Aneutronic Fusion Candidates
(0) Comments“A” means “without”. Therefore “a-neutronic” is “without neutrons”. Aneutronic fusion means fusion that does not seek to produce neutrons as a by-product.
From Wikipedia:
Aneutronic fusion is any form of fusion power where neutrons carry no more than 1% of the total released energy. The most-studied fusion reactions release up to 80% of their energy in neutrons. Successful aneutronic fusion would greatly reduce problems associated with neutron radiation such as ionizing damage, neutron activation, and requirements for biological shielding, remote handling, and safety. Some proponents also see a potential for dramatic cost reductions by converting energy directly to electricity.
No (well, OK, negligible) neutrons means no radioactivity, no nuclear waste and no weapons capability. Nuclear energy without nuclear waste or nuclear weapons! This is great!
Once mankind discovers how to create net energy from an aneutronic fusion reaction, we will have solved the energy problem and the pollution problem in one stroke. So what’s the holdup?
The conditions required to harness aneutronic fusion are much more extreme than those required for the conventional deuterium–tritium (DT) fuel cycle.
Ah. The catch. The hurdle. The task. Let’s get to know a bit more about our manxome foe.
Aneutronic Fusion Fuels
Apparently there are a lot of ways we could go about this. There are a lot of things to fuse together. The stuff you fuse is your fuel. Fusion fuels are the lighter elements (to understand why, you might want to visit the iron valley - post pending). Typical fuels considered are light atomic nuclei like hydrogen, deuterium, tritium, helium, lithium, beryllium, boron, and their various isotopes.
Aneutronic fusion, which seeks low neutron radiation hazards, uses isotopes like hydrogen-1, helium-3, lithium-6, lithium-7 and boron-11 (see these and other candidates.
| 1H + 2 6Li → | 4He + (3He + 6Li) → 3 4He + 1H | + 20.9 MeV( 153 TJ/kg ≈ 42 GWh/kg) |
| 1H + 7Li → | 2 4He | + 17.2 MeV ( 204 TJ/kg ≈ 56 GWh/kg) |
| 3He + 3He → | 4He + 2 1H | + 12.9 MeV ( 205 TJ/kg ≈ 57 GWh/kg) |
| 1H + 11B → | 3 4He | + 8.7 MeV ( 66 TJ/kg ≈ 18 GWh/kg) |
Boron and helium-3 are special aneutronic fuels, because their primary reaction produces less than 0.1% of the total energy as fast neutrons, meaning that a minimum of radiation shielding is required, and the kinetic energy from fusion products is directly convertible into electricity with a high efficiency, more than 95%, as will be further described.
Boron is available in the Earth’s crust and helium-3 is available in the lunar regolith, both are relatively plentiful if compared to tritium.
Hydrogen and Boron eleven are the ones used by Focus Fusion. As you see from the equation below - no neutrons are produced.
p + B11 -> 3 He4 + 8.7 MeV
Aneutronic Fusion Poster
This poster has “Aneutronic Fusion” and the “arms raised up peace symbol” on one side. On the reverse side, we have a brief explanation of aneutronic fusion vs. DT fusion vs. fission. There’s a lot of information to cram in if you want to understand the aneutronic fusion concept.
Download the pdf here. Thumbnails of the front and back:
Giving Thanks, 2009
How Hard Is It?
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