Patent Number: 060552883
Section: abstract

A nuclear reactor vessel has a baffle-barrel assembly for supporting the fuel assemblies in its core region and guiding coolant flowing through the core region when the reactor vessel is in service. The baffle assembly includes a baffle plate fastened to a former plate by a bolt. The baffle plate has a countersunk hole extending to a smaller diameter baffle plate hole. The former plate has a bolt hole aligned with the baffle plate hole. The bolt has a head portion disposed in the countersunk hole and a shank extending from the undersurface of the head portion into the aligned bolt holes and threadedly engaged with the former plate. A hole or slot extending through or along the bolt head and externally of the shank is formed in the bolt head itself or between the bolt head and the baffle plate for flowing coolant past the undersurface of the bolt head and the crevice it forms with the baffle plate so that steam which may form under the bolt head will be readily vented, deposited particulates from stagnant coolant and precipitates from the steam will be washed from the underside of the bolt head and the adjacent crevice, and the bolt head will be cooled. Because the shank does not have an axial bore or other passageway for coolant flow, the shank can be readily untrasonically tested and its strength is not compromised.. Operational reactor vessels may be backfit without having to remove and disassemble the baffle assemblies.