Laboratory evaluation of low cobalt wear materials for nuclear applications

The wear and corrosion of high cobalt wear resistant alloys, commonly used in nuclear power plant components, represents a significant source of cobalt contamination to the primary coolant system. Replacement of these materials with cobalt free alloys will result in a significant reduction in post-shutdown radiation fields and associated occupational radiation exposures. Several materials screening programs have been performed world-wide and have resulted in the selection of a variety of cobalt-free alloys, particularly for valve applications. The NOREM series of alloys, developed on an Electric Power Research Institute (EPRI) sponsored program, along with other candidates alloys, were tested in gate valves in an EPRI sponsored program run by the Atomic Energy of Canada Limited. A screening program run in the UK resulted in the selection of Delcrome 910 for valve applications. A similar alloy, Everit 50 was selected for use in the German PWR program. The program reported here evaluated the wear behavior of some of the same alloys. Corrosion tests were also performed with special attention being given to simulated off-normal chemistries such as storage and wet-lay up, decontamination and air-accident conditions. (authors). 5 figs., 3 tabs., 4 refs