Compact heat exchangers (CHX) fabricated using the diffusion bonding process will be useful in the design and operation of Generation IV nuclear power plants.  The NDE challenges posed by CHX are quite different from those of their more familiar shell-and-tube cousins.  The examination scope is in three parts:  the welds joining the headers to the CHX body; the body’s solid perimeter, serving as the pressure boundary; and the channeled interior.  Current investigations are in support of a Section III Code Case regarding CHX fabrication and therefore focus on the post-fabrication examination ensuring adequate initial quality, though consideration is given to potential inservice examinations as well.

The welds joining the headers to the CHX body likely will be full-penetration set-on welds of conventional design.  Standard fabrication examinations will suffice, namely visual, dye penetrant and hydrostatic.  Additional examinations should be specified for the purpose of ensuring that the weld stresses have not caused unallowable separations between the diffusion-bonded layers of the body adjacent.

The diffusion-bonded solid perimeter should be examined to ensure that any presence of bonding failures are allowable.  Ultrasonic examination results are presented, obtained from test blocks containing simulated bond failures and from small CHX used during lab studies.

The channeled core of the CHX is geometrically complex and does not allow application of traditional NDE methods from the outside.  The CHX must be instrumented internally using sensors installed in ‘dummy’ layers.  Theory and experimental results are presented for a concept using networks of fiber optic strain gauges installed in the CHX interior.


Nondestructive Evaluation for Diffusion-Bonded Compact Heat Exchangers

Division / Sponsors: 
Pressure Vessels & Piping (PVP)


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

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