Consideration of Hydraulic Loads in the Load and Resistance Factor Design (LRFD) of Class 2 and 3 Nuclear Pipes

Abstract

Recently, work was done to develop Load and Resistance Factor Design equations for Class 2 and 3 straight nuclear pipes for loads that cause primary stress. Unlike the Allowable Stress Design (ASD) method, used traditionally in the ASME B&PV Code, the Load and Resistance Factor Design (LRFD) method results in a known reliability index or probability of failure, Pf, for the piping. LRFD may provide other benefits for the design of piping too, such as design consistency with other industries (ACI, AISC, etc.) and sections of the ASME B&PV Code (e.g., Section XI), facilitation of risk analysis of piping systems, and elimination of unnecessary conservatisms. This paper presents the format of the LRFD equations and load combinations that address mechanical (hydraulic) loading, result of sudden valve closure for Service Levels B, and C or Loss-Of-Coolant Accident (LOCA) for Service Level D for straight pipes. Sample partial safety factors are provided for different values of piping reliability. Results address both carbon and stainless steel material for piping and operation temperature up to 600°F.