| 摘要 |
A closure insert assembly (10) for a control rod drive mechanism that has incorporated therein a vent valve arrangement which permits the release of air trapped in the nuclear reactor during the filling of the primary coolant system therein and allows the entrance of air into the reactor for the draining of same. To accomplish this, the vent valve is of the ball type which engages two oppositely disposed conical ball seats (44, 70), one of which is allowed to move laterally with respect to the other, causing the ball (66) and ball seats (44, 70) to be "self-centering" and resulting in a uniform compressive force being applied over minor circumferences on the ball (66). The use of conical ball seats (44, 70), one of which is laterally movable, also permits the axes of the conical ball seats (44, 70) to be non-parallel and/or non-concentric without hindering the operation and effectiveness of the vent valve.
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