METHOD OF CHANGING COOLANT FLOW PASSAGE IN PRESSURIZED WATER REACTOR AND UPPER CORE STRUCTURE IN PRESSURIZED WATER REACTOR

摘要

PROBLEM TO BE SOLVED: To reduce fluid exciting vibration of control rod of a pressurized water reactor. SOLUTION: In a pressurized water reactor having an upper core plate 15 pushing fuel assemblies constituting a core, a control rod cluster guide 29 guiding a control, rod cluster inserted in the core and an upper core support plate 21 supporting the upper core plate 15 through the control rod cluster guide 29, a shim plate 33 is additionally put between a middle flange 29c of the control rod cluster guide 29 and the upper surface of the upper core support plate 29 and a relatively large gap is added in between the lower flange of the control rod cluster guide 29 and the upper surface of the upper core plate 15 to change a coolant flow passage.