Eli5 How does nuclear fuel get spent so fast?

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With the half life of the radioactive metals used in the fuel rods being thousands of years, the fuel used in reacors, i would think, should last for similar amounts of time. How come nuclear plants go through large ammount of spent fuel that then has to be stored?

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Anonymous 0 Comments

Because inside the reactor we use unnatural practices to slow the neutrons down so they collide into each other and create fission.

Anonymous 0 Comments

Because inside the reactor we use unnatural practices to slow the neutrons down so they collide into each other and create fission.

Anonymous 0 Comments

Because inside the reactor we use unnatural practices to slow the neutrons down so they collide into each other and create fission.

Anonymous 0 Comments

The half-life is due to spontaneous decay. They’re kind of unstable so there is a chance of them just going “poof” and decaying. Half-life is the time it takes for half of the atoms in any given amount of material to undergo this spontaneous decay.

However, in a reactor we’ve arranged it so that there is a pretty big chance that when one atom decays the neutron (small sub-atomic particle) shoots out and hits another atom, which will cause that atom to split and shoot off more neutrons, which will hit other particles and cause a cascade effect. Compare it to just shooting a billiard ball on a pool table randomly vs stacking the balls into a pyramid (shooting a ball into that pyramid will cause a whole bunch of other balls to move around).

That effect is used in a reactor, because when a whole bunch of little atoms decay quickly they release heat. In our normal powerplants they’re stacked so that it happens very quickly (although our current generation is kind of inefficient and only a small percentage of the fuel is used up before the effect slows down or becomes too difficult to handle due to dangerous byproducts), and that generates a lot of heat which is used to heat water into steam and drive a steam turbine.

There is also something called a radioisotope thermoelectric generator, a nuclear battery of sorts. Basically a radioactive element that has been arranged to encourage it to just react a little bit faster. Not cascade, just generate enough heat that it can be used to generate power through the thermoelectric effect. Those batteries last a lot longer, so they’re used on deep space satellites like Voyager (that travel far enough away from the sun that solar panels aren’t useful anymore). Voyagers nuclear battery produced something like 60% of its original power back in 2001 (some 25 years after its launch) but theoretically a battery like this could be designed to last thousands of years.

Anonymous 0 Comments

The half-life is due to spontaneous decay. They’re kind of unstable so there is a chance of them just going “poof” and decaying. Half-life is the time it takes for half of the atoms in any given amount of material to undergo this spontaneous decay.

However, in a reactor we’ve arranged it so that there is a pretty big chance that when one atom decays the neutron (small sub-atomic particle) shoots out and hits another atom, which will cause that atom to split and shoot off more neutrons, which will hit other particles and cause a cascade effect. Compare it to just shooting a billiard ball on a pool table randomly vs stacking the balls into a pyramid (shooting a ball into that pyramid will cause a whole bunch of other balls to move around).

That effect is used in a reactor, because when a whole bunch of little atoms decay quickly they release heat. In our normal powerplants they’re stacked so that it happens very quickly (although our current generation is kind of inefficient and only a small percentage of the fuel is used up before the effect slows down or becomes too difficult to handle due to dangerous byproducts), and that generates a lot of heat which is used to heat water into steam and drive a steam turbine.

There is also something called a radioisotope thermoelectric generator, a nuclear battery of sorts. Basically a radioactive element that has been arranged to encourage it to just react a little bit faster. Not cascade, just generate enough heat that it can be used to generate power through the thermoelectric effect. Those batteries last a lot longer, so they’re used on deep space satellites like Voyager (that travel far enough away from the sun that solar panels aren’t useful anymore). Voyagers nuclear battery produced something like 60% of its original power back in 2001 (some 25 years after its launch) but theoretically a battery like this could be designed to last thousands of years.

Anonymous 0 Comments

The half-life is due to spontaneous decay. They’re kind of unstable so there is a chance of them just going “poof” and decaying. Half-life is the time it takes for half of the atoms in any given amount of material to undergo this spontaneous decay.

However, in a reactor we’ve arranged it so that there is a pretty big chance that when one atom decays the neutron (small sub-atomic particle) shoots out and hits another atom, which will cause that atom to split and shoot off more neutrons, which will hit other particles and cause a cascade effect. Compare it to just shooting a billiard ball on a pool table randomly vs stacking the balls into a pyramid (shooting a ball into that pyramid will cause a whole bunch of other balls to move around).

That effect is used in a reactor, because when a whole bunch of little atoms decay quickly they release heat. In our normal powerplants they’re stacked so that it happens very quickly (although our current generation is kind of inefficient and only a small percentage of the fuel is used up before the effect slows down or becomes too difficult to handle due to dangerous byproducts), and that generates a lot of heat which is used to heat water into steam and drive a steam turbine.

There is also something called a radioisotope thermoelectric generator, a nuclear battery of sorts. Basically a radioactive element that has been arranged to encourage it to just react a little bit faster. Not cascade, just generate enough heat that it can be used to generate power through the thermoelectric effect. Those batteries last a lot longer, so they’re used on deep space satellites like Voyager (that travel far enough away from the sun that solar panels aren’t useful anymore). Voyagers nuclear battery produced something like 60% of its original power back in 2001 (some 25 years after its launch) but theoretically a battery like this could be designed to last thousands of years.

Anonymous 0 Comments

The nuclear fuel used in reactors gets spent quickly because the fission process breaks the atoms apart, releasing energy and creating radioactive byproducts that can interfere with the reaction. It’s like burning wood in a fire — it’s gone quickly because the chemical reaction releases energy and changes the wood into ash.

Anonymous 0 Comments

The nuclear fuel used in reactors gets spent quickly because the fission process breaks the atoms apart, releasing energy and creating radioactive byproducts that can interfere with the reaction. It’s like burning wood in a fire — it’s gone quickly because the chemical reaction releases energy and changes the wood into ash.

Anonymous 0 Comments

The nuclear fuel used in reactors gets spent quickly because the fission process breaks the atoms apart, releasing energy and creating radioactive byproducts that can interfere with the reaction. It’s like burning wood in a fire — it’s gone quickly because the chemical reaction releases energy and changes the wood into ash.

Anonymous 0 Comments

Think of it like a bunch of dominoes standing on end – and “half-life” is how long it typically takes half of all independent dominos to tip over because of a tiny breeze, etc.

If these dominoes are set up very far apart, then one domino randomly tipping over only releases a tiny amount of kinetic energy and isn’t likely to knock any others over. This is where the natural independent “radioactive decay” idea comes into play, and is how “half-life” is defined.

On the other hand, if there are very many dominoes standing next to each other, then one domino tipping over might push two others, which might push into four others, with might push into eight others, etc. All of these dominoes (except the very first one) didn’t “decay” naturally, they were all pushed! So, the amount of fallen dominoes is more a question of “How closely packed are the dominoes?” and “How long on average does a chain-reaction of domino falls last?” rather than a question of isolated “half-life”.

Nuclear reactors burn through fuel quickly compared to the fuel half-life because they are designed to sustain those long chain-reactions that release more energy faster.