Doug Coulter wrote:So far it seems all these guys are testing with DD, then extrapolating to DT, which of course makes much nastier fast neutrons.
As far as I am aware to date, there are only two facilities set up to handle tritium, and these are JET and TFTR.
For the remainder of the tokamaks, again as far as I know, the majority actually don't even run DD - they are all H [or other heavier gases] plasma experiments. Just...plasma....experiments....
JET has run two experimental 'campaigns' on tritium over the years, but most is still H or DD. I'm lead to believe the reason is actually a little more mundane than an issue with getting or handling tritium - JET has a lifetime budget of 2E21 neutrons permitted. (I think this neutron budget figure is due to total activation and permitted displacements per atom in the structure.) It has got most of those from the DT experiments. So it runs DD to keep the total neutron emissions down, which is currently one tenth of that budget. I believe the aim is to finish its days (which I think is planned for only a few more years) with more DT experiments.
Doug Coulter wrote:They are planning to breed the T in a 6Li blanket material, using unspecified "neutron multipliers" as they need more neutrons to breed T than the DT reaction makes, or more accurately, they won't capture the required 100% of them needed to breed enough T, assuming zero losses of it.
I've asked the ITER press office about what plans there are for the blanket experiments and...get this... there are currently
no plans. They are still talking about it and there is not yet a specific objective to run a blanket with ITER! So here we have an experiment that potentially is to demonstrate viable fusion, but that they have not yet planned the experiments to show viable fusion (as it isn't viable without tritium breeding).
That's not to say they won't put it in place sometime in the decades-long timescales of ITER, but I was surprised when I was told that!
I do not believe ITER is actually a good scientific experiment because the objectives are unclear. It is a load of activity to make a big tokamak. What is the objective? I've directly suggested that it is off-message and that if it were really to show tokamak power stations can work then it should be 100% directed to a machine that pumps out energy. They are planning to spend years on investigating special materials when, in actual fact, they could make not just this but jump to a DEMO version, making the darned thing out of stainless steel, run it at net-power, and then have proved the experiment. Once they are making net energy, solutions would be found to overcome all the other issues quick enough... once folks can be confident that there
really is a power station at the end of the effort. So why are they wasting time on exploring materials when they could get busy building a bigger version of JET in a quarter of the time at a quarter of the budget to prove viable over unity power? Sure, they'll end up with a slightly more activated pile of scrap than if they spent an extra 20 years investigating low activation materials, but if my suggestion was followed, to go straight for a DEMO power station out of stainless steel and run it for a few months to show it
could be done, the stuff would probably not even be radioactive after that long!!!!
It's almost as if whoever is actually running the project has decided it's going to work and that they actually delude themselves to think the only remaining issues are engineering ones. I'm afraid that my opinion is that no-
one is actually in charge of this runaway gravy-train and no-one knows where the brakes are even if they figured out there are better ways to approach the experiment.
Surely the experimental objective is to prove magnetic confinement can be used as the basis of a fusion power station. ITER, alone, cannot do this, so why is it being done? DEMO, the one that is meant to come after ITER [if it is successful] can show this, so why not just go for DEMO?