High temperature deformation behavior of Indian PHWR Calandria material SS 304L

Abstract

Calandria, a horizontal stepped cylindrical vessel, houses the fuel channels (reactor core) of Indian Pressurized Heavy Water Reactors (IPHWRs). The Calandria and its support assembly is made from austenitic stainless steel SS 304L grade. Post Fukushima nuclear accident (2011), the realistic assessment of time line of structural degradation of Calandria during the progression of a postulated severe accident has become an important requirement. This calls for a detailed finite element analysis of Calandria assembly where material deformation behavior owing to both creep and plasticity up to very high temperatures arising during accident progression has to be modeled.Although stainless steel SS 304L finds wide application in nuclear industry, the material properties up to very high temperatures as required for present case, are not available in the open literature. Hence, in the present work, the tensile and creep-stress rupture properties of SS 304L have been generated for temperatures up to 1100 °C. Engineering stress-strain curves, yield strength, ultimate tensile strength, uniform elongation as well as Ramberg-Osgood fitting parameters are evaluated from the tensile test data. Creep test data is processed to evaluate creep curves, minimum creep rate, Norton-Bailey creep law parameters as well as Larson Miller Parameter based correlation for prediction of stress rupture life. The generated properties would be useful as material inputs to carry out realistic structural integrity assessment of Calandria assembly for loads arising under accident conditions.