Hitachi, Ltd.

Tsugio Iwama

Yasumasa Tamai

Yoshio Yada

A water sealing device suitable for use when a control rod drive housing welded to a stub tube and extends through a wall of a reactor pressure vessel is replaced, singly or with the stub tube, by a new one, including a sealing cylinder temporarily inserted in a control rod guide tube opening for providing a cylindrical space in which the control rod drive housing is located to shut out water in a core from the vicinity of the control rod drive housing. The sealing cylinder has a centering mechanism including a tester support portion located on an inner peripheral surface of the sealing cylinder for supporting an alignment tester for testing the alignment of centering targets mounted on upper and lower end portions of the control rod drive housing, and a tapered centering portion mounted on an outer peripheral surface of the sealing cylinder and brought into contact with a wall of the control rod guide tube opening when the sealing cylindr is temporarily inserted therein, to mount the sealing cylinder concentrically in the control rod guide tube opening through the tapered centering portion. The sealing cylinder also has a multiple seal located at a lower end portion of the sealing cylinder to allow the sealing cylinder to be brought into sealing contact with an inner wall surface of the reactor pressure vessel. Compressed air is introduced into a space in the multiple seal through the sealing cylinder.

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Mito, Japan

Tsugio Iwama