The MCNP5-beta code was used to calculate the reaction rate and the neutron energy response matrix of a neutron spectrometry consisting of a Polyethylene sphere with variable diameter and BF3 detector, using point and disk neutron sources, the reacti
on rate and the response matrix of disk neutron source shows higher values than those obtained for point neutron source in addition the response with disk neutron source at the energy range shows a maximum value for sphere of 10 inch diameter where the response with point neutron source stile increasing in this condition .The results obtained in this work for the disk neutron source agreed well with published results.
