b'observed. The surface parameters anddeviation. Currently, surface chemistryFigure 5. Selected results from VCU-surface chemistry after flow boilingis being investigated. led project: The top part of the figure overviews flow boiling and surface critical heat flux tests, conducted atReferences: characterization studies for CHF at atmospheric pressure, evidenced a[1.] INL Report, edited by G. Su, M.atmospheric pressure, accompanied slight increase in surface roughnessBucci, and P. Sabharwall, Inves- by surface characteristics and surface with notable changes in wettabilitychemistry of the tested Cr-coated tigations on Thermal-hydraulicZr-4. Bottom shows examples of void associated with the formation ofBehavior of Accident Tolerant Fuelfraction measurement on bare Zr4, Cr surface oxides and adsorbed carbona- Cladding Materials, INL/EXT-19- coated Zr4 with PVD coating, and Zr4 ceous species. CHF on ATF materialswith CS coating heater rod at a heat 56455, January 2020. flux of 1.20 MW/m2 with a mass flux of FeCrAl alloys (APMT, C26M)) were750 kg/m2s and subcooling of 76oC. similar to bare Zr-4 within the 10%The results clearly show the enhanced void fraction on the rougher surface (Cr coated Zr4 with CS coating) resulting in HTC improvement.2020|AFC ACCOMPLISHMENTS 43'