The mission of the U.S. Department of Energy (DOE), Office of Nuclear Energy is to advance nuclear power in order to meet the nation’s energy, environmental, and energy security needs. Advanced high temperature reactor systems will required compact heat exchangers (CHX) for the next generation of nuclear reactor plant designs. A necessary step for achieving this objective is to ensure that the ASME Boiler and Pressure Vessel Code, Section III, Division 5 has rules for the construction of CHXs for nuclear service.

Construction of Alloy 800H diffusion bonded Printed Circuit Heat Exchangers (PCHEs) involves multiple controlled welding processes.  The primary diffusion bonding process creates a uniformly bond PCHE body featuring a microchannel core.  Secondary welding processes are needed to attach headers and nozzles to the PCHE body, forming a complete CHX.  The quality of these welding processes is ensured by following the appropriate ASME Sec. IX weld qualification procedures.  Headers and nozzles that must be welded onto the diffusion bonded PCHE body introduce weakness as the weld heat affected region locally stresses the underlying diffusion bond.

Experience in constructing both 316L and 800H PCHEs has given a set of acceptable attachment weld configurations and procedures.  Acceptable weld configurations and diffusion bonded block surface preparations are provided.  The integrity of attachment welds was directly tested through Hydrostatic pressurization.  This simply equality assurance test reliably leads to failure at poor attachment welds.  Failure of the PCHE core in a hydrostatic test was also achieved, but hydrostatic testing of the core structure is not considered practical as headers and head attachments will fail at far lower pressures than the PCHE core.


Guidelines for Welding Attachments Onto, and for Pressure Testing Of, Diffusion Bonded Heat Exchangers

Division / Sponsors: 
Pressure Vessels & Piping (PVP)


Paper Proceedings: https://asmedigitalcollection.asme.org/PVP/PVP2020/volume/83815

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