We are trying to estimate the flux transmitted across a plane for 4.5 MeV neutron for a geometry as described in the input file attached. The calculated flux (neutrons/ unit area / particle) are different when the diameter of the plane is 20 cm than when the diameter of the plane is 2 cm., the remaining geometry being same for both the cases. The plot is attached. Please suggest where it is going wrong.
Madam,
The difference in the neutron flux is due to the different solid angle subtended by the area w.r.t. (Reg1b-> Reg1C) to the isotropic neutron source. If you take vacuum instead of SS316LN, the values obtained for 20 cm diameter is 2.844E-03 n/cm2/pr, whereas for 2 cm diameter, the flux values are 2.366E-02. I hope this helps.
