Driven by the operation conditions which involve high temperature and effectiveness, low pressure drop and relatively low alloy design stress levels, heal exchangers for the next generation of nuclear reactors need to be compact with high integrity construction. It has been demonstrated that the features and characteristics of a diffusion bonded heat exchanger, such as Heatric's Print Circuit Heat Exchanger (PCHE), Formed Plate Heat Exchanger (FPHE) and Hybrid Heat Exchanger, are able to meet the above requirements.One of the main challenges for such a compact exchanger is material, which needs to withstand the high temperature exposure for up to 60 years under a very corrosive environment. This requires materials to have good thermal stability, mechanical properties and corrosion resistance. Work on material selection suggests that Inconel alloy 617 is the leading candidate material for the high temperature exchangers.This paper describes the microstructure and mechanical properties of alloy 617 associated with the high temperature applications. The paper also considers the challenges associated with heat exchanger mechanical design at elevated temperature. It then focuses on the results from Heatric 's alloy 617 development programme. These results include the characterisation of as-received material, microstructural examination after diffusion bonding and mechanical testing. A demonstration PCHE core using alloy 617 has been successfully manufactured and has achieved the industry standard leak-tightness.
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