The stress state in a plasma-facing component (PFC) under high heat-flux (HHF) loads is the most important factor to determine the lifetime of the component. Stresses in a typical tungsten monoblock type PFC are produced by fabrication process and reactor operation where the component is subjected to HHF loads. In this study, both stress contributions were determined non-destructively by means of neutron diffraction technique. To this end, operational HHF loads were simulated using a high-power neutral hydrogen beam facility (GLADIS) to impose cyclic surface heating at 20 MW/m2. A dedicated small-scale mock-up was fabricated applying hot radial pressing technique to join four tungsten blocks to a CuCrZr alloy cooling pipe via a soft 0.1 mm thick soft copper interlayer. This thin copper interlayer was used to simplify the residual stress profile for this preliminary test. The neutron diffraction measurements were carried out, at room temperature, at two different high-flux reactors: FRM II and the HANARO. Separate stress-relieved tungsten and CuCrZr samples were examined as reference state. The 3D stress tensor was determined in the same external block of the mock-up for both measurements, scanning it from the front face of the tungsten block towards the inner wall of the CuCrZr pipe. The results obtained at these two neutron sources are in good quantitative agreement. Comparing them with the stress profiles before thermal loading, it appears that after the HHF test at GLADIS compressive stresses up to -800 MPa developed in the tungsten block near the interlayer, while the CuCrZr pipe was scarcely affected, probably since the tungsten block accommodated most of the thermal impact. While stress measurements very close to the interlayer might have been affected by spatial resolution issues and error in the reference lattice parameter, the results of these experiments clearly indicate the significant impact of HHF loads on the stress profiles in the tungsten blocks.
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