Some design aspects related to stresses and strains in high temperature piping

This paper is concerned with the differences which exist between piping design procedures for normal temperature usage and those for high temperatures. Some additional modes of failure must be considered in high temperature design, such as creep and creep ratchet, creep relaxation and elastic follow up.The paper discusses possibilities of calculating the influence of the high temperature effects in relation to the analysis of stresses and strains in piping systems. Stress categories and strain limits are developed with respect to typical systems in a sodium-cooled reactor and to steam piping in a gas-cooled high temperature power plant. Rules for dealing with high temperature piping are proposed, the intention being to ensure that these provide the same level of safety as that provided for class 1 piping in water-cooled reactors.