Appendix T in NH [7] provides three expressions for determining strain range [8] using elastic analysis and, if these rules cannot be satisfied, additional rules are provided,presumably less conservative, based on the results of inelastic analyses which require detailed constitutive models of material behavior under time varying loading conditions.For the CRBR, these behavioral models were a contractual provision based on RDT Standards. These applicable standards are no longer maintained and there have been numerous technical developments in this area since then [9]. Appendix T rules cover strain,deformation, creep and fatigue limits at elevated temperatures for 304SS/316 SS (816C), Alloy 800H (760C), 2.25Cr-1Mo (593C), 9Cr-1Mo-V (649C). Development of material models for materials not currently covered or for temperatures beyond their original range of verification will be a considerable effort. Modifications in Appendix T rules for higher temperatures and additional materials (e.g., Alloy 617, Hastelloy X/XR) may be needed.
