Simulated Environmental Tests for Selected Advanced Technology Fuel Cladding Solutions

Abstract

Current development on advanced technology fuel (ATF) claddings is aiming at improved high temperature integrity of new candidate materials designed on existing zirconium cladding materials. To assess their performance in commercial use, characterization of newly proposed materials is essential. The primary requirement for the cladding materials is the ability to tolerate loss of cooling for a significant period without failing. The tests in this work were performed on different types of coated Zr-alloys in a high temperature steam furnace in flowing steam conditions at 1100 °C for 500 s, 1200 °C for 1800s, and 1300 °C for 300 s. In addition, autoclave exposures were performed in simulated pressurized water reactor (PWR) water chemistry to confirm the material viability in normal light water reactor (LWR) operating conditions. After autoclave and steam furnace tests, exposed specimens were characterized using a Zeiss Crossbeam 540 field emission gun-scanning electron microscope (FEG-SEM) equipped with a semiquantitative energy dispersive X-ray spectrometer (EDS). Oxide and coating layers were imaged using secondary electrons and elemental composition of the layers were determined using selected area (SA) and point analyses. In addition, elemental maps were collected from specific areas of interest. Most of the tested specimens indicated detached coating layer. Varying amounts of cracking in the coating materials were present. Some of the cracks extended even into the base material. Based on this study, further developments of ATF cladding solutions are needed through international collaboration.