Shielding Effect for Gamma rays with Reinforcing Bars in Reinforced Concrete (High-energy Gamma rays)

Reinforced concrete is generally used as a shielding wall for synchrotron radiation facilities where high-energy gamma rays are generated. The shielding effect of high-energy gamma rays should vary depending on the diameter of the reinforcing bars (rebars) in the reinforced concrete. The consistency among four types of Monte Carlo radiation transport codes was confirmed through concrete calculations of 1.25 and 10 MeV gamma-ray sources and the analyses of the results of Bishop experiment. We compared the leakage neutron and gamma-ray effective dose rates from the concrete (100 cm thickness) with and without rebars for 10 to 3000 MeV gamma-ray plane sources using four types of Monte Carlo codes. The shielding effect was evaluated from the ratio (decrease ratio) of the leakage radiation dose of the reinforced concrete to that of the concrete without rebars. The decrease ratio of high-energy gamma rays by MCNP6 decreased linearly as the diameter of the rebars increased.