THERMAL BARRIER FOR REACTOR COOLANT PUMP

摘要

A thermal barrier for a nuclear reactor coolant pump includes a stack of pancake cooling coils encircling the pump shaft where it enters the pump chamber. This stack of coiling coils has an irregular peripheral surface formed by axially extending, diametrically opposed, inlet and outlet tubes which are circumferentially indexed for each pancake coil. The inner surface of a cylindrical cover has a complimentary inner peripheral surface formed by two sets of diametrically opposed cascaded steps so that the volume of the annulus between the coil stack and cover is minimized to reduce stratification of cooling water injected into the cover. A collar around the pump shaft at the opening in the end wall of the cover extends axially into the coil stack to prevent vortices produced by the spinning shaft from flowing across the end wall of the cover, while circumferentially spaced holes in the collar prevent significant alteration of the thermal conditions of the pancake coiling coils. An integral flange on the collar serves as a shim for the stack of coils. An external insulator includes a sleeve with a low coefficient of thermal expansion shrink fit over a groove in the outer surface of the cylindrical cover to form an annular chamber which is divided by a number of nested cans into a plurality of concentric sections each containing stagnant reactor coolant.