THERMOMECHANICAL ANALYSIS OF PRESSURE VESSELS

Regulatory Guide (RG) 1.161 and American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code), Section XI, Nonmandatory Appendix K contain stress intensity factor (SIF) equations for both the internal pressure and thermal gradient loading cases. However, the technical basis behind these equations was developed only for R-i/t = 10, were R-i is the inner vessel radius and t is the vessel thickness. While this geometry is appropriate for most pressurized water reactors (PWR), most boiling water reactor (BWR) vessels have R-i/t = 20. This paper explores the validity of applying these SIF equations to BWRs. This confirmatory work includes calculating SIF by independent methods. The one-dimensional heat equation is solved to provide a physical basis for the thermal stresses.