Patent ID: 6888909

Claim:
A reactor pressure vessel (RPV) for containing nuclear fuel assemblies in coolant water, comprising: a vessel body having an internal support ledge; a removable top head having a flange and an inner surface defining a head cavity; a core barrel assembly having a flange supported on the internal support ledge for supporting the fuel assemblies, the core barrel assembly flange having holes extending between a lower flange surface and an upper flange surface, each hole disposed inwardly of the internal support ledge, each hole having a cross-sectional area; and an upper support plate having a flange with a lower flange surface and an upper flange surface and a periphery extending between the lower flange surface and the upper flange surface, the lower surface of the upper support plate flange disposed above and spaced from the upper surface of the core barrel assembly flange, the lower surface of the upper support plate flange and the upper surface of the core barrel assembly flange defining an inter-flange cavity, the periphery of the upper support plate flange and the vessel body defining a coolant water leak way in flow communication with the inter-flange cavity, the upper support plate flange having holes extending between its lower surface and its upper surface and aligned with the holes in the core barrel assembly, the holes in the upper support plate flange disposed in coolant flow communication with the holes in the core barrel assembly flange and with the inter-flange cavity and the coolant water leak way, the holes in the upper support plate flange disposed inwardly of the removable top head flange and opening to the head cavity for discharging coolant water along the inner surface of the removable top head, each upper support plate flange hole having a cross-sectional area; wherein the cross-sectional area of the core barrel assembly flange hole is smaller than the cross-sectional area of the aligned upper support plate flange hole for controlling leakage of coolant water in the head cavity around the periphery of the upper support plate flange and into the inter-flange cavity and induction of the leaked coolant water by the coolant water flowing into the holes in the upper support plate flange.