Boundary layer effects from adsorption, desorption, and absorption of dissociated hydrogen in the cladding of nuclear thermal propulsion reactors.

The dissociation of the hydrogen molecule is rarely explored in the high-temperature flow of modern and historic nuclear thermal propulsion (NTP) engines. This study investigates the impact of absorption on highly-enriched and low-enriched uranium NTP reactors due to hydrogen dissociation surface reactions. Results show that with increasing temperature, dissociated hydrogen has a decreasing wall coverage but a significant crossflow velocity, as high as 81 mm/s, near the outlet due to absorption. This absorption changes the turbulent velocity profile while only having a small effect on the local Stanton number. Changing velocity profiles and mass loss to the wall can change mass flow rates, altering engine performance. Calculation and modeling via analytical solutions are unlikely as similar studies show non-uniqueness and existence issues at this study's R e w = 1.43. Follow-on computational fluid dynamic modeling is needed to fully capture the performance changes to the NTP engine. [Display omitted] • Notable hydrogen absorption into cladding begins at surface temperatures of 1500 K. • Highest temperatures cause the highest hydrogen absorption velocity near 81 mm/s. • Comparison to similar data shows the local Stanton Number is not largely impacted. • Axial increase in temperature may cause thermal gradients and flow circulation. • Others show R e w = 1.43 has multiple solutions and potential backflow at the wall. [ABSTRACT FROM AUTHOR]