Science desk
< November 30	<< Nov \| December \| Jan >>	December 2 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is a transcluded archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

December 1

Fusion power critics

I've stumbled upon a few freak Russian critics in the internet who still allege that fusion power is principally impossible. Perhaps the most notorious seems to be Soviet-era physicist Igor Ostretsov, who published an article in a Russian scientific journal, "On the Lawson Criterion in Thermonuclear Research". Since Ostretsov's criticism is too technical for me, I started to wonder how much weight does it carry, if any. Ostretsov writes in particular:

"It is perfectly clear to every competent physicist that thermonuclear plasma, i.e. plasma at temperatures at which a thermonuclear reaction occurs, cannot be transparent. At thermonuclear temperatures, most of the energy is concentrated in radiation. In the article, I cited Zeldovich on this subject: “In complete thermal equilibrium, a significant portion of the energy is converted into radiation; this circumstance limits the equilibrium average energy of charged particles to a threshold of 5–15 keV, which is completely insufficient for a fast nuclear reaction. A slow nuclear reaction of light elements at an average energy of about 10 keV is practically impossible because the removal of energy by radiation during a slow reaction will lead to a rapid drop in temperature and a complete cessation of the reaction.” If the engineers of thermonuclear fusion in magnetic traps "secretly" assume not a thermonuclear reaction, but the synthesis of hydrogen isotopes in high-energy beams, then this is how the problem should be formulated and consider its "efficiency" as extremely ineffective. The Lawson criterion has nothing to do with that problem, since it was obtained for the Maxwellian distribution of particles by velocity, which is shown in my article".

In a letter to physicist Valery Rubakov Ostretsov further asserts that

1. The Lawson criterion was obtained for the Maxwellian distribution of particles by velocity, which is established as a result of dissipative processes (collisions). 2. As shown in my article, the particle velocity distribution function in magnetic "thermonuclear" traps is determined only by external constant and variable fields, and therefore is not Maxwellian. Due to points 1 and 2, the Lawson criterion has no relation to modern "thermonuclear" research.

Ostretsov also claims that the "during thermonuclear fusion reactions, high-energy neutrons constantly fly into the inner walls of tokamak" and "it's difficult to withstand such bombardment, while a thermonuclear reactor must operate for many years". Is anything of it true? Brandmeister^talk 16:57, 1 December 2024 (UTC)[reply]

Check who cites the article and see what they say. Abductive (reasoning) 19:23, 1 December 2024 (UTC)[reply]

There is an article about him in Russian Wikipedia. Based on it, he looks like some kind of freak. So, I think that his opinions can be safely ignored. Ruslik_Zero 20:40, 1 December 2024 (UTC)[reply]

Plasma confinement is a primary issue in the design of fusion reactors. If the plasma is insufficiently confined, which could happen in a badly designed reactor, but also due to a malfunction, the inner walls will briefly be bombarded by high-energy neutrons. But insufficient confinement also means that the fusion process stops. Of course there will always be some stray neutrons, however excellent the confinement may be. Whether the damage they inflict significantly limits the lifetime of a reactor cannot be predicted without a detailed study of the specific design of a given reactor, but this is not an issue that the designers are somehow unaware of. --Lambiam 15:27, 3 December 2024 (UTC)[reply]

Neutrons, being electrically neutral particles, are not confined by magnetic field. They will just freely leave the reactor's volume. So, 17.6 MeV neutrons will constantly bombard the walls of the reactor. This is a serious problem but it is thought to be solvable. Ruslik_Zero 20:28, 4 December 2024 (UTC)[reply]

And something else that has to put up with neutrons for years-to-decades: fission reactors. And particle accelerators. Neutron embrittlement is a known problem, but it's an "engineering problem" kind of thing: we have ways to build things that have acceptable tolerances to certain amounts of it. It's just a question of how feasible it is. At least with the neutron stuff he's actually answering a different question: "how feasible is X", not, "is X physically possible in this universe or is it impossible". Very hard: designing and building a rocketship to Mars and getting it there intact. Impossible: eating the Sun. --Slowking Man (talk) 04:34, 12 December 2024 (UTC)[reply]