out of the carbon free energy mess decades ago but it's not the answer in 2019.

155 points by zeristor 7y ago

fnord77 7y ago

> Protactinium-233 decays to pure, weapons-grade U-233

jlhawn 7y ago
I thought it was Uranium 235 which was the common weapons material, so I looked up Wikipedia [1]: > ... While it is thus possible to use uranium-233 as the fissile material of a nuclear weapon, speculation[8] aside, there is scant publicly available information on this isotope actually having been weaponized ... [1] https://en.wikipedia.org/wiki/Uranium-233#Weapon_material https://en.wikipedia.org/wiki/Uranium-233#Weapon_material
- deleted 7y ago
  [deleted]
- acidburnNSA 7y ago
  In the nuclear industry, U-233 is well known as an excellent weapons material [1]. It's simply a matter of its nuclear properties, which are well known. "The fast critical mass of U-233 is almost identical to that for Pu-239 and the spontaneous fission rate is much lower, reducing to negligible levels the problem of a spontaneous fission neutron prematurely initiating the chain reaction -- even in a “gun-type” design such as used for the U-235 Hiroshima bomb (see Table 1)." [1] U-232 and the Proliferation-Resistance of U-233 in Spent Fuel - http://scienceandglobalsecurity.org/archive/sgs09kang.pdf http://scienceandglobalsecurity.org/archive/sgs09kang.pdf
- JshWright 7y ago
  They're both good options, U-235 is "simpler" to make though.
- baobrien 7y ago
  U-235 is the only naturally occurring fissile isotope of uranium. In raw uranium out of the ground, it makes up about 0.7%, the rest being U-238. U-233 is also fissile, but only really made in thorium breeder reactors.
DennisP 7y ago
That's one reason some of the MSR companies are going with uranium fuel. MSRs don't have to be thorium.

petschge 7y ago

The usual quip in the industry is that the remote maintenance is such a complicated robotics problem. that which ever company is able to solve it, is better off converting to a robotics company and just drive Kuka, Fanuc and ABB out of business.

ambicapter 7y ago
Is it a hard robotics problem or a hard radiation-hardening problem?
- TaylorAlexander 7y ago
  Completely robotically maintaining a complex machine sounds like a hard robotics problem to me. Of course it can be designed for machine manipulation but that seems like a pretty complex fusion of robotics and nuclear reactor design. So I think it would be a lot of work.
  - darkpuma 7y ago
    It seems to me that the simplest reactors tend to be the most dangerous. I'm thinking of the Windscale fire and SL-1 in particular. One of the theories for what went wrong at SL-1 is that it was a murder-suicide, caused by the man tasked with physically manipulating the control rods of the reactor. I think robotic control is better for something like that. Robots are more predictable. One of the aggravating factors at Windscale was their inability to perform maintenance tasks behind the reactor. They had canisters of radioactive material smashing open behind the reactor and it took them ages to even notice. That was a very simple reactor design; basically a nuclear pile. It was also an awful design that was irradiating England even before it caught fire.
    - tim333 7y ago
      The Windscale reactors were built in a hurry in 1950 to produce nuclear weapons after Russia managed to test it's first atom bomb in 1949 and are not really representative of modern power generating technology.

w0mbat 7y ago

Or just use that money for solar panels and batteries and not build a combination power plant / doomsday weapon.

acidburnNSA 7y ago
MIT studies suggest that deeply decarbonizing is actually cheaper when you do some nuclear alongside your variable renewables + storage [1]. The cost of filling those seasonal solar gaps and 10-day wind gaps gets pretty large without nukes. [1] https://energy.mit.edu/research/future-nuclear-energy-carbon-constrained-world/ https://energy.mit.edu/research/future-nuclear-energy-carbon...
- pfdietz 7y ago
  Studies that purport to show that nuclear has a place due to inability of renewables to fill those gaps are usually assuming renewables + short term storage cannot fill those gaps. But renewables + short term storage + hydrogen can, and probably more cheaply than a system with nuclear reactors.
  - AnthonyMouse 7y ago
    What's hydrogen supposed to add? It's just a type of storage, and probably not even the cheapest one.
    - pfdietz 7y ago
      Hydrogen has low capital cost. The capital cost/energy of storing hydrogen underground will be much less than the cost of storing that energy in a battery. If you have a storage scenario where the energy is stored for very long times, there will be few cycles of that system over its economic lifespan, so minimizing capital cost (even if that means much lower round trip efficiency) is very important. One would still use more efficient short term storage (and over-installation of renewables sources) for diurnal load leveling. Hydrogen can also be turned back to electrical power (at lousy efficiency) with cheap hardware. In particular, simple cycle gas turbine power plants with efficiency of 40% cost maybe $400/kW. Compare this to $8-10K/kW for a new nuclear power plant.

achalhp 7y ago

From the article: >if something goes wrong in a MSR and the temperature starts going up, a freeze plug can melt, A MSR does not need any sort of valve to drain the fuel. ORNL-MSBR was designed to drain the core when pumps stopped working. The real advantage of freeze valve is that is uses no moving parts and maintanence free/friendly. ORNL-4528: "The fuel salt pump and its sump, or pump tank, are below the reactor vessel, so that failure of the pump to develop the required head causes the salt to drain from the reactor vessel through the pump tank to the fuel salt drain tank."

achalhp 7y ago

From the article: >Problems with Molten Salt Reactors... >...but similar problems may show up in long-lived power reactors. Author assumes that MSR components should last as long as vessels and secondary heat exchangers of solid-fuel reactors. The author should understand that vessel and primary heat exchanger of a fluid-fuel reactor is anologus to fuel rods. Solid fuel reactors just dispose primary heat exchangers or fuel rods every few years. Example: Zircolloy tubes worth a MSR vessel + heat exchanger is just disposed along with partially fissioned degraded solid fuel every 4.5 years in a LWR. Zircolloy (Hafnium separated nuclear grade zirconium + additives) is more expensive than commercially available nickel based alloys. Graphite is a solid with a crystal structure. Crystal structure degradation under radiation is permanent and there is nothing anyone can do to reverse it. Solar panels degrade similarly. Nuclear industry handles solid-fuel rods which are far more radioactive than MSR graphite and complains that it can't handle MSR graphite. Just shows that either industry is incompetent or it is not interested in efficient fluid-fuel reactors. Does nuclear industry aims >1000 GW of nuclear capacity? Does nuclear industry care to solve global energy related issues? Efficiency really matters when we have >1000 GW of installed nuclear capacity. If all energy is obtained from nuclear, (12000-16000 GW) even seawater uranium get used up in 40-60 years with inefficient solid-fuel reactors.

philipkglass 7y ago
> Efficiency really matters when we have >1000 GW of installed nuclear capacity. If all energy is obtained from nuclear, (12000-16000 GW) even seawater uranium get used up in 40-60 years with inefficient solid-fuel reactors. That can't be right. About 200 tonnes of natural uranium is needed to produce 1 GWe per year in conventional reactors [1]. That's 3,200,000 tonnes per year if you mean 16000 GW in the form of electricity, or closer to 1 million tonnes per year if you're referring to primary (thermal) energy. Seawater contains about 4.5 billion tonnes of uranium [2]. That's well over a thousand years' worth of uranium, either way. [1] https://www.world-nuclear.org/information-library/nuclear-fuel-cycle/introduction/nuclear-fuel-cycle-overview.aspx https://www.world-nuclear.org/information-library/nuclear-fu... [2] http://large.stanford.edu/courses/2012/ph241/ferguson2/ http://large.stanford.edu/courses/2012/ph241/ferguson2/
- 7y ago

AtlasBarfed 7y ago

I thought LIFTR was the coolest thing ever. MSRs could have revolutionized power generation... about two decades ago. Solar/Wind/Storage are beating almost everything. Everything they aren't... they will, very soon. It's possible that MSRs could be scaled down and their liquid nature means that the reactor could simply be replaced on a schedule and the entire old reactor "reprocessed". But the investment won't be there with wind/solar/battery eating everyone's lunch. And that's IF regulatory was simplified and IF you were able to get enough starting fuel to initiate breeding of the thorium.

ajross 7y ago
This is exactly the issue. Nuclear simply missed the boat. It couldn't win against coal on a balance sheet and it's surely not going to catch up to renewables now. There's nothing wrong with it. A cheap fission technology would be a good thing. But at this stage literally no one is interesting in throwing money at a technology that is now into its eighth (!) decade of maturity. The low hanging fruit got picked by our grandparents.
- dgudkov 7y ago
  >It couldn't win against coal on a balance sheet It did win against coal on a balance sheet. It's the environmental concerns that stopped nuclear from proliferation, not the economical.
  - wffurr 7y ago
    And the environmental costs for nuclear were internalized by regulation, while the same did not happen for coal. This is still well within the realm of economics.
    - twic 7y ago
      > the environmental costs for nuclear were internalized by regulation, while the same did not happen for coal It very much did happen for coal. That's what this whole global warming business is about.

sandGorgon 7y ago

The largest reserves of thorium exist in India and China - two of the most energy hungry and polluting economies. One is on the UN Security Council and the other has a unique waiver from the US Congress on proliferation - so fissile material production is not the primary concern. Both India and China have massive deployments of renewable energy, yet the demand for energy is outstripping projected build-out. LTFR is going to be one of the best answers if it can be made safe.

sien 7y ago
https://en.wikipedia.org/wiki/Occurrence_of_thorium https://en.wikipedia.org/wiki/Occurrence_of_thorium From there it seems like India, Australia & the US all have large thorium reserves. There is certainly heaps of it.
- sandGorgon 7y ago
  not disagreeing. however, the hunger for energy in India and China is causing outsize investments in MSR. For example - https://www.nextbigfuture.com/2017/12/china-spending-us3-3-billion-on-molten-salt-nuclear-reactors-for-faster-aircraft-carriers-and-in-flying-drones.html https://www.nextbigfuture.com/2017/12/china-spending-us3-3-b...

achalhp 7y ago

>Complex chemical plant This is not a disadvantage for all MSRs. Only breeders need chemical plant. Not fair to compare a solid-fuel burner to liquid-fuel breeder. Let us compare liquid fuel breeder vs. solid-fuel breeder: Reprocessing solid-fuel involves more complex chemical plant with physical mechanisms to declad and convert solid-fuel to a processable liquid. Fabricate processed liquid to solid-fuel and put it back in the reactor. Solid fuel breeders have additional physical and chemical processes/steps.

jillesvangurp 7y ago

The elephant in the room with any kind of fission reactor is that they are going to need a lot of security. Even when the fuel and waste product is not weapons grade uranium, it's still highly radioactive and a great source of material for a dirty bomb. Basically anything that goes boom combined with small amounts of radioactive material and a bit of wind is a great way to depopulate e.g. large cities. So, having lots of small molten salt reactors all over the planet, which seems like the key selling point, is not a great idea from that point of view. Having them in or near any kind of conflict zone would be super risky. And according to this article there is actually some weapons grade uranium being produced as well which makes this even more problematic. The security aspect would make this a lot more expensive than it already is and cost is already on the high side even before you consider that. This is a problem with traditional reactors as well but they have the advantage that they are huge facilities and that there are only a handful of them; so securing them is relatively easy. People are suggesting this as complementing renewables but the cold hard truth is that renewables are already dirt cheap and on track to continue to drop in price by magnitudes for the next decades. That includes battery storage as well. Already quite cheap, also dropping in price, and typically already factored into e.g. new solar bids that are killing competing bids for coal and gas plants (or in some cases shutting them down prematurely). Even at the current prices, that's a problem for any kind of nuclear solutions being contemplated right now. At the low end of the spectrum, we are talking 2 cents per kwh currently. Imagine this dropping to something like half a cent or even less. At those prices, the security alone would make nuclear too expensive probably. A 1 mw facility would have basically be generating only about 500-2000$ worth of energy per hour but only at peak demand. There's no guarantee prices won't drop way below that either. Any kind of operational overhead would be a problem. Needing 24x7 intense security would be very undesirable.

acidburnNSA 7y ago
Are you suggesting that variable renewables plus batteries will approach prices that are... too cheap to meter? Looking at current cost VRE trends, when variable sources contribute up to 4% of world energy, and surrounded by massive amounts of cheap but high-carbon natural gas, and assuming that the trends will just continue exponentially downward without serious complication, is optimistic. Cost of integration of variable sources plus batteries is expected in many studies and somewhat intuitively to skyrocket as market penetration increases. When you have enough VRE to cover 100% including the big evening peak with batteries during a clear summer day, the extra generation you build to fill the other gaps gets curtailed. But you have to fill daily and then seasonal gaps, worldwide, including heat in winter and worldwide transportation (not just electricity). Buying that battery that is only even needed at all every third day is 3x the price, yet we prefer if the power doesn't brownout with this frequency. This is difficult. Already we're seeing NIBMYism in large solar installations in california and with transmissions lines. That gets worse with scale. Nuclear today is a hedge against the possibility that deeply carbonizing with variable renewables + storage at world scale will be harder than we all think and hope it will be. That said, nuclear certainly needs to drop capital and O&M cost dramatically if it wants to play the game. And security is indeed a big factor in this. Its competition in the small-footprint dispatchable world is natural gas with full CCS, which is also looking pretty cheap.

achalhp 7y ago

>Tritium production: If lithium is used in the salt, tritium will be produced, Not a disadvantage for all MSRs. Both lithium and beryllium can be avoided. FLiBe is required for efficient MSRs and MSBR. >Mobile fission products It is the only disadvantage common to all molten-salt reactors and all fluid-fuel reactors. Pumps and pipes have to handle a hot radioactive liquid. > Material Degradation Common to all nuclear reactors, solar, coal boiler tubes, etc. Components used in reactor core do not last long. MSRs dispose nickel tubes and LWRs dispose zirconium tubes and uranium. >Proliferation...The problem with MSRs, then, is that the fuel is already completely cut open and melted. >it will be difficult for the IAEA to distinguish plate-out losses from actual proliferative losses. The fuel salt loop can be sealed tamper-proof. The entire fuel salt loop is analogous to a fuel assembly. Weigh the entire fuel salt loop. Vapor pressure of actinide-halide salt is very low at operating temperatures. Actinides don't move out of this loop.

DennisP 7y ago
Regarding pumps and pipes, the Moltex design avoids them entirely. Liquid fuel is contained in vertical fuel rods, open at the top to allow escape of gaseous fission products (some of which are strong neutron absorbers). The pipes are mostly immersed in a pool of molten salt coolant. https://www.moltexenergy.com/ https://www.moltexenergy.com/

pweezy 7y ago

> Molten salt fuels were first conceived of in the late 1940s, when people began thinking of nuclear powered airplanes! > The idea was to have very long range bombers in the air at all times I had never heard of this idea, and thought it was super interesting. Imagine aircraft that could stay in the air indefinitely (for some practical purposes), carrying massive loads without fuel being a concern. Similar to nuclear aircraft carriers and submarines, at least conceptually. https://en.m.wikipedia.org/wiki/Nuclear-powered_aircraft https://en.m.wikipedia.org/wiki/Nuclear-powered_aircraft

Symmetry 7y ago
In the long run nuclear jets could be really useful for the exploration of planets that don't have free oxygen in the atmosphere like Venus, Saturn, etc.

rkachowski 7y ago

There's a lot of references to "plate out" in the article and most of the results I find on Google are paywalled by Elsevier - can some explain what the term means or point me to a resource?

philipkglass 7y ago
When fuel nuclei split apart in a nuclear reactor, their split fragments form a variety of lighter elements. Some of these elements are so-called "noble" metals -- metals that tend toward remaining chemically stable as metals, rather than as chemical compounds with other elements. Silver, ruthenium, and palladium are some examples of noble metals. More typical metallic elements like potassium and iron, by contrast, tend to be found on Earth as oxidized chemical compounds rather than as metals. In a molten salt reactor, most fission products either stay dissolved in the salt mix or are lost from the mix as stable gases. The noble metals are different. Their tendency is to reform as solid metal. They tend to accumulate as a metallic layer or plate of metal over other solid surfaces they come into contact with. That's what is meant by plating out. Here is a document that specifically addresses noble metal plate-out in molten salt reactors: http://www.skyscrubber.com/Molten-Salt-Reactor%20Technology%20Gaps.pdf http://www.skyscrubber.com/Molten-Salt-Reactor%20Technology%... See section III.C.

nimish 7y ago

The big problem with nuclear driven steam turbines is that they cannot be cheaper than thermal coal driven steam turbines due to costs-- construction, operation and decommissioning. Their LCOE is just not great and not lowering quick enough. Even thermal coal is getting out priced by solar/wind+ batteries. And the latter will always get cheaper due to economies of scale and learning rate reductions not to mention core technological advances. Nuclear would have kept us out of the carbon free energy mess decades ago but it's not the answer in 2019.