Fusion “breakthrough” is largely irrelevant to the climate crisis.  « nuclear-news

Fusion “breakthrough” is largely irrelevant to the climate crisis. 

Gordon Edwards 15 Dec 22

Just a short commentary on the  “fusion breakthrough” this week.
The experiment took place at the Lawrence Radiation Lab, a pre-eminent weapons Laboratory in California once directed by Edward Teller.

Jubilation is felt because, for the first time in over 60 years of effort costing many billions of dollars, a greater amount of energy came  out of an extremely short-lived fusion reaction than the amount of energy needed to trigger it in the first place. The net energy gain was about 50 percent.

It all happened very quickly. “The energy production took less time than it takes light to travel one inch,” said Dr Marvin Adams, at the NNSA.  (NNSA = National Nuclear Security Administration)

Here are a few details –

1) In an earlier email (www.ccnr.org/fission_fusion_and_efficiency_2022.pdf )I described the “magnetic confinement” concept, whereby an electromagnetic force field holds a very hot plasma of hydrogen gases inside a doughnut-shaped torus (typical of the Tokamak and its close relatives). In this case, “very hot”. Means about 150 million degrees C.  

But the breakthrough that is being bally-hooed now, since Tuesday December 13, is a different kind of process altogether, using a concept called “inertial confinement”.

The experiment involved a small pellet about the size of a peppercorn. This pellet contained, in its interior, a mixture of deuterium and tritium gases, two rare hydrogen isotopes.  In the experiment, the pellet’s exterior was blasted by x-rays triggered by a battery of 192 very powerful lasers, all targeted on the inner walls of a cylinder made of gold. The lasers generated x-rays on contact with the goldatoms, and those x-rays were focussed by the curving cylinder walls on the little peppercorn-sized pellet in the middle of the gold cylinder.

The x-rays heated the outer shell of the pellet to more than three million degrees, making the exterior of the pellet explode outwards, and (by Newtons “action-reaction” principle) causing the inner gases to be compressed to a very high density at an extremely high temperature, presumably to over 100 million degrees. It is a high-energy kind of implosion, causing fusion to occur in the very centre. The peppercorn “pops”.

2) The experimenters input 2.05 megajoules of energy to the target, and the result was 3.15 megajoules of fusion energy output – that is over 50% more energy than was put in (for a net gain of 1.1 megajoules). This suggests that the fusion reaction inside the pellet may have triggered other fusion reactions.

How much energy is that? Well, a typical household uses about 100,000 megajoules of energy per year, or an average of 273 megajoules per day.  So 1.1 megajoules is not much.  But it is greater than the input energy.

The Tokamak project now under construction in France for the ITER project, using magnetic confinement, is hoping to have a net energy gain factorof 10 or more (i.e. 10 times as much energy output as energy input).

Earlier this year, in February 2022, the UK JET laboratory announced thatthey had managed to have a fusion reaction last for five seconds. Thereaction produced 59 megajoules of energy, but without a net gain in energy.

3) Most of the news stories about this event state, erroneously, that fusionreactors will not produce any radioactive wastes. This is untrue. 
It is true that fusion reactors will not produce high-level; nuclear waste(irradated nuclear fuel), but It is expected that fusion reactors will release an enormous amount of tritium (radioactive hydrogen) to the environment— far more than is currently released by CANDU reactors, which in turn release 30 to 100 times more tritium than light water fission reactors. 

Moreover, because of neutron irradiation, the structural materials in a fusion reactor will beome very radioactive. The decommissioning wastes will remain dangerously radioactive for hundreds of thousands of years.

4) Many experts believe it will take at least 20-30 years to have a prototype fusion reactor in operation, even if things go quite well, and more decades will be required to scale it up to a commercial level.  Thus fusion energy will be largely irrelevant to the climate emergency we are now facing as all of the critical decision points will have passed before fusion is available. 

And, of course, there are no guarantees even then. As one commentator sardonically remarked, fusion energy is 20 years away,it always has been, and perhaps it always will be.