Proton-Boron fusion feasibility

[Melbourne Guy]

TL;DR Summary

I've seen HB11 previously and Avalanche Energy more recently pronounce proton-boron fusion as the alternative to current designs and was wondering if it is feasible?

A PF search results in some discussion of proton-boron fusion, and from those posts, it seems that cross-section issues limit the likelihood of this type of fusion device. Now, Avalanche Energy (https://www.avalanche.energy/index.html) is claiming a design that is backpack sized and capable of generating 5kWe. Note, they have not built anything and their website focuses more on rapid prototyping than the physics the underpin their idea.

Quite apart from my surprised for fusion that does not occur at Sun-like temperatures and pressures, I can't figure out how they generate electricity with their design.

Any thoughts on the feasibility of this concept.

 

[Astronuc]

I have trouble accessing the site.

Some basics on p+B11 fusion from Tri Alpha Energy (TAE): https://www.physics.uci.edu/sites/p...P20-FRC-reactor-Rostoker-08-18-2015-final.pdf

Optimum ion temperature is in the range 200-400 keV [which is about 2.3E9 to 4.6E9 K]

Without ash control: C_He ~ 70-80% resulting in a very low Q
It takes about 100 s to build up ash
High Q requires very efficient ash control
Required ash concentration < 5%

Slide 27 gives some idea of energy conversion.

80% of fusion energy goes to the side wall in form of x-rays (~150keV). Converted in electricity by a thermal cycle (50% efficiency)

Normally, the X-rays or Bremsstrahlung radiation would be considered energy losses (which they are from the plasma), but they produce thermal energy (heat) which could be transferred to a typical thermodynamic cycle to convert to mechanical energy (turbine, or thermoelectric), but that means an inefficient conversion process.

Convective energy loss into expanders (20% of fusion power) can be converted electrostatically in expanders

I believe they imply 'direct conversion' in which positive ions and electrons are separated, and the electrons flow through the a conductor producing DC.

Apparently, a couple of veterans from Blue Origin created the company.
https://www.geekwire.com/2022/blue-...lution-to-massive-challenge-of-fusion-energy/

As Avalanche Energy founders https://www.linkedin.com/in/robin-langtry-94899195/ and https://www.linkedin.com/in/brian-riordan-a7883b11/ have been grinding through the development of their fusion technology, they keep expecting to hit a wall.

The team is taking a less conventional approach to fusion energy, building a small-scale solution and foregoing the outrageous temperatures and ultra powerful magnets required by other systems. The simpler, seemingly elegant approach has left them wondering if it’s possible that no one else has developed or patented the design — or done the research showing it won’t work.

The wall, so far, has not materialized. But positive developments have. The startup has raised a $5 million seed round, secured a Patent Cooperation Treaty (PCT) International Patent, and recently emerged from stealth mode. A few weeks ago, Langtry and Riordan generated their first neutrons via fusion.

Later in the article

While researching the field, Langtry came across a graduate thesis from a Lockheed Martin researcher named https://www.linkedin.com/in/tom-mcguire-b644ab82/. It included open source code for simulations for an electrostatic fusion reactor. The idea became the seed for Avalanche Energy’s technology.

A strategy for fusion​

The startup is building its fusion generator prototype out of a mix of off-the-shelf and custom-made parts.

They’re using a modified Knight trap, a type of orbiting ion trap, as the core of the reactor and electrostatic source for high-energy, ion confinement over long periods of time. They created ion guns to fire deuterium ions — a heavy form of hydrogen — into the ion trap. A high voltage generator creates conditions in the reactor that produce the plasma in which the ions can orbit, collide, fuse and release energy.

The team has generated energy in the form of high speed neutrons, and will be adding magnets to the system to create a higher density reactor that produces more energy. They also need to set up the means for transforming the heat energy that’s produced into electrical energy.

Sound likes Avalanche Energy is considering the same approach as TAE.

One other point mentioned in the TAE presentation regards neutron production. The p-B11 is considered aneutronic, which it is, however, the product of the reaction, 3α, or the ash introduces the potential for a side reaction, α + ¹¹B => ¹⁴N + n, which is the source of neutrons in the system. Hence, the need to minimize the ash or concentration of α in the plasma.

Edit/update: Dr. Nat Fisch, a professor of astrophysical sciences at Princeton University, is the principal investigator of a new project looking at p+B11 fusion.
https://www.princeton.edu/news/2022...ng-unlikely-fantastic-clean-energy-technology

 

[Melbourne Guy]

Thanks @Astronuc, I had hoped for an informed response, but yours is above and beyond