What To Do With Those Neutrons? Part 2, Neutron Effects
Interesting citation here indicating that "[f]ew previous studies have shown measurable effects on the mechanical properties of HY-80 steel if irradiation levels are below 1x1017n/cm2." Nevertheless, it it would be useful to see what kind of radioactive changes the neutrons might induce in said steel. Using the wise-uranium.org calculator, for fast neutrons bombarding 1 kg stainless for a year, we get the following (slightly reformatted):
There's a fair number of short-lived isotopes there, which usually means you'll end up with a mess of radioactivity. I'm still working on calculating all the decay products.Neutron flux = 647.0e9 per cm2s Irradiation = 1 a; Delay = 0 h Original Reaction Activation Half- Nuclide & Decay (~>) Life Products 710.0 g Iron: Fe-54 (n,3n) -> Fe-52 (8.275 h) ~> Mn-52m (21.40 m) ~> Mn-52 (5.592 d) Fe-54 (n,p) -> Mn-54 (312.7 d) Fe-54 (n,t) -> Mn-52 (5.592 d) Fe-54 (n,A) -> Cr-51 (27.70 d) Fe-56 (n,2n) -> Fe-55 (2.700 a) Fe-56 (n,p) -> Mn-56 (2.578 h) Fe-56 (n,t) -> Mn-54 (312.7 d) Fe-57 (n,3n) -> Fe-55 (2.700 a) Fe-57 (n,p) -> Mn-57 (1.470 m) Fe-58 (n,t) -> Mn-56 (2.578 h) 190.0 g Chromium: Cr-50 (n,2n) -> Cr-49 (42.09 m) ~> V-49 (330.0 d) Cr-50 (n,t) -> V-48 (15.97 d) Cr-52 (n,2n) -> Cr-51 (27.70 d) Cr-52 (n,p) -> V-52 (3.750 m) Cr-53 (n,3n) -> Cr-51 (27.70 d) Cr-54 (n,t) -> V-52 (3.750 m) Cr-54 (n,A) -> Ti-51 (5.750 m) 100.0 g Nickel: Ni-58 (n,2n) -> Ni-57 (1.503 d) ~> Co-57 (270.9 d) Ni-58 (n,3n) -> Ni-56 (6.099 d) ~> Co-56 (78.77 d) Ni-58 (n,p) -> Co-58 (70.81 d) Ni-58 (n,t) -> Co-56 (78.77 d) Ni-58 (n,A) -> Fe-55 (2.700 a) Ni-60 (n,2n) -> Ni-59 (75.00e3 a) Ni-60 (n,p) -> Co-60 (5.271 a) Ni-60 (n,t) -> Co-58 (70.81 d) Ni-61 (n,3n) -> Ni-59 (75.00e3 a) Ni-61 (n,p) -> Co-61 (1.650 h) Ni-62 (n,t) -> Co-60 (5.271 a) Ni-62 (n,A) -> Fe-59 (44.64 d) Ni-64 (n,2n) -> Ni-63 (100.1 a)
A very cranky, opinionated look at this was on talk-polywell, but I missed it earlier.
Update 10/18: Back to our 1 GW reference case, this means radiated power from fast neutrons (just the 11B + α reaction) ends up as
7.3x1017 neutrons/s * 2.7x106 MeV/neutron * 1.602x10-19 J/eV = 316 kWM. Simon suggested that a 500 MW Polywell device would throw off 5 kW of neutrons. I'm not sure how he derives that figure, but I'll ask.
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