A radiation dose above the maximum permissible limit is very dangerous for human being. In radiation shielding, absorbent materials' properties must be well known. Heavyweight concrete is the most widely used in the world for this aim. The aggregate component of concrete plays an important role in improving concrete properties and this is effect of shielding properties of concrete. The thickness of any given material where 50% of the incident energy has been attenuated is known as the half-value layer. The half-value layer is expressed in units of distance (mm or cm). Like the attenuation coefficient, it is photon energy dependent. Increase of the penetrating energy of a stream of photons will result in an increase in a material's half-value layer. In this study, half-value layer thickness of concrete containing limonite, siderite and barite at different ratios was investigated; for this purpose measurements have been obtained by a collimated beam of gamma ray from sources 60 Co. The total linear attenuation coefficient (µ), half-value layer thickness is evaluated in this study.

Half value layer (HVL) is the most frequently used quantitative factor for describing both the penetrating ability of specific radiations and the penetration through specific objects. The half value layers (HVL) and tenth value layers (TVL) are defined as the thickness of a shield or an absorber that reduces the radiation level by a factor of one-half and one tenth of the initial level, respectively. The concepts of HVL and TVL are widely used in shielding design. They are photon energy dependent, like the attenuation coefficient. HVL and TVL values provide useful information about the penetration of a specific radiation in a specific material. In this study, TVL and HVL thickness are calculated for concretes with different densities. For this purpose five types of concrete with different density ranges were selected, with densities between 600-1500 kg/m 3 , called lightweight concrete, 1400-2000 kg/m 3 , called semi lightweight concrete, 2000-2500 kg/m 3 called ordinary concrete, 2500-3000 kg/m 3 , semi heavyweight concrete and 3000-4000 kg/m 3 called heavyweight concrete, respectively. For evaluated TVL and HVL thicknesses, the linear attenuation coefficients µ, were determined from measurements, using a collimated beam of gamma rays from a Cobalt-60 source.

Boralyn (Al/B4C) composite material is produced chiey of boron carbide and aluminum. Boron Carbide is an important material for the nuclear industry due to high neutron absorption cross-section. This composite is used as shielding materials to absorb neutrons in the nuclear reactors and control road materials. In this study we investigated Al/B4C composites against gamma radiation. For that purpose, 5 wt.%, 10 wt.%, 15 wt.% and 20 wt.% reinforcement content were investigated. Cs-137 gamma radioisotope source which has 662 keV gamma energy photons were used. For each material, linear and mass attenuation coecients were calculated. Theoretical mass attenuation coecients were calculated from XCOM computer code. The theoretical results were compared with experimental results. The results were showed that increasing the amount of Boron Carbide compound content of boralyn composite material decrease the linear and mass attenuation coecient of materials

In this study, boralyn (boron carbide-aluminum metal matrix composite material -Al/B4C) composite materials were investigated on shielding effect against gamma and neutron radiations. The samples were prepared as 5 wt%, 10 wt%, 15 wt%, and 20 wt% reinforcement content and for each content of material has composed in five different average particle sized (3 µm, 53 µm, 113 µm, 200 µm, and 500 µm). Linear and mass attenuation coefficients were calculated experimentally for each composite material against Cs-137 gamma source. Theoretical mass attenuation coefficients of material were calculated by using XCOM computer code. Then the theoretical results were compared with experimental results. Then, macroscopic cross-section values were calculated experimentally for each composite material against Pu-Be neutron source. As the conclusion of the study, it could be understood that in spite of decrease of the attenuation coefficient against gamma radiation, the adding materials give rise to increase the shielding ability of material against neutron radiation.

The density of the concrete is important parameter for dierent properties. Using dierent types and rates of aggregates cause dierent densities of the concretes. Radiation shielding properties can be varied with the density and it is important to obtain optimum density for this purpose. In this study radiation attenuation coecients were measured by comparison of ve dierent densities of concrete that called lightweight, semi-lightweight, ordinary and semi-heavyweight and heavyweight. For this purpose concretes were produced with suitable aggregate in laboratory conditions and determined some physical and mechanical properties. The total linear attenuation coecient measurements have been obtained by a collimated beam of gamma ray from sources 60 Co.