EPRI stabilized chromium coating to reduce radiation buildup

The Electric Power Research Institute (EPRI) has sponsored much research on methods to mitigate radiation buildup on out-of-core surfaces in light water reactors. As a result of this work a new method called stabilized chromium processing was developed for treatment of reactor piping and components. This treatment method has been shown to be highly effective in retarding radiation buildup under PWR primary system chemistry conditions. Initial coupon tests of the stabilized chromium process were very favorable with ten-fold activity buildup reductions. EPRI is now sponsoring additional development and testing of this preconditioning technique. Concurrently, other techniques for applying thin chromium films are also being investigated. This project was conducted to demonstrate the benefit of stabilized chromium processing by monitoring activity buildup on actual plant components over several fuel cycles. Initial measurements were made on test coupons exposed at Doel-2, a Belgian PWR. Short pipe sections were also preconditioned with the stabilized chromium process and installed in the reactor water cleanup (RWCU) systems at Peach Bottom-2 and 3. Additionally, thirty-seven steam generator manway diaphragms were treated using the stabilized chromium process. Components preconditioned with stabilized chromium and exposed to PWR primary coolant have shown exceptional resistance to activity buildup with reduction factors on the order of ten-to a hundred-fold less than reference materials. Similarly treated pipe sections exposed to the more oxidizing conditions of BWR primary coolant have not performed as well. (author)