Effect of PVD-coated chromium on the subcooled flow boiling performance of nuclear reactor cladding materials

We elucidate the separate effect of a thin Cr coating deposited by physical vapor deposition (PVD) on subcooled flow boiling performance zircaloy-4. First, we run experiments prototypical zircaloy-4 surfaces mimicking scratch pattern and surface roughness nuclear reactor claddings. Then, PVD-coat 0.3 µm thick chromium layer same exact repeat investigations. All are using deionized water at atmospheric pressure, flowing 1 × 3 cm2 rectangular cross section channel rate 1000 kg/m2/s subcooling 10 K. measure average temperature increasing heat fluxes, covering wide range transfer regimes, from single-phase forced convection to crisis. also record high-speed videos process, which postprocess bubble nucleation site density, growth time, departure diameter frequency. The analysis reveals that, while does not seem change morphology, it improves wettability. However, decreases critical flux. causes an increase temperature, reduction density. concurrence these observations indicates that size sites, conformally covered coating, may be cause deterioration. confirm this hypothesis repeating FeCrAl sample prepared tested protocol as sample, but with different initial texture.