TallDave wrote:What worries me about their solution is that they are talking about bleeding off energy from the plasma to solve this. Given that the whole challenge in a maxwellian setup like a tokamak is to confine as much energy in as small an area as possible, the fact they are resorting to leaking some out doesn't seem to bode well.
The whole ergosity thing is not a bad idea, when conducted carefully it won't reduce confinement time, it will only smooth it out. In between ELMS ergosity will reduce confinement a little but since during ELMs confinement is reduced without ergosity, since ideally ergosity stops ELMs it will increase the confinement over the would-be elming periods.
This ergosity thing isn't something completely out of the blue, its been tried and tested on D-IIID already. As to the reason why the problem of ELMS has suddenly come to the for front as a potential problem with the ITER design, IMO it is because they have just come up with a solution. The ITER team don't like to go to the press with problems when no obvious solution exists, there are probably plenty of problems to do with ITER for which the solution is not obvious but people are just discretely staying quite about and hoping for the best.
That 9 GJ figure sounds about right, at beta=5% 640MJ sounds more like the internal energy of the plasma, I heard that the magnetic energy stored in ITER will be the equivalent of 1/40 of the Hiroshima bomb (if released suddenly), this isn't the same as the power dissipation however, as the coils are super-conducting and so don't require any power to maintain their magnetic field. That will be the real challenge, making sure the thing doesn't break. So long as they can keep tinkering around with the plasmas I'm pretty sure they get their Q=10 objective atleast, but if the vacuum vessel cracks open releasing tritium rich Berilium Dust all over Cadarache.......... I can just see the headlines in large bold print: "Clean, safe energy?"
Incidentally, regarding a sudden release of heat, you might want to consider the issue of wigner energy. As the neutrons pour through ITER, defects buildup in the materials, these defects have a potential energy associated with them, if they are heated above a critical threshold this energy can be suddenly released in one go, it this release is too great for the coolant which cools the super conducting magnets to handle then they could be carried above the critical temperature which might result in a thermal quench... this would not be good. (Although the super conducting coils are embedded it copper which has a low resistance and therefore should inductively slow down such a quench)
By the way, I've talked to some people who work on the design of the blankets and they will
not contain liquid lithium, its far too volatile, there are non-explosive solutions to blanket design in with the lithium atoms are present in more stable compounds. There are also smart ways of reducing the buildup of non-tritium radioactive compounds... its not
that bad!
Incidentally I don't share the view that ITER won't be built or funding will suddenly be cut, Europe's in it too deep. After that quibble with Japan the EU is now footing 60% of the bill, I think the EU will build ITER whether or not the rest of the world wants to get involved.