Least neutronic fusion chemistry so far?

[jamesr]

As far as I know you would always need neutron shielding. The small proportion of side reactions is still enough to be concerned about, while the device is operating. In nuclear safety the principle is of “As Low as Reasonably Achievable” (ALARA) or in the UK its known as “As Low as Reasonably Practicable” (ALARP). Basically means if there is something you can do to lower the dosage and risk you should do it. Any regulator would insist on it.

So the DPF device (outside the onion but inside as much else as possible) would be surrounded by a water blanket doped with boron-10, or alternatively plastic shielding tiles like Boratron. The hydrogen in the water/plastic slows down the neutrons to a low enough speed that they can be absorbed by the B-10. This absorption releases gamma rays, so outside the neutron shield you need a further small amount of lead or high density concrete gamma shield.

[opensource]

Using water and lead shielding will make applications in transportation more difficult. Lerner said the main reaction does not produce any, so do we have a list of the (side) reactions that are producing the neutrons?

[asymmetric_implosion]

The one that I am aware of is reactions of the alpha particles with Beryllium (Be). The reaction combines an alpha particle and the Be-9 to make Carbon-12 (C-12) and a neutron. The alpha+Be-9 reaction is commonly used to make small neutron sources. Common sources rely on ~4 MeV alpha particles but I believe the reaction is exothermic other than that pesky Coulomb barrier problem. Other reactions would depend upon the specific materials that make up the first wall the system and the electrodes. I know Be has come up often in the discussions of the FoFu anode. The usual data bases did not have a reaction cross section but it has to be reasonable if the reaction is used in commercial neutron sources. This reaction alone might be enough to produce a significant neutron flux. The Beryllium will not be radioactive because the product is C-12.

It’s not at all clear to me that a Be anode can survive in FoFu-1 given that significant quantities of SS304 were observed to be eroded on smaller machines by Bures et al (DOI: 10.1109/TPS.2012.2183648). That is a bigger picture issue about x-ray absorption and electrode lifetime.

Another source that could contribute is D-D. If the fuel gas is isotopically pure, this reaction should not take place. More details of the vacuum chamber and electrodes are required to address any other reactions that might produce neutrons.

[Joeviocoe]

BSFusion wrote:
No, the accronym BSF stands for Bubble-confined Sonoluminescent-laser Fusion, as spelled out in patent appl#: 12/803901, not Bubble SonoFusion. The concepts overlap, but there are major differences. If I changed the name to Matter-confined Laser Fusion (MLF) would that eliminate your objection?

I will address this on your thread. So we can get off his.
https://focusfusion.org/index.php/forums/viewthread/378/

opensource wrote: Using water and lead shielding will make applications in transportation more difficult. Lerner said the main reaction does not produce any, so do we have a list of the (side) reactions that are producing the neutrons?

11B + α → 14N + n + 157 keV
and
11B + p → 11C + n − 2.8 MeV

Are the two neutron producing side reactions that I am aware of. The first one is by far the most prominent. The second one should produce a neutron with very very low energy.

Thanks James for the clarification. Mobile operations will indeed be difficult if heavy gamma shielding is needed. But submarines and ships can handle it since they already deal with heavy shielding for their fission reactors.

[Lerner]

Yes, the second one can probably not be avoided. That is why the generator must cool down before maintenace to allow the C11 to decay.

[opensource]

So Lerner,

The above list of reactions creating neutrons and ionizing radiation is exhaustive?

An the second one (11B + p → 11C + n − 2.8 MeV) is the only one you think can’t be avoided?

I’m focusing on the need for shielding, not byproducts that affect maintenance. To me this is a bigger issue affecting my investment in DPF research.

[zapkitty]

Joeviocoe wrote:
Thanks James for the clarification. Mobile operations will indeed be difficult if heavy gamma shielding is needed. But submarines and ships can handle it since they already deal with heavy shielding for their fission reactors.

When considering mobile uses for FF units one must take into consideration the mass and volume not only of the power system being replaced but also the mass and volume of the fuel (usually fossil) that is no longer needed. The mass and volume of fossil fuel storage is a surprisingly large portion of all current Earthside transport methods.

The most common near-term mobile uses considered for commercial FF units (given that the parameters proposed by LPP hold up) are for:

cars – too heavy

trucks – semi-sized [em]could[/em] be made to work

trains – a good fit

large watercraft – also a good match. The Navies of the world will love you forever.

large hovercraft – well… [em]I[/em] considered them 🙂 Some interesting possibilities, I think.

aircraft – high subsonic cargo transports, which is the bulk of commercial aviation, should work well if you can deal with the C11 in a crash scenario

spaceborne applications – good for surface bases and large space stations but FF launch vehicles and FF-propelled spacecraft will require a scale of vehicles and infrastructure not yet under consideration… or a very [em]interesting[/em] lack of shielding 🙂

… but you could plant crewed lunar research stations wheresoever they suited you.

[Henning]

With spacecrafts you probably only need half of the shielding to protect the crew, and let the neutrons “evaporate” up. This needs special handling on the launch site, when maintenace crew needs to service the craft.

[annodomini2]

Re: Spacecraft,

I doubt FF would be used as a power source to get on orbit. The vehicle mass would be excessive and other than superheating material for mass ejection there are currently no known propulsion systems that could use electricity and generate sufficient thrust to get a manned space vehicle off the ground. (That don’t produce excessive amounts of ionising radiation in the process).

If an FF was used as a power source on a space vehicle I would see it being used more for deep space, rather than on orbit. Shielding is less of an issue of mass in this situation as the crew will need shielding anyway.

Again on a base, on the moon for example, I would have thought burying it would be more beneficial than taking shielding with you.

[zapkitty]

Henning wrote: This needs special handling on the launch site, when maintenace crew needs to service the craft.

Nope. You’ve confused the FF unit with a fission reactor.

A fission unit is a neutron source whether it’s on or off.

An FF unit is just a pile of machinery when it’s turned off. When even an unshielded FF unit is not operating there won’t be a neutron problem for the maintenance crew to worry about.

And be advised that attempts at describing “near-term” FF-powered launchers are an interesting mental exercise but should not even be considered in a real-world context of near-term FF power plants and then ships etc etc.

[Henning]

Well, you’re right. The supposed accumulation of radioactivity after a year of operation, is somewhat of the joined a school class of forty kids (non-ukrainian, non-japanese), as Eric explains it somewhere else in the forums.

[benf]

opensource wrote: So Lerner,

The above list of reactions creating neutrons and ionizing radiation is exhaustive?

An the second one (11B + p → 11C + n − 2.8 MeV) is the only one you think can’t be avoided?

I’m focusing on the need for shielding, not byproducts that affect maintenance. To me this is a bigger issue affecting my investment in DPF research.

The subject of radiation has been debated many times in the Forum, which you can easily do a search for. The upshot is that with pb11 the DPF is going to be the cleanest burning fusion generator out there and will be producing prodigious amounts of power. All with a very compact footprint. What more do you need? What more do you think is really possible with any other design?

I think your investment dollars would be well rewarded in DPF research.

[Joeviocoe]

benf wrote:

So Lerner,

The above list of reactions creating neutrons and ionizing radiation is exhaustive?

An the second one (11B + p → 11C + n − 2.8 MeV) is the only one you think can’t be avoided?

I’m focusing on the need for shielding, not byproducts that affect maintenance. To me this is a bigger issue affecting my investment in DPF research.

The subject of radiation has been debated many times in the Forum, which you can easily do a search for. The upshot is that with pb11 the DPF is going to be the cleanest burning fusion generator out there and will be producing prodigious amounts of power. All with a very compact footprint. What more do you need? What more do you think is really possible with any other design?

I think your investment dollars would be well rewarded in DPF research.

I think what opensource may be getting at is this:
Are there any downplayed drawbacks to the DPF shielding requirements that might make DPF a much less attractive solution in the future?

Such as how Nuclear Fission Power was once regarded as silver bullet to energy needs. It produced LOTS of power in a very small reactor (compared to other power plants at the time). And the fuel was VERY abundant too. But dealing with radiation (both in the reactor and the fuel itself) proved to be more problematic than many early claims indicated. Shielding, safety systems, fuel handling, separation of water cycles, waste handling…. were all problems created due to radioactivity. And those problems made Fission power plants MUCH larger and MUCH more expensive. So now, Nuclear power makes up only 20% of the electric power in the U.S.

It is a very pertinent question to ask about the exact requirements for shielding. We have already eliminated most concerns; the fuel (decaborane is toxic but non-radioactive), no radioactive water cycles, and waste is inert helium. The only concerns left are the safety systems of High electrical power (easy) and shielding from possible radiation from side reactions.

[opensource]

Joeviocoe wrote:
I think what opensource may be getting at is this:
Are there any downplayed drawbacks to the DPF shielding requirements that might make DPF a much less attractive solution in the future?

Such as how Nuclear Fission Power was once regarded as silver bullet to energy needs. It produced LOTS of power in a very small reactor (compared to other power plants at the time). And the fuel was VERY abundant too. But dealing with radiation (both in the reactor and the fuel itself) proved to be more problematic than many early claims indicated. Shielding, safety systems, fuel handling, separation of water cycles, waste handling…. were all problems created due to radioactivity. And those problems made Fission power plants MUCH larger and MUCH more expensive. So now, Nuclear power makes up only 20% of the electric power in the U.S.

It is a very pertinent question to ask about the exact requirements for shielding. We have already eliminated most concerns; the fuel (decaborane is toxic but non-radioactive), no radioactive water cycles, and waste is inert helium. The only concerns left are the safety systems of High electrical power (easy) and shielding from possible radiation from side reactions.

Indeed, and I still get a variety of different answers on the main forum focused on the best fusion power DPF out there.
I’m trying to get an exhaustive list of the reactions that cause the theoretically safest DPF (pB11 fuel, etc) to require shielding around humans.

[asymmetric_implosion]

I agree with Joe’s comment up to point of “eliminating most concerns”. As with fission, fusion could find unexpected and unintended consequences that drive up costs. I agree that radioactive consequences are far less likely with the 11B-p reaction depending upon the choice of materials around the pinch, other concerns could crop up. I don’t have a crystal ball but I can tell you from operating PF devices and other pulse power devices that something always seems to come up that was unexpected or unintended. I admit that some unintended and unexpected things were quite wonderful while others were very disappointing. For example, high repetition rate devices tend to very loud and can shake the ground. Probably fine for a boat but on a truck it might require extra resources in excess of radiation shielding. On the upside we’ve noticed that operating at higher temperatures improves the fusion yield so increasing the repetition rate might lead to lower currents and the same fusion yield per shot.

If you are investing in this technology do it because you believe the problems can be solved. If you believe the problems are solved, I think you will be disappointed with the lack of return on investment.

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