Secondary protection barrier( for scattered photons and leakage radiation), depending on ratio of scattering to incident radiation scattering field size, exposure rate on scatterer....
Distance between "source and scatterer" and "scatterer and objective place" are related to allowable value as well as occupancy factor and others.
Eventually, I want to find the required barrier thickness. Usually we would find K or B, attenuation factor) first, then we can use some table or figure to find the corresponding required wall thickness.
Beta ray shielding:
Gotta consider both electrons and bremsstrahlung radiation. To calculate the bremsstrahlung part, we first find the fraction of energy emitted as bremsstrahlung. And then to find the required thickness of wall.
For fast neutron.
Use table 9.5, we could find the relation of neutron energy and neutron flux that cause a 0.01 Sv/h.
Once we know the attenuation cross section, we can know the flux distribution of neutron in the wall. At the end point of wall, the flux of neutron should equal the required value. This is, we could find the required wall thickness.
For thermal neutron.
Gotta consider gamma capture reaction. Usually, we assume a uniformly distributed gamma source. Then we have equation to fine the dose rate on the surface of the sphere.
So, we have dose rate from fast and thermal neutrons and gamma rays. One way to reduce gamma ray radiation, we could add some lower energy emitter like boron(0,48Mev).