Ferreting out the truth about fusion: Interview with Bob Rosner
By Dan Drollette Jr | November 12, 2024
A researcher in the interior of the magnetic fusion experiment known as Alcator C-Mod at MIT. The interior of the donut-shaped device confines plasma hotter than the interior of the sun, using high magnetic fields. Image courtesy of Bob Mumgaard / Plasma Science and Fusion Center, MIT.
Ferreting out the truth about fusion: Interview with Bob Rosner
By Dan Drollette Jr | November 12, 2024
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Keywords: ITER, NIF, Nuclear Fusion Energy, alternative energy, climate change, fossil fuels, magnetic fusion, plasma, stellarator, tokamak
Topics: Climate Change, Nuclear Energy, Nuclear Risk, Nuclear Weapons
Dan Drollette Jr
Dan Drollette Jr is the executive editor of the Bulletin of the Atomic Scientists. He is a science writer/editor and foreign correspondent... Read More
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Theoretical physicist Robert Rodney argued for the importance of NIF. He stated that the U.S. Department of Energy (DOE) and the Lawrence Livermore National Laboratory (LLNL), where NIF is located, clearly state its primary purpose. Typically they mention NIF is an essential component in the Stockpile Stewardship Program, or that it is part of the nation’s nuclear deterrent, in an off-hand way. They are masters at obscuring the fact that it has always been primarily funded as a thermonuclear weapon (H-bomb) research tool. The frequently cited December 5, 2022, ‘breakeven’ laser shot never mentions that a weapons related target was… Read more »
Neutronic fusion does not make sense from a system point of view. If you are going to boil water with neutrons to make electricity you might as well put your money in developing advanced nuclear reactors such as the liquid salt Thorium reactor.
If fusion is to be practical and clean for generating electricity you need aneutronic fusion to power you system. That is where the research dollars should be going. Note that NIF does what it is supposed to do, that is simulate nuclear weapons. No problem with neutrons in that case you want them.
Well, to increase the efficiency of these reactions which have barely reached a Q of 1 you might take the heat generated here and turn it to electricity which could then spawn many LENR reactions whose energy could be fed back into your fusion cycle. This is pure speculation but has not been tried yet and I am the only one proposing this. LENR on its own has a 100 year history and now is on a firm theoretical basis with Widom and Larsens 2006 article and is a cleaner more efficient nuclear reaction. As far as stellar evolution stars… Read more »
Note that LENR is a rebranding of the earlier ‘cold fusion’ which had to be dropped due to the embarrassing failures to reproduce many of the earlier experiments. Almost none of the dozens of experimental nuclear fusion energy experimental machines have generated any significant quantity of fusion reactions since they never were intended to use the 50-50 mix of deuterium and radioactive tritium. What most people have heard is promotional snow jobs from the fusion insiders. The Q value that you are referring to is Q-plasma which only involves the energy coupled into the plasma to heat it. Typically it… Read more »
The most energetic neutrons are approximately 2 megavolts (MeV) in fission reactors The high energy tail of the fission neutron spectrum goes to energies several times higher than that. What is significant about fission is that only 3% of the total energy comes off as neutrons, vs. 80% in DT fusion, and also that DT neutrons are above threshold for (n,2n) reactions (and have much higher cross section for (n,p) and (n,alpha) reactions) in many materials. The neutrons from DD fusion (if DT can be suppressed) would be even lower in maximum energy than fission neutrons. This is a point… Read more »
The rumored 10 MJ laser in China was probably started and nurtured by US interests, who want a larger facility than NIF. However, NIF’s ultimate potential is not so far from 10 MJ. Today’s NIF can actually deliver at least 4 MJ, but at a wavelength of 1.05 micron, which causes instabilities in the hohlraum filling gas. The “final optics assembly” in the beamlines frequency-triples the laser light, which reduces the wavelength to 0.35 micron, where instability problems are less severe. However, this frequency conversion results in an energy loss of a factor of 2. The NIF has… Read more »
Thank you for pointing out the upgrade efforts for the NIF laser banks and the specific wavelengths involved in their shots. The billions of dollars of expenditures on this project are driven by the fact that NIF’s primary purpose has always been as a thermonuclear weapon (H-bomb) research tool. The broadly announced ‘breakeven’ shot, conducted on December 5, 2022, took about a week to prepare while the fusion reaction propagation lasted for approximately 0.000,000,000,08 second before the ‘hotspot’ disassembled. The technology has many orders of magnitude to go to reach anything close to ten shots per second. In that frequently… Read more »
The 4% burn-up of fusion fuel (D and T) achieved by NIF is actually a significant achievement. A practical ICF power plant would have a burn-up of 35 to 50%, a factor of 10 above NIF’s value, but NIF’s energy upgrade now under way will eat into that gap. Compare that with the tokamak situation: TFTR and JET are the only magnetic confinement devices to have used tritium, and the tritium burn-up in their best shots was only 0.01%— 400 times smaller than in the NIF ! A practical MCF power plant needs a burn-up of 4 or 5%, a factor of… Read more »