Material Selection for Accident Tolerant Fuel Cladding

Abstract

Alternative cladding materials are being investigated for accident tolerance, which can be defined as >100X improvement (compared to current Zr-based alloys) in oxidation resistance in steam environments at >1200°C for short (<4h) times. After reviewing a wide range of candidates, current steam oxidation testing is being conducted on Mo, MAX phases and FeCrAl alloys. Recently reported low mass losses for Mo in steam at 800°C could not be reproduced. Both FeCrAl and MAX phase Ti2AlC form a protective alumina scale in steam. However, commercial Ti2AlC that is not single phase, formed a much thicker oxide at 1200°C in steam and significant Ti02, and therefore may be challenging to use as a cladding or a coating. Alloy development for FeCrAl is seeking to maintain its steam oxidation resistance to 1475°C, while reducing its Cr content to minimize susceptibility to irradiation assisted Cr-rich a ’ formation. The composition effects and critical limits to retaining protective scale formation at >1400°C are still being evaluated. Keywords: Accident tolerant LWR Fuel cladding, FeCrAl, Mo, Ti2AlC, A120 3, high temperature steam oxidation resistance.