I still like my idea for a dynamic fountain core for a molten salt reactor. Simply described, when you hold a garden hose or pump outlet aimed upward below the surface of a body of water, it can form a big hemisphere of rapidly flowing fluid above the water’s surface.
So you take your typical bathroom sink and hook a big high volume pump up to the drain, but with the outflow aimed upwards. This will cause a big mound of water to overflow the sides of the sink (which leads to the heat exchanger, fluid return, and back to the pump). But if you add the volume of the dynamically unstable overflowing mound to the volume of fluid in the sink, you hit critical mass and generate enormous heat.
If the pump shuts off, the volume in the core drops in half immediately and then the rest goes out via a small drain hole at the bottom of the sink. If there’s an excursion that overheats the core the vapors will blast the dynamic bubble of fluid apart, as would an earthquake or other upsets.
The reaction can only continue as long as you’re running the pump because the critical mass is dynamically unstable and wanting to flow back to the drain tank.
It would add another level of safety, and that’s important because we as yet have no evidence that Martians are particularly competent at running anything.
I don’t know, if you listen to Ken, there’s nothing they can’t do.
Are these martians human? Then they can do anything humans can do. Can a subset of humans do everything all humans can do? No, but that has never stopped a subset from doing what they can.
>> dynamic fountain core for a molten salt reactor
Interesting idea. I see three concerns:
The shape of the hemisphere is a dynamic balance of several forces, including gravity. It will work differently on Mars.
I think you will need a neutron moderator/reflector internal to the salt flow or around it. Maybe both.
The outflow of hot salt is along the entire circumference of the salt sphere. That maximizes the size of the engineering problem for the most difficult material issue.
Not quite as failsafe but simpler is the drain plug; you’ve got the same sink with a heat exchanger and a drain plug of a material carefully chosen to have a melting point just a bit above safe operating temperature for the reactor.
Off-topic: George, you might be interested in my latest addiction: http://childrenofadeadearth.com, a *very* hard sci-fi space combat simulator.
That is awesome.
Thats how the molten-salt reactor at Oak Ridge worked….and it worked well. Just a big cleanup if it ever melted.
“Journalism is about covering important stories. With a pillow, until they stop moving.”
h/t @Iowahawk
NASA will treat this new idea like modern journalism. Wouldn’t want to rock the boat & risk their funding.
By the way, anybody on here try GAB.AI yet?
I’m registered in gab.ai, but it’s too much like twitter for my tastes.
I’m on there, and it’s a little wild. Just sayin’.
All molten salt reactors are problematic. The least bad fast reactors are probably lead-bismuth reactors. The Soviets used them to power the Alfa-class nuclear submarines. The Russians are currently building a large demo power plant based on this technology (BREST-300).
I’m not terribly fond of molten sodium or fluoride… Any time I read about something that burns in contact with water it makes me kind of nervous. Having to use UF6 in the cycle is already bad enough as it is but at least it’s limited to uranium separation facilities.
There are plenty of viable space nuclear reactor designs but this one seems particularly, well, complicated. The neutron source alone is going to add needless weight and volume to a space system. It’s something you would want to rather use on the ground.
The CERMET and Pebble Bed reactor designs seem more viable to me. The technology could probably be shared with the US Navy. AFAIK you could easily use a space nuclear power reactor on a submarine.
The bulk of “fuel” for a LFTR is a fluoride salt that won’t burn in water. It might dissolve in water if it was cool enough to not boil the water away. It is very much not sodium or sodium-potassium that will react aggressively with water. Or any other variety of liquid metal cooled reactor.
Lead-bismuth becomes loaded with polonium under neutron bombardment. Lead-magnesium would be safer.
The reactor core is sexy to talk about, but I suspect the biggest challenge to adapting earth-based designs is cooling.
Looking purely at the thermodynamics for a minute, it’s the temperature difference between the reactor core and your external coolant you’re harnessing. Here on earth we got plenty of liquid water; in space and maybe on Mars you’ll have to use giant radiators instead, and you may need to run them a lot hotter than liquid water to keep size and mass down…
Dynamic radiators would be the lightest weight for a space reactor. Start with a LFTR using a Super Critical CO2 turbine drive for the superconducting electrical generators. Powdered metal, of a higher melting point than whatever will shut down the LFTR, that is conveyed (by screws, blown gas, or other means) to and through the heat exchanger for cooling the CO2 working fluid of the turbine. The powder would be strongly negatively charged, and the tossed out into space from one place on the spaceship that is negatively charged to another place on it that is positively charged. The metal powder, with an enormous surface area, will radiate heat away at a huge rate, and would collect at the positively charged point to be transferred back to the heat exchanger.
If Mars atmosphere is too thin to allow cooling by convection, then we should investigate a continual cycle of compressing cold atmospheric CO2, to replace hotter CO2 from the bottom of the Super Critical CO2 turbine’s heat cycle. This could actually give us slightly higher efficiency, IIRC.
Ditto the pebble bed design. The Chinese have a working model that they’ve intentionally crashed into safe shutdown. Excess heat stops the reaction. The only consideration with that one is feeding and discharging the balls in a weightless environment
I still like my idea for a dynamic fountain core for a molten salt reactor. Simply described, when you hold a garden hose or pump outlet aimed upward below the surface of a body of water, it can form a big hemisphere of rapidly flowing fluid above the water’s surface.
So you take your typical bathroom sink and hook a big high volume pump up to the drain, but with the outflow aimed upwards. This will cause a big mound of water to overflow the sides of the sink (which leads to the heat exchanger, fluid return, and back to the pump). But if you add the volume of the dynamically unstable overflowing mound to the volume of fluid in the sink, you hit critical mass and generate enormous heat.
If the pump shuts off, the volume in the core drops in half immediately and then the rest goes out via a small drain hole at the bottom of the sink. If there’s an excursion that overheats the core the vapors will blast the dynamic bubble of fluid apart, as would an earthquake or other upsets.
The reaction can only continue as long as you’re running the pump because the critical mass is dynamically unstable and wanting to flow back to the drain tank.
It would add another level of safety, and that’s important because we as yet have no evidence that Martians are particularly competent at running anything.
I don’t know, if you listen to Ken, there’s nothing they can’t do.
Are these martians human? Then they can do anything humans can do. Can a subset of humans do everything all humans can do? No, but that has never stopped a subset from doing what they can.
>> dynamic fountain core for a molten salt reactor
Interesting idea. I see three concerns:
The shape of the hemisphere is a dynamic balance of several forces, including gravity. It will work differently on Mars.
I think you will need a neutron moderator/reflector internal to the salt flow or around it. Maybe both.
The outflow of hot salt is along the entire circumference of the salt sphere. That maximizes the size of the engineering problem for the most difficult material issue.
Not quite as failsafe but simpler is the drain plug; you’ve got the same sink with a heat exchanger and a drain plug of a material carefully chosen to have a melting point just a bit above safe operating temperature for the reactor.
Off-topic: George, you might be interested in my latest addiction: http://childrenofadeadearth.com, a *very* hard sci-fi space combat simulator.
That is awesome.
Thats how the molten-salt reactor at Oak Ridge worked….and it worked well. Just a big cleanup if it ever melted.
“Journalism is about covering important stories. With a pillow, until they stop moving.”
h/t @Iowahawk
NASA will treat this new idea like modern journalism. Wouldn’t want to rock the boat & risk their funding.
By the way, anybody on here try GAB.AI yet?
I’m registered in gab.ai, but it’s too much like twitter for my tastes.
I’m on there, and it’s a little wild. Just sayin’.
All molten salt reactors are problematic. The least bad fast reactors are probably lead-bismuth reactors. The Soviets used them to power the Alfa-class nuclear submarines. The Russians are currently building a large demo power plant based on this technology (BREST-300).
I’m not terribly fond of molten sodium or fluoride… Any time I read about something that burns in contact with water it makes me kind of nervous. Having to use UF6 in the cycle is already bad enough as it is but at least it’s limited to uranium separation facilities.
There are plenty of viable space nuclear reactor designs but this one seems particularly, well, complicated. The neutron source alone is going to add needless weight and volume to a space system. It’s something you would want to rather use on the ground.
The CERMET and Pebble Bed reactor designs seem more viable to me. The technology could probably be shared with the US Navy. AFAIK you could easily use a space nuclear power reactor on a submarine.
The bulk of “fuel” for a LFTR is a fluoride salt that won’t burn in water. It might dissolve in water if it was cool enough to not boil the water away. It is very much not sodium or sodium-potassium that will react aggressively with water. Or any other variety of liquid metal cooled reactor.
Lead-bismuth becomes loaded with polonium under neutron bombardment. Lead-magnesium would be safer.
The reactor core is sexy to talk about, but I suspect the biggest challenge to adapting earth-based designs is cooling.
Looking purely at the thermodynamics for a minute, it’s the temperature difference between the reactor core and your external coolant you’re harnessing. Here on earth we got plenty of liquid water; in space and maybe on Mars you’ll have to use giant radiators instead, and you may need to run them a lot hotter than liquid water to keep size and mass down…
Dynamic radiators would be the lightest weight for a space reactor. Start with a LFTR using a Super Critical CO2 turbine drive for the superconducting electrical generators. Powdered metal, of a higher melting point than whatever will shut down the LFTR, that is conveyed (by screws, blown gas, or other means) to and through the heat exchanger for cooling the CO2 working fluid of the turbine. The powder would be strongly negatively charged, and the tossed out into space from one place on the spaceship that is negatively charged to another place on it that is positively charged. The metal powder, with an enormous surface area, will radiate heat away at a huge rate, and would collect at the positively charged point to be transferred back to the heat exchanger.
If Mars atmosphere is too thin to allow cooling by convection, then we should investigate a continual cycle of compressing cold atmospheric CO2, to replace hotter CO2 from the bottom of the Super Critical CO2 turbine’s heat cycle. This could actually give us slightly higher efficiency, IIRC.
Ditto the pebble bed design. The Chinese have a working model that they’ve intentionally crashed into safe shutdown. Excess heat stops the reaction. The only consideration with that one is feeding and discharging the balls in a weightless environment