Rotary shield plug

Object: To shield Na vapor of a liquid metal coolant accommodated within the container of a fast reactor with a doublewall shield structure, thereby increasing the shielding reliability. Structure: A gap between the container wall of fast reactor container and rotary plug for closing the top opening of the reactor container is hermetically shielded at the upper end and is doubly shielded at the lower end by two shielding means. Of these shielding means, the first one projects from the container wall and is in contact with the bottom of the rotary plug, while the second shield means consists of a first annular member extending from the bottom of the rotary plug and a second annular member extending from the container wall and abutting the first annular member to define a space between the first and second annular members. Further, an inert gas circulating means is provided between a blow-in inlet positioned above the first shield means on the container wall and an exhaust outlet positioned above the space within the container wall. (Kamimura, M.)