Hotter than the Sun: JET – Earth’s biggest fusion reactor, in Culham

Re: Didn't they used to have a flywheel?

I remember being told about the flywheel at a school talk.

IIRC we were told it took a couple of days to get up to speed and if it ever came away from it's bearings it would go all the way to Reading, smash through the centre and keep going.

Not all bad then....

Re: Didn't they used to have a flywheel?

Yes, I think they had two concrete flywheels run up to speed at 200 rpm by electric motor & suppelemnted about 600Mw from the Didcott to Cowley supergrid.

I visited some time around 1990 & very interesting it was too. Aparently they also had to let Dinorwig know otherwise it cut in on the dip.

Re: Didn't they used to have a flywheel?

On an open day once, long ago, I got to go inside the flywheel enclosure. They'd done a run not many days before, and it was still roasting hot in there. This was before they'd started using tritium, so they'd opened up the pressure vessel so that you could see inside, and get quite close to it. Very impressive! I grew up near there, and remember the lights dimming whenever JET started up (or at least that's what we assumed it was!).

It's interesting to compare political priorities. Fusion may one day provide us with power, and if it works at any decent scale it will be the power source of choice for pretty much the rest of time. The geopolitical consequences will be immense (and mostly good, I hope). Energy supply underpins pretty much everything else. So given that, you'd think that it would be high up on the politicians priority list?

Nope. ITER is costing a few €billion. Compare that to saving the banks in 2007 / 2008. Gordon Brown when prime minister all on his own managed to spend £150billion in a single afternoon saving the banks, enough to pay for and accelerate the entire ITER project several times over.

I'm not suggesting that saving the banks was a bad idea (a debate for another day...), but the first hint that fusion actually works ought to liberate rather more enthusiasm, cash and effort. There's a lot that has been achieved by JET (it's ended up massively exceeding what they were planning on back in the 1970s), and I think it right that ITER is being seen more as an engineering project than a research project. Compared to saving the banks, you'd think it'd be worth putting a few more quid into ITER.

Re: Didn't they used to have a flywheel?

There are two flywheels, one to drive the Toroidal Coils that contain the plasma, one to drive the central solenoid that drives the plasma current (think of a tokamak as a giant sparkplug). It takes a couple of minutes to spin them up from 80rpm to the operating speed. However, there are also power amplifiers driving coils that control the plasma shape and position, and most of the energy going into the plasma while the actual science is happening comes from the additional heating systems, neutral particle beams and radio frequency heating, and these are all driven off the national grid.

Re: flywheel safety

Could the flywheels not be sited such that they are in a pit ?

Re: So still 20 years in the future...?

Yes, 100 years ago.

Re: So still 20 years in the future...?

I'm pretty sure it was always 30 years in the future 20 years ago. It looks like we may be asymptotically approaching 0 years ...

Re: Fun times....

"... castor oil, which was the electrolyte used"

It was a dielectric. Just saying.

Re: Fun times....

I visited Culham in 1966.

Years before we joined the 'common market'

However did it get paid for?

Re: "The fission process turns two forms of hydrogen"

> Is it the neutrons that can generate power, or the the helium too?

The neutrons pass out of the magnetic fields because they are neutral, and strike atoms in the lining of the torus. These then undergo radioactive funtimes and release heat that's used to generate electricity.

Well, that's my understanding of the technology, anyway. And it does mean that running a De/Tr test makes the interior of the torus radioactive, yes. It's one of the reasons the research is *expensive*.

Re: Brexit pushes Fusion Power back another 10 years

Which is incredibly restrained of it, especially given that it pushes national attitudes to racism back 60 years, and the economy back 40 years. I’d say Fusion is getting off remarkably lightly.

Re: Snake Oil

"Its always 20 years to success or anything near that since last few decades."

Depends on your definition of success...

Have you seen the list of spinoff technologies developed?

Re: Snake Oil

Ahem. Superconducting magnets.

Re: Snake Oil

"To contain semiconducting magnets which are cooled to near absolute 0."

Well 4K to be exact, and that is a huge difference between that and near absolute 0. This is quite easy to achieve (see CERN), and once obtained as long as well insulated very easy to maintain with minimum of energy expenditure

"To extract any usable heat no way to sustain leak and keep reactor ongoing."

Well, that's the challenge isn't it, but it is an engineering issue, not one of basics physics and solving the engineering is why ITER is being built. The only way we will know whether it is possible is to try. The alternative is to give up when things get hard. The reason we keep trying is the rewards for success are so huge

"Its always 20 years to success or anything near that since last few decades."

That ignores the amount of progress made in the last 20 years. Not only that but technology moves onwards. High temperature magnets, advanced computer control and modelling, improved material science provides capabilities that were only a pipe dream 20 years ago. That is why they have the confidence to move from experiment to full scale engineering demonstrator.

That is not to pretend of the challenges. This is the energy moonshot, but the potential rewards are so huge, it makes it worth trying.