Reactor coolant pump having double dam seal with self-contained

Abstract

A double dam seal in a reactor coolant pump includes an internal mechanism in the seal to pressurize its annulus. In one form, the mechanism is an inclined flow passage incorporated in the rotating runner of the seal having an outlet in communication with the seal annulus and an inlet in communication with reactor coolant water flow within the pump housing and being located on a smaller radius of rotation that the passage outlet. Rotation of the runner causes rotational movement of the passage and any water therein, turning the passage and rotating runner into a centrifugal pump, causing a pressure differential along the passage due to centrifugal effects, and feeding water via the passage outlet to the seal annulus at a pressure above that at the passage inlet. In another form, the mechanism is a tube projecting at an angle from the rotating runner, or a recessed scoop defined in the runner at an angle to, and communicating with a passage having an inlet and outlet at generally the same radius of rotation. The tube or scoop are also at generally the same radius of rotation but extend upstream of the passage inlet. Rotational movement of the tube or scoop with the rotating runner through the reactor coolant water in the seal housing develops a pressure higher at the passage inlet than outlet which, in turn, is supplied by the passage to the double dam seal annulus.