Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Molten Salt Reactors

whatisnuclear.com

Post reply on HN
Print view View original

11–20 of 122 posts

Re: Molten Salt Reactors

#11

Post by achalhp »

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."

Re: Molten Salt Reactors

#12

Post by baobrien »

jlhawn wrote: post #3
fnord77 wrote: post #2

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

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

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.

Re: Molten Salt Reactors

#13

Post by ambicapter »

petschge wrote: post #5

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.

Is it a hard robotics problem or a hard radiation-hardening problem?

Re: Molten Salt Reactors

#14

Post by achalhp »

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.

Re: Molten Salt Reactors

#15

Post by philipkglass »

achalhp wrote: post #14

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 o…

> 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-fu...

[2] http://large.stanford.edu/courses/2012/ph241/ferguson2/

Re: Molten Salt Reactors

#16

Post by achalhp »

philipkglass wrote: post #15
achalhp wrote: post #14

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 o…

> 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 ele…

Firstly heat from inefficient low temperature solid-fuel reactors can't be used directly for many applications. So consider electricity. Cars/planes/kitchen-stoves cant use uranium or nuclear heat!!

All 4.5 billion tons can't be extratcted. More we extract, concentration decreases and harder it gets. I keep asking this question: If seawater extraction of metals is practical, why aren't we extracting other costly metals now? https://twitter.com/AchalHP/status/1011661441412337665

Re: Molten Salt Reactors

#17

Post by acidburnNSA »

achalhp wrote: post #16
philipkglass wrote: post #15

Earlier quoted context omitted.

> 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 ele…

Firstly heat from inefficient low temperature solid-fuel reactors can't be used directly for many applications. So consider electricity. Cars/planes/kitchen-stoves cant use uranium or nuclear heat!! All 4.5 billion tons can't be extratcted. More we extract, concentration decreases and harder it gets. I keep asking this question: If seawater extraction of metals is practical, why aren't we extracting other costly meta…

Don't confuse solid fuel with traditional light water reactors. The highest temperature reactors are triso fueled helium cooled solid fuel reactors like HTTR with outlet temperatures over 1000C. Also, fast breeder reactors with solid fuel are just as sustainable as any fluid fuel breeder.

Molten salt is one of about a dozen advanced reactor techs that has huge potential.

Hard part is economics. Hazardous coolant has been a pain to maintain cheaply so far.

Also seawater uranium replenishes from erosion and plate tectonics so it will effectively never decrease in concentration, even if we pull it out at world scale.

http://large.stanford.edu/publications/coal/references/docs/...

Re: Molten Salt Reactors

#18

Post by PopeDotNinja »

achalhp wrote: post #16
philipkglass wrote: post #15

Earlier quoted context omitted.

> 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 ele…

Firstly heat from inefficient low temperature solid-fuel reactors can't be used directly for many applications. So consider electricity. Cars/planes/kitchen-stoves cant use uranium or nuclear heat!! All 4.5 billion tons can't be extratcted. More we extract, concentration decreases and harder it gets. I keep asking this question: If seawater extraction of metals is practical, why aren't we extracting other costly meta…

One could make a pedantic argument that a battery powered anything can use nuclear, but I agree with your point.

Re: Molten Salt Reactors

#19

Post by AtlasBarfed »

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.

Re: Molten Salt Reactors

#20

Post by ajross »

AtlasBarfed wrote: post #19

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 the…

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.

Post reply on HN