Selection Criteria for Clad Materials to Use with a 316H Base Material for High Temperature Nuclear Reactor Cladded Components

The clad selection criteria proposed in this work supports a design approach provided in [PVP2020-21469] for cladded component for high temperature nuclear service. The proposed design method guards the clad material against the creep-fatigue failure and ratcheting strain accumulation in elevated temperature nuclear service without the requirement of longterm material properties. However, it limits the type of clad materials that can be used with the existing Class A materials qualified for ASME Section III, Division 5 rules. The analysis approach and design rules allow the use of two types of clad materials - soft clads that creep much faster than the base material and hard clads that creep much slower and have higher yield stress than the base material. This work proposes selection criteria for such soft and hard clad materials to use with a Class A metallic alloy - austenitic steel 316H. The criteria are developed based on the effect of relative elastic modulus and creep rate on the long term stress redistribution between the 316H base and the clad material. The proposed clad selection criteria are applicable up to a design temperature of 750 degrees C and for 1% to 10% thick cladding. The selection criteria are evaluated on two materials - nickel and a molybdenum based alloy TZM - categorizing them as soft or hard clad for 316H base material.