Just a note that a magnetically confined fusion plasma is a LOW DENSITY system, with IIRC typical electron/ion densities in the 10E13-10E14 per cubic cm region, and tempetures of only around 10Kev. Getting any one (or possibly) two parameters into the useful fusion region is easy, getting all three there is a hard problem!
Even in the event of a leak to atmosphere, air (and worse, water vapour - time consuming to pump back out) will flow into the reaction chamber and will very quickly quench the plasma.
IIRC Argon has been used to deliberately quench the plasma in some experimental reactors so as to avoid wall erosion during an instability?
The failiure mode that is likely to cause far more damage to the machine is it seems to me a sudden failiure of the magnet assembly as that would dump the whole 1.2LI^2 energy from the magnetic field into the structure and while I don't have figures for the energy stored in this mechanism, I am willing to bet that it is far larger then energy stored in the plasma.
It is somewhat difficult to see a failiure mode that would have much effect outside the plant, possibly a tritium leak or major liquid metal fire, but tritium has a fairly short half life (14 years), and has a short biological half life (unless as tritium hydroxide, T2O or DTO, T2O is corrosive, so is not favoured as an approach to storage, DTO might be a reasonable way to store fusion fuel, but for these experimental reactors, I am betting that a uranium hydride will be used, with the tritium released by heating).
Note that none of this says that a radiation release is impossible, the reactor structure will after all be exposed to a considerable neutron flux (and there will be some local X ray hazard inside the sheilding while the plasma is present).
There is IMHO lots of interesting engineering (and a lot of interesting physics) in the details of these machines.
Slashdot Mirror
Just a note that a magnetically confined fusion plasma is a LOW DENSITY system, with IIRC typical electron/ion densities in the 10E13-10E14 per cubic cm region, and tempetures of only around 10Kev. Getting any one (or possibly) two parameters into the useful fusion region is easy, getting all three there is a hard problem!
Even in the event of a leak to atmosphere, air (and worse, water vapour - time consuming to pump back out) will flow into the reaction chamber and will very quickly quench the plasma.
IIRC Argon has been used to deliberately quench the plasma in some experimental reactors so as to avoid wall erosion during an instability?
The failiure mode that is likely to cause far more damage to the machine is it seems to me a sudden failiure of the magnet assembly as that would dump the whole 1.2LI^2 energy from the magnetic field into the structure and while I don't have figures for the energy stored in this mechanism, I am willing to bet that it is far larger then energy stored in the plasma.
It is somewhat difficult to see a failiure mode that would have much effect outside the plant, possibly a tritium leak or major liquid metal fire, but tritium has a fairly short half life (14 years), and has a short biological half life (unless as tritium hydroxide, T2O or DTO, T2O is corrosive, so is not favoured as an approach to storage, DTO might be a reasonable way to store fusion fuel, but for these experimental reactors, I am betting that a uranium hydride will be used, with the tritium released by heating).
Note that none of this says that a radiation release is impossible, the reactor structure will after all be exposed to a considerable neutron flux (and there will be some local X ray hazard inside the sheilding while the plasma is present).
There is IMHO lots of interesting engineering (and a lot of interesting physics) in the details of these machines.