Introduction of Hot Isostatically Pressed, Reactor Coolant System Components in PWR Plant

This paper presents an overview of the work undertaken by Rolls-Royce to introduce Hot Isostatically Pressed (HIP) components into Pressurised Water Reactor plant, and also results of non-destructive and destructive examinations of a thick-walled pressure vessel. It presents the work from a design justification/manufacturing quality assurance perspective, rather than from a pure metallurgical perspective. Although the HIP process is not new, it was new in its application to Rolls-Royce designed nuclear reactor plant. As a consequence, Rolls-Royce has implemented an evolving, staged approach, starting with HIP bonding of solid valve seats into small bore valve pressure boundaries. This was followed by powder HIP consolidation of leak-limited, thin-walled toroids, and has culminated in the powder HIP consolidation of thick-walled components. The paper provides an overview of each of these stages and the approach taken with respect to justification. Mechanical testing and metallurgical examination results of sample material taken from different sections of a thick-walled component are presented. A full range of test results is provided covering, as examples: tensile, charpy and sensitization susceptibility. Differences in weldability between the HIPed and the previous forged form are also documented. The paper describes the benefits that Rolls-Royce has realised so far through the introduction of HIPed component. Structural integrity benefits are described, such as improved grain structure, mechanical properties, and ultrasonic inspection. Project-based benefits are also described, such as provision of an alternative strategic sourcing route, cost and lead-time reductions.