Reply To: Repowering the electric utility industry

[Joeviocoe]

The X-Ray emissions are not really a waste product to be shielded against and/or discarded, but must be collected in “the onion” for over 40% of the total recoverable energy.

BSFusion wrote:

So, to be clear, would a pB11 FF reactor definitely need shielding to be around humans, or not?

For a p-11B FF reactor, in addition to neutrons, large quantities of hard X-rays will be produced by bremsstrahlung, and 4, 12, and 16 MeV gamma rays will be produced by the fusion reaction. Shielding from gamma rays requires large amounts of mass, in contrast to alpha particles which can be blocked by paper or skin, and beta particles which can be shielded by foil. Gamma rays are better absorbed by materials with high atomic numbers and high density, although neither effect is important compared to the total mass per area in the path of the gamma ray. For this reason, a lead shield is only modestly better (20-30% better) as a gamma shield, than an equal mass of another shielding material such as aluminium, concrete, water or soil; lead’s major advantage is not in lower weight, but rather its compactness due to its higher density. Protective clothing, goggles and respirators can protect from internal contact with or ingestion of alpha or beta particles, but provide no protection from gamma radiation from external sources.

From what I understand, gamma emissions are extremely rare in pB11 reactions in a Dense Plasma Focus. For a gamma to be produced, the intermediate reaction of the Carbon-12 breaking up into three He-4 (alpha particles), never occurs. And the Carbon-12 releases it’s extra energy as an energetic photon (gamma ray).

Lerner wrote: That reaction occurs only at energies above 7Mev and even at 14 Mev, is about a million times less likely than the tri-alpha one is at 600 keV.

https://focusfusion.org/index.php/forums/viewthread/693/

So, no real shielding is needed for gamma rays either.
Eric, what shielding have you calculated will be needed for a 5MW reactor?