Gamma-ray densitometry or nucleonic gauges have been widely used in industries to improve the quality of products, optimize processes and save energy and materials. Compared with common time-consuming and expensive chemical analyses, the proposed method is relatively fast and more reliable. Density measurement is normally based on the absorption of gamma radiation as it passes through the process material. The absorption which is proportional to the changes in material density indicates product density as the measuring path is held constant. In this study, a number of Monte Carlo simulations have been performed using the MCNP-4C code to optimize the arrangement of gamma densitometer. The dimensions of the proposed system have been chosen to coincide with the industrial specimen of gamma densitometer. The geometry of source to detector in different angles was investigated and optimized angles were chosen. The simulation as well as experimentally measurements has been performed for 4 different fluids including water, gasoline and diesel engine oil used with iron and PVC pipes of 4 inches diameter. The gamma source and detector have been a ¹³⁷Cs and NaI(Tl) scintillation detector. Our experiments and simulations results show that the transmission mode present, better results than the scattering one in densitometer. The single detector response of the detector located at 180

Radioactive ray safeguard is a physical impediment which is placed between radioactive source and the protected object in order to decrease the amount of rays' radiation in the protected area. Different materials such as lead, iron, graphite, water, poly ethylene, concrete, or rubber can be used for protection against nuclear radiations. In safeguard's common designing, two types of Gama and Neutron radiations are usually considered. The weakening amount of Gama radiations is proportional to the mass and atomic number of the safeguard's material. Covering Neutron source varies with regard to the source power and its application. However, what is always true is having the least dose with the least dimensions outside the safeguard. The dose of the safeguard's outside partition is resulted from quick, slow and thermal neutrons, and also from the source's Gammas and secondary Gammas. Neutrons use retarding and neutron-absorbing materials in order to reduce the dose. Due to the weak mechanical characteristics of the pure elastic composites, fillers are used to strengthen and improve their characteristics. Strengthening the elastic material is often defined through increasing the characteristics such as hardness, module, refraction energy, solidity, tear resistance, tensile solidity, lassitude resistance, abrasion resistance. In this paper, rubber shielding materials with boron carbide and tungsten as impurities have been fabricated. The optimum boron carbide contents (5% weight percent) have been evaluated using the Monte Carlo code, MCNP. The gamma attenuation coefficients for different boron carbide and tungsten contents have been measured for a number of rubber shields with dimensions of 1