4 ms·

I had heard that one of the major drawbacks of tokamaks was the incredible temperatures lead to situations where the smallest mechanical failure will lead to an

I had heard that one of the major drawbacks of tokamaks was the incredible temperatures lead to situations where the smallest mechanical failure will lead to an explosion of hot, radioactive gas. Is that not the case?

ncmncm 5y ago
That would be the least of its problems. Costing hundreds or thousands of times as much as solar + storage is a more serious problem. Since it won't be built, that is a theoretical problem. But the project can absorb an unlimited amount of money first.
pas 5y ago
The whole amount of gas in the chamber is just a few grams. Tritium is not pleasant though, but veeeeeeeeery far from anything that could do real harm: https://en.wikipedia.org/wiki/Tritium#Health_risks https://en.wikipedia.org/wiki/Tritium#Health_risks (you'd need to leak a lot of it continuously)
rnhmjoj 5y ago
Temperature is not a very good quantity to gain intuition about plasmas (or heat transfer in general): the temperature of the electrons in a incandescent light bulb is around 10000 K, which seems very hot, but since their density is much lower than the air density, the powers involved are quite small and a light bulb is pretty safe to touch. In the same way, a fusion plasma doesn't hold that much energy because of the extremely low density (4×10^-6 that of air). An explosion (a runaway/chain reaction) is also not possible: the reactor must continuously supplied with fuel or the fusion reactions will stop in a matter of seconds. There are situations which could result in significant damage to the reactor components, but still not a public safety concern. Distruptions are events in which the plasma confinement is lost and a large amount of heat is released that could damage all components that face the plasma, but reactors are designed to withstand this. Another drawback, if you like, are runaway electrons, which are populations of relativistic particles that become unbound and penetrare the vacuum vessel for several mm. Again, this is not a particular issue from a safety point of view, but they can do a lot of damage: if they hit a magnetic coil and cause a loss of the superconductivity state, the coil can heat very rapidily (due to the huge current that goes through it) and potentially melt. Replacing such a coil could cost years of maintenance, for this reason reactors are build with many fallback systems.

ncmncm 5y ago

That would be the least of its problems. Costing hundreds or thousands of times as much as solar + storage is a more serious problem. Since it won't be built, that is a theoretical problem. But the project can absorb an unlimited amount of money first.

pas 5y ago

The whole amount of gas in the chamber is just a few grams. Tritium is not pleasant though, but veeeeeeeeery far from anything that could do real harm: https://en.wikipedia.org/wiki/Tritium#Health_risks https://en.wikipedia.org/wiki/Tritium#Health_risks (you'd need to leak a lot of it continuously)

rnhmjoj 5y ago

Temperature is not a very good quantity to gain intuition about plasmas (or heat transfer in general): the temperature of the electrons in a incandescent light bulb is around 10000 K, which seems very hot, but since their density is much lower than the air density, the powers involved are quite small and a light bulb is pretty safe to touch. In the same way, a fusion plasma doesn't hold that much energy because of the extremely low density (4×10^-6 that of air). An explosion (a runaway/chain reaction) is also not possible: the reactor must continuously supplied with fuel or the fusion reactions will stop in a matter of seconds. There are situations which could result in significant damage to the reactor components, but still not a public safety concern. Distruptions are events in which the plasma confinement is lost and a large amount of heat is released that could damage all components that face the plasma, but reactors are designed to withstand this. Another drawback, if you like, are runaway electrons, which are populations of relativistic particles that become unbound and penetrare the vacuum vessel for several mm. Again, this is not a particular issue from a safety point of view, but they can do a lot of damage: if they hit a magnetic coil and cause a loss of the superconductivity state, the coil can heat very rapidily (due to the huge current that goes through it) and potentially melt. Replacing such a coil could cost years of maintenance, for this reason reactors are build with many fallback systems.