External shield structure for reactor container equipment and its construction method

Object: To enhance the safety of the external shield structure for a reactor container by providing a hemi-spherical shell dome on top of a cylindrical barrel section such that the thickness of the dome progressively decreases from the edge portion toward the apex. Structure: A hemi-spherical shell dome is provided on top of a cylindrical barrel section such that its thickness decreases from its edge toward its apex. Since the thickness of the hemi-spherical shell dome is small at the apex where the intensity of the incident radiation radiated into the atmosphere is low, and becomes progressively greater toward the edge where the intensity is high, it is possible to obtain a uniform radiation shield function over the entire region of the shell dome, thus enhancing the safety of the external shield structure of the reactor container equipment. (Moriyama, K.)