Improved Reliability, Maintainability and Safety Through Elastomer Upgrading

Abstract

Equipment in nuclear plants has historically contained whatever elastomer each component supplier traditionally used for corresponding non-nuclear ser- vice. The resulting proliferation of elastomer com- pounds, many of which are far from optimal for the service conditions (e.g., pressure, temperature, radiation, etc.), has multiplied the costs to provide station reliability, maintainability and safety. Cost-effective improvements are being achieved in CANDU@ plants by upgrading and standardizing on a handful of high performing elastomer compounds. These upgraded materials offer significant gains in service life over the materials they replace (often by factors of 2 or more). This rationalization of elastomer compounds also facilitates the EQ+ process for safety-related equipment. Detailed test data on aging is currently being generated for these specific elastomers, encompassing the conditions and media (air, water, oil) common in CANDU@ service. Two key elements characterize this testing. First, each result is specific to the compound used in the test, and second, it is specific to the tested failure mode (e.g., compression set, extrusion, fracture, etc.). Having fewer, but more thoroughly tested com- pounds, avoids the penalty (associated with poorly characterized materials) of having to replace parts prematurely because of conservatism, while maintaining safe, reliable service. This paper provides an overview of this approach covering: the benefits of compound rationalization the how and why of establishing relevant failure criteria appropriate quality assurance to maintain EQ procurement, storage and handling guidelines monitoring and predicting in-service degradation.