dodecahedron

[MSimon]

Concrete is preferred due to costs.

For gammas the deal is: total mass. So you look at cost per ton installed.

[MSimon]

Of course that assumes concrete.

If the neutrons get thermalized with a water jacket of 6" or 8" and then absorbed with elemental boron or a borax sludge it could be thinner.

The NRC will still want to keep an eye on you.

Would that elemental boron or borax sludge by Boron 10 or 11? What does Boron do when it absorbs neutrons? Maybe the shielding could be made of "depleted Boron 10" leftover from enriching the Boron to make the Boron 11 fuel.

Borax sludge would probably be the cheapest installed. B10 is what does the absorbing.

[Barry Kirk]

When the B10 absorbs a neutron, does it become B11?

Although it sounds like very few neutrons will be generated compared to the amount of B11 consumed.

[drmike]

The main reactions are B-10(N,0)B-11, B-10(N,A)Li-7, B-10(N, T)BE-8, B-10(N,T+A)HE-4, B-10(N,D)BE-9 and elastic scattering along with inelastic (Boron goes to high energy state and spits out a gamma and a low energy neutron). See NNDC for details (put in B-10 for the target, (N,*) for the reaction).

[MSimon]

The main reactions are B-10(N,0)B-11, B-10(N,A)Li-7, B-10(N, T)BE-8, B-10(N,T+A)HE-4, B-10(N,D)BE-9 and elastic scattering along with inelastic (Boron goes to high energy state and spits out a gamma and a low energy neutron). See NNDC for details (put in B-10 for the target, (N,*) for the reaction).

Thanks! Added to IEC Fusion Tech sidebar

[rnebel]

Colonel_Korg

The principle reaction is the alpha-11B reaction. Neutron energies are ~ 150 keV. Absorbing the neutron in boron produces a gamma, which also needs to be shielded.

[TallDave]

We've done the calculations. Neutron yield from a P-B11 Polywell machine (nonthermal) is about 1.0e12/sec. for a 100Mwe reactor. That's about 8 orders of magnitude less than a comparable D-T machine.

Cool! Thanks for sharing.