[chris (OP)]

Some nuclear reactors are described as being "fast breeders" that can recycle fuel. How does this work?

Chris

[DoctorBeaver]

The reactor is surrounded by tubes containing Uranium²³⁸, which is non-fissile. The neutrons from the reaction interact with the U²³⁸ to produce U²³⁹ which is fissile and can then be used as fuel for the reactor.

[chris (OP)]

Sounds risky - could the reaction run-away with itself?

Chris

[DoctorBeaver]

No, because the U²³⁹ needs to be put into the reactor for fission to take place.

[syhprum]

The prototype fast breeder reactor at Dounray ran for 25 years with no reactor mishaps but was eventually abandoned due to waste handling mishaps and economic considerations.

[RD]

The prototype fast breeder reactor at Dounray ran for 25 years with no reactor mishaps
 but was eventually abandoned due to waste handling mishaps...

That's an understatement...

UK Atomic Energy Authority admitted that 170kg of weapons-grade enriched uranium had disappeared from Dounreay -
 enough to make a dozen atomic bombs.

http://news.bbc.co.uk/1/hi/uk/107158.stm

[rosalind dna]

Chris
In 1957 there was a huge reactor fire in Windscale (now called Sellafield) and caused loads of damage, that was until the
"Three Mile Island" reactor fire

http://en.wikipedia.org/wiki/Windscale_fire
http://en.wikipedia.org/wiki/Three_Mile_Island_accident

http://en.wikipedia.org/wiki/Sellafield

[Evie]

Chris
In 1957 there was a huge reactor fire in Windscale (now called Sellafield) and caused loads of damage, that was until the
"Three Mile Island" reactor fire

http://en.wikipedia.org/wiki/Windscale_fire
http://en.wikipedia.org/wiki/Three_Mile_Island_accident

http://en.wikipedia.org/wiki/Sellafield

Those were not breeder reactors, though, I believe.

[Xeon]

Some nuclear reactors are described as being "fast breeders" that can recycle fuel. How does this work?

Chris

hi , that is a confusing question .

[evan_au]

Sounds risky - could the reaction run-away with itself?

One of the problems with fast breeder reactors is that you need "fast" neutrons to convert abundant but non-fissile Uranium U238 into Plutonium Pu239 fuel.
- Conventional Uranium reactors use "slow" neutrons to cause fission of U235. They use a "moderator" like water; the neutrons bounce of the protons in the water (and to a lesser extent, the oxygen in the water), and slow down to a more moderate speed.
- In conventional reactors, water (or heavy water, in some designs) has the dual function of moderator and coolant

If you aren't going to use water as a moderator or a coolant, what do you use?
- Several designs have used molten sodium. This is incredibly reactive, and you can't put out any fires with water(!). This caused problems at the French Superphénix reactor.
- Other designs use molten lead as the coolant (eg Russian military reactors), molten salt, or helium gas

A more recent development is the Thorium breeder reactor, being actively investigated by India. This turns abundant but non-fissile Thorium Th232 into Uranium U233 fuel, and immediately burns it.
- It is claimed to be better protected against nuclear weapons proliferation, since it does not contain significant amounts of U235 or Pu239 (which could be made into the core of nuclear weapons).

See: https://en.wikipedia.org/wiki/Breeder_reactor#Fast_breeder_reactor
https://en.wikipedia.org/wiki/Superph%C3%A9nix

[Petrochemicals]

Chris
In 1957 there was a huge reactor fire in Windscale (now called Sellafield) and caused loads of damage, that was until the
"Three Mile Island" reactor fire

http://en.wikipedia.org/wiki/Windscale_fire
http://en.wikipedia.org/wiki/Three_Mile_Island_accident

http://en.wikipedia.org/wiki/Sellafield

Those were not breeder reactors, though, I believe.

Windscale was a weapon producer, maybe not a uranium breeder but a breeder, designed for producing material for the weapons. The fire came about because of the( 1958? ,) morotorium on atmospheric testing, Britain wished to demonstrate Hydrogen bomb capability to the USA for some reason, the need for nuclear material before the test cut off (1962) made them run the reactor fast and led to a melt down. Windscale was not optimised for electric.

[Bored chemist]

the need for nuclear material before the test cut off (1962) made them run the reactor fast and led to a melt down.

The reactor didn't melt down.
What did for it was Wigner energy.

Part of the problem was that they didn't have a chemist, a gardener, a boy-scout  or a barbeque cook present.

Any of that group could have told them that if you have red hot charcoal and you blow on it, it doesn't get cooler.
But they had nuclear physicists...

[Petrochemicals]

As a further point the uk failed to produce the h bomb but demonstrated a boosted fission bomb which was good enough for the USA to open the door that they had shut after ww2 on the British started and developed nuclear bomb programme.

Also the nuclear test ban coincides with bad winters in the UK and america

[evan_au]

the Thorium breeder reactor, being actively investigated by India

Thorium reactors were investigated by the major nuclear powers, but discarded.

Cynics would argue that the current dominance of Uranium reactors is because the military used them to produce plutonium for weapons, creating a pool of people experienced with Uranium reactors.
- Since Thorium reactors don't produce useful amounts of fissile material, they would be of no interest to the military, and were quickly discarded
- Hence the problem we have today with risks (or actual) nuclear proliferation associated with Uranium reactors, eg the current standoff with Iran

See: https://en.wikipedia.org/wiki/Thorium-based_nuclear_power

Cynic - who, me?

[Petrochemicals]

the Thorium breeder reactor, being actively investigated by India

Thorium reactors were investigated by the major nuclear powers, but discarded.

Cynics would argue that the current dominance of Uranium reactors is because the military used them to produce plutonium for weapons, creating a pool of people experienced with Uranium reactors.
- Since Thorium reactors don't produce useful amounts of fissile material, they would be of no interest to the military, and were quickly discarded
- Hence the problem we have today with risks (or actual) nuclear proliferation associated with Uranium reactors, eg the current standoff with Iran

See: https://en.wikipedia.org/wiki/Thorium-based_nuclear_power

Cynic - who, me?

Truthfully Evan I think  you have to balance how much radioactive waste is produced, France who went for nuclear in a big way has a serious problem, the sheer cost of nuclear waste  management does not seem to be factored. Granted a thorium reactor will produce less high level waste, but will it produce more low level waste per kwh?

[yor_on]

You shouldn't get stuck on Thorium. Look at molten salt reactors instead.
https://www.theguardian.com/environment/2011/jun/23/thorium-nuclear-uranium

http://large.stanford.edu/courses/2015/ph240/dodaro2/
=

And using it should be considered a transitionary period. We need it, at least as I look at it, to handle ourselves for the next fifty, hundred years or so. Once the population curve goes down we can dismantle them in favor for decentralized solutions not using and creating radioactive materials. We should be able to change our infra structures by then. And we can use weapon plutonium for them too meaning that, if we want, we could get rid of a lot of those f*ng nuclear bombs and missiles.

you already have that in conventional reactors, called 'MOX' but it's a lot more unstable process as I understands it than using it in a Molten salt reactor. https://en.wikipedia.org/wiki/MOX_fuel