Question

Monoenergetic neutrons are being emitted Is otropically from a point source in an infinite medium at a rate q0 neutrons/s. If the nuclei of the medium have σa, negligible σs, nuclear density N, find the number of neutron absorptions occurring per cubic centimeter per second at each point of the infinite medium.

Answer 1

For neutron interactions incident upon sheet of material, the nuclear reaction rate equation is

• : number of reactions of type x, units: [1/time/volume]
• : beam flux, units: [1/area/time]
• : microscopic cross section for reaction, units: [area] (usually barns or cm²).
• : density of atoms in the target in units of [1/volume]

we have

= q0

= + =   (approx)

= N

thus the number of neutron absorptions occurring per cubic centimeter per second ie

=   q0 * * N