Heat insulator of reactor pressure vessel and support structure therefor

A support bed is incorporated in a heat insulator of a reactor pressure vessel and they are disposed integrally. Then, space for installation and space for storing them after removal can be reduced to improve operation efficiency thereby enabling to reduce exposure dose along with operations. The heat insulator comprises inner plates and outer plates for covering the circumference of the pressure vessel, reinforcing members for supporting the gap between the inner and the outer plates and a heat insulation material filled between the frame of the inner and the outer plates. Then, the gaps are greatly reduced and heat insulation performance can be improved compared with a case of connecting heat insulators by rivets. In addition, a heat insulator at the upper lid is supported on the inner side of a container, and when the container is opened upon periodical inspection, the heat insulator can be removed together with the lid. The heat insulators at portions where there is no need to detect upon periodical inspection are fixed, and heat insulators at portions which requires detection are made operable/closable by hinges thereby enabling to further facilitate operation and reduce radiation exposure. (N.H.)