4 ms·

I could imagine that the fuel supply getting jammed on is not so dissimilar from the control rods being jammed out.

altec3 7y ago
Armchair opinion: I believe the fuel isn't radioactive, and neither is the reaction. So while it could blow up, it's not going to have a ton of radioactive fallout. Sort of like a fusion bomb, the fusion bomb doesn't produce radioactive fallout, but the fission bomb necessary to start the fusion bomb does.
- sbierwagen 7y ago
  D-T fusion, which ITER will use, produces neutron radiation, which will cause neutron activation in reactor components, rendering them radioactive: https://en.wikipedia.org/wiki/Neutron_activation https://en.wikipedia.org/wiki/Neutron_activation Aneutronic fusion is possible, but requires collision energies much higher than what ITER is designed to create.
  - Symmetry 7y ago
    In theory you can chose construction materials that don't do anything too horrible when you bang them with neutrons in the construction of your fusion reactor. I'm not sure how well this is achievable in practice in the construction of a fusion reactor but I'm pretty sure they can avoid using anything that creates byproducts as nasty as uranium does. EDIT: I do wonder if there's a danger of nuclear proliferation with using fusion reactors to breed plutonium from natural uranium, though.
- noobermin 7y ago
  Yes and no. Depending on the fusion process, the fuel can be radioactive: DT for example, Tritium, Hydrogen-3 is a beta emitter. But it certainly isn't as bad of a thing especially compared to Uranium and friends. EDIT: see other comment, DT produces neutrons which can be bad, I still think the amount nastiness is small compared to say Chernobyl.
  - xyzzyz 7y ago
    > But it certainly isn't as bad of a thing especially compared to Uranium and friends. Tritium is something like 10 orders of magnitude more radioactive than uranium (in terms of its specific activity). Uranium itself is so low in radioactivity that the bigger risk when handling it is heavy metal poisoning. The by-products of fissions are much more radioactive, though.
    - noobermin 7y ago
      The by-products is what I meant when I said Uranium and friends.
- Symmetry 7y ago
  If you set of a thermonuclear bomb in the middle of the air you'll get a bit of fallout from the primary stage that sets it off, the secondary, fusion, stage will produce a bunch of neutrons but no fallout, and the third, depleted uranium, stage will absorb all the neutrons from the fusion and produce a fair amount of fallout. A lot of neutrons will escape and interact with the air but none of the elements you find in the atmosphere turns into anything much worse than deuterium or carbon-14 when you whack it with a neutron so overall its fine. You can replace the third stage with lead and lose half the explosive force but gain an almost entirely clean explosion. If you set it off near the ground many of the escaping neutrons will interact with things that get very angry when activated by a stray neutron. A big bomb detonated near the ground, to crack open a bunker for instance, can send stupendous amounts of fallout into the air and kill people hundreds of miles down wind of acute "vomit now and die in a week" radiation poisoning.
Ididntdothis 7y ago
It’s more like the fuel pump of your car breaking.
bsder 7y ago
No. Too many fusion nuclei will destabilize the plasma as quickly as too few. Fusion is about hitting a precise balance point. It's why it's so hard.
petschge 7y ago
If your supply of Deuterium and Tritium was jammed wide open you, would stop the fusion (either by switching of the heating if you are in startup or by messing with the magnetic confinement to make the plasma hit the diverter). At that point all you do is pumping low density, relatively low radioactivity gases into a large gas proof vacuum vessel. No explosion, no meltdown, no release of radioactivity to the containment building let along the environment. As far as worst case scenarios go it is pretty harmless. The entire ITER site will never store more than 4kg of tritium, most in the form of metal-hydrites.
zaarn 7y ago
Too much fuel would estinguish the fire, similar to too much fuel in a car engine will cause it to stall. The high temperatures necessary for fusion are only attainable at low masses, if too much fuel enters the reactor, it cools down and becomes inert. The fuel itself is not radioactive and safe for consumption in reasonable amounts (heavy water inhibits biological processes if it becomes too much in concentration, but unless you drink straight from the heavy water tanks for days, this is essentially not an issue)

Armchair opinion: I believe the fuel isn't radioactive, and neither is the reaction. So while it could blow up, it's not going to have a ton of radioactive fallout. Sort of like a fusion bomb, the fusion bomb doesn't produce radioactive fallout, but the fission bomb necessary to start the fusion bomb does.

sbierwagen 7y ago
D-T fusion, which ITER will use, produces neutron radiation, which will cause neutron activation in reactor components, rendering them radioactive: https://en.wikipedia.org/wiki/Neutron_activation https://en.wikipedia.org/wiki/Neutron_activation Aneutronic fusion is possible, but requires collision energies much higher than what ITER is designed to create.
- Symmetry 7y ago
  In theory you can chose construction materials that don't do anything too horrible when you bang them with neutrons in the construction of your fusion reactor. I'm not sure how well this is achievable in practice in the construction of a fusion reactor but I'm pretty sure they can avoid using anything that creates byproducts as nasty as uranium does. EDIT: I do wonder if there's a danger of nuclear proliferation with using fusion reactors to breed plutonium from natural uranium, though.
noobermin 7y ago
Yes and no. Depending on the fusion process, the fuel can be radioactive: DT for example, Tritium, Hydrogen-3 is a beta emitter. But it certainly isn't as bad of a thing especially compared to Uranium and friends. EDIT: see other comment, DT produces neutrons which can be bad, I still think the amount nastiness is small compared to say Chernobyl.
- xyzzyz 7y ago
  > But it certainly isn't as bad of a thing especially compared to Uranium and friends. Tritium is something like 10 orders of magnitude more radioactive than uranium (in terms of its specific activity). Uranium itself is so low in radioactivity that the bigger risk when handling it is heavy metal poisoning. The by-products of fissions are much more radioactive, though.
  - noobermin 7y ago
    The by-products is what I meant when I said Uranium and friends.
Symmetry 7y ago
If you set of a thermonuclear bomb in the middle of the air you'll get a bit of fallout from the primary stage that sets it off, the secondary, fusion, stage will produce a bunch of neutrons but no fallout, and the third, depleted uranium, stage will absorb all the neutrons from the fusion and produce a fair amount of fallout. A lot of neutrons will escape and interact with the air but none of the elements you find in the atmosphere turns into anything much worse than deuterium or carbon-14 when you whack it with a neutron so overall its fine. You can replace the third stage with lead and lose half the explosive force but gain an almost entirely clean explosion. If you set it off near the ground many of the escaping neutrons will interact with things that get very angry when activated by a stray neutron. A big bomb detonated near the ground, to crack open a bunker for instance, can send stupendous amounts of fallout into the air and kill people hundreds of miles down wind of acute "vomit now and die in a week" radiation poisoning.

Ididntdothis 7y ago

It’s more like the fuel pump of your car breaking.

bsder 7y ago

No. Too many fusion nuclei will destabilize the plasma as quickly as too few. Fusion is about hitting a precise balance point. It's why it's so hard.

petschge 7y ago

If your supply of Deuterium and Tritium was jammed wide open you, would stop the fusion (either by switching of the heating if you are in startup or by messing with the magnetic confinement to make the plasma hit the diverter). At that point all you do is pumping low density, relatively low radioactivity gases into a large gas proof vacuum vessel. No explosion, no meltdown, no release of radioactivity to the containment building let along the environment. As far as worst case scenarios go it is pretty harmless. The entire ITER site will never store more than 4kg of tritium, most in the form of metal-hydrites.

zaarn 7y ago

Too much fuel would estinguish the fire, similar to too much fuel in a car engine will cause it to stall. The high temperatures necessary for fusion are only attainable at low masses, if too much fuel enters the reactor, it cools down and becomes inert. The fuel itself is not radioactive and safe for consumption in reasonable amounts (heavy water inhibits biological processes if it becomes too much in concentration, but unless you drink straight from the heavy water tanks for days, this is essentially not an issue)