3 ms·

Lemme guess, they haven't become popular yet because there wasn't a way to weaponise the results?

choeger 7y ago
To the contrary. You can use these things to breed very dangerous material for bombs. Hence most industrial countries (say Germany) are nudged by the superpowers to not implement such devices. If Iran would build one, for instance, it would immediately be bombed by Israel or become a nuclear superpower in a few weeks of operation.
- acidburnNSA 7y ago
  You can breed weaponizable fissile material in fast reactors. But by far the easiest way to make bomb material in a reactor is what they did in the Manhattan Project, using graphite moderated thermal neutron production reactors (not fast reactors). And it's even easier still to just build gas centrifuges and enrich uranium without needing a reactor at all. Becoming a nuclear superpower weeks after operation of a fast-neutron reactor is a bit of an overstatement.
acidburnNSA 7y ago
No. Weaponization of nuclear fission technology was completed in 1944. Plutonium production plants of similar design to those used in the Manhattan Project were used throughout the Cold War (at Hanford and Savannah River). There are myths about various nuclear technologies being cancelled because they "couldn't be weaponized" (usually talking about molten salt reactors), but these myths are quite wrong. Fast reactor tech hasn't been popular because it's more expensive than regular old water-cooled fission reactor tech. To keep neutrons going fast you have to use exotic coolants like sodium metal. Since you don't want to mix a chemical hazard with a radiological one, you insert an additional intermediate heat transfer loop into the system. Hot radioactive sodium transfers heat to hot non-radioactive sodium which transfers heat to water which boils and turns a turbine to crank a generator to push electrons around to provide low-carbon service to human quality of life.
- 08-15 7y ago
  Can you please not call sodium "exotic"? Doing so adds to an irrational fear of relatively benign technology. Molten sodium is easy to pump, non-corrosive to many metals including steel, and a good heat transfer medium. The chemical industry uses it routinely. In a nuclear reactor, it would also chemically sequester a particularly annoying fission product (I-131) in case of a fuel element leaking. Unpressurized, it is good up to 800C before it boils. By contrast, water at 300C will corrode most steels. At higher temperature, it will corrode zircalloy, forming hydrogen. And it really wants to be a gas, hence the giant containment buildings around LWR. What did you say? "But sodium explodes in contact with water?" That's easy to solve, just keep the water out. A sodium cooled reactor should be coupled to a supercritical CO2 turbine instead of a steam turbine. That removes the problem of leaking and exploding heat exchangers. (Footnote: I like molten salts better than sodium. But sodium is still better that water.)
  - acidburnNSA 7y ago
    Sodium coolant is exotic from an operational point of view. Exotic doesn't mean dangerous. Sodium systems from a probabilistic risk statement are usually 100x safer than pressurized systems because of passive decay heat removal capabilities. Exotic means "different from normal." So far, all operating sodium-cooled plants have suffered from operational and economic challenges due to sodium's characteristics. This is solvable with experience, but it's not easy. Have you ever studied a detailed procedure for heating up a large sodium valve from the solid sodium phase to the liquid? If not I highly recommend doing so. It's truly remarkable. Molten salt systems are the same level of complexity, but much more radioactive in the primary system. Remote maintenance of this stuff is totally doable, but it sure as hell is exotic. Rickover's characterization of sodium systems stands to this day. Traditional sodium systems with void-swelling resistant structural materials may not go to high enough temperatures to strongly justify the tech development needed for a sCO2 balance of plant in the short term. Sodium-water steam generators with leak detection have worked well-enough to build a few more of them while sCO2 turbomachinery gets figured out at the 100s of MW scale.

To the contrary. You can use these things to breed very dangerous material for bombs. Hence most industrial countries (say Germany) are nudged by the superpowers to not implement such devices. If Iran would build one, for instance, it would immediately be bombed by Israel or become a nuclear superpower in a few weeks of operation.

acidburnNSA 7y ago
You can breed weaponizable fissile material in fast reactors. But by far the easiest way to make bomb material in a reactor is what they did in the Manhattan Project, using graphite moderated thermal neutron production reactors (not fast reactors). And it's even easier still to just build gas centrifuges and enrich uranium without needing a reactor at all. Becoming a nuclear superpower weeks after operation of a fast-neutron reactor is a bit of an overstatement.

acidburnNSA 7y ago

No. Weaponization of nuclear fission technology was completed in 1944. Plutonium production plants of similar design to those used in the Manhattan Project were used throughout the Cold War (at Hanford and Savannah River). There are myths about various nuclear technologies being cancelled because they "couldn't be weaponized" (usually talking about molten salt reactors), but these myths are quite wrong. Fast reactor tech hasn't been popular because it's more expensive than regular old water-cooled fission reactor tech. To keep neutrons going fast you have to use exotic coolants like sodium metal. Since you don't want to mix a chemical hazard with a radiological one, you insert an additional intermediate heat transfer loop into the system. Hot radioactive sodium transfers heat to hot non-radioactive sodium which transfers heat to water which boils and turns a turbine to crank a generator to push electrons around to provide low-carbon service to human quality of life.

08-15 7y ago
Can you please not call sodium "exotic"? Doing so adds to an irrational fear of relatively benign technology. Molten sodium is easy to pump, non-corrosive to many metals including steel, and a good heat transfer medium. The chemical industry uses it routinely. In a nuclear reactor, it would also chemically sequester a particularly annoying fission product (I-131) in case of a fuel element leaking. Unpressurized, it is good up to 800C before it boils. By contrast, water at 300C will corrode most steels. At higher temperature, it will corrode zircalloy, forming hydrogen. And it really wants to be a gas, hence the giant containment buildings around LWR. What did you say? "But sodium explodes in contact with water?" That's easy to solve, just keep the water out. A sodium cooled reactor should be coupled to a supercritical CO2 turbine instead of a steam turbine. That removes the problem of leaking and exploding heat exchangers. (Footnote: I like molten salts better than sodium. But sodium is still better that water.)
- acidburnNSA 7y ago
  Sodium coolant is exotic from an operational point of view. Exotic doesn't mean dangerous. Sodium systems from a probabilistic risk statement are usually 100x safer than pressurized systems because of passive decay heat removal capabilities. Exotic means "different from normal." So far, all operating sodium-cooled plants have suffered from operational and economic challenges due to sodium's characteristics. This is solvable with experience, but it's not easy. Have you ever studied a detailed procedure for heating up a large sodium valve from the solid sodium phase to the liquid? If not I highly recommend doing so. It's truly remarkable. Molten salt systems are the same level of complexity, but much more radioactive in the primary system. Remote maintenance of this stuff is totally doable, but it sure as hell is exotic. Rickover's characterization of sodium systems stands to this day. Traditional sodium systems with void-swelling resistant structural materials may not go to high enough temperatures to strongly justify the tech development needed for a sCO2 balance of plant in the short term. Sodium-water steam generators with leak detection have worked well-enough to build a few more of them while sCO2 turbomachinery gets figured out at the 100s of MW scale.