The production of phosphorous after neutron irradiation on intrinsic samples was studied.All the samples were annealed at 800 oC for one hour after neutron irradiation. The purpose is that to remove defects from the irradiated samples. After Annealing etching were carried out in mixture of hydrofloric acid (HF ) and deionized water ( DI water) for removing oxide layer from the surface of samples.The samples were characterized by DC- electrical resistivity ,% reflection and secondary ion mass spectroscopy ( SIMS). DC -electrical resistivity was carried out before and after annealing . DC -electrical resistivity as measured with four -point probe method for each irradiated and un -irradiated sample. From plots we observed that resistivity of irradiated samples were lower than the un -irradiated sample. The reason is that there is N -type doping after neutron irradiation. Concentration of phosphorous was estimated by using secondary ion mass spectroscopy ( SIMS). From plots we observed that with the increase of neutron irradiation, concentration of phosphorous will increase. The result is that concentration of phosphorous depends upon strength of neutron irradiation.