Development of creep elastic follow-up factor solutions for piping design of high-temperature reactor under combined primary and secondary loadings

Abstract

In this study, creep elastic follow-up (EFU) factor solutions are developed for the piping design of high-temperature reactors. A straight pipe under combined primary and secondary loadings is considered for high-temperature piping. Axial tension, internal pressure, and bending moment are applied to the straight pipe as a primary loading condition. The thermal stress caused by the temperature gradient through the thickness is considered as a secondary loading. Applying the similarity between the EFU factor curve and primary-secondary creep strain curve, an exponential form is employed to obtain a scheme of the EFU factor solutions. The ratio of the primary stress to the total stress, and the creep exponent are selected as the variables that affect the EFU. Elastic-creep finite element (FE) analyses are performed, and the R5 Option 3 method is used for estimating the EFU factors. Based on the FE results, the creep EFU factor solutions are proposed by providing the values of the parameters in the scheme. The proposed creep EFU factor solutions are validated by comparing the stress relaxation curves predicted by the present EFU solutions with those predicted by the FE results.