Experimental friction factor measurements in liquid sodium around a wire wrapped pin and application in Pronghorn SC code

A series of pressure drop measurements was obtained for liquid sodium flow around a wire wrapped fuel pin simulator centered in a circular test section. Friction factors were derived from the data, and a power law correlation was fit to the experimental data. The friction factor dataset and correlation were compared to established correlations for pipes and simple annular channels (Petukhov, 1970 & Colebrook, 1939) and for bundles of wire wrapped pins (Upgraded Cheng and Todreas, 2018). The friction factor measurements for the single wrapped pin channel fell between those used for simple annular channels and those for an interior bundle channel with the same hydraulic diameter as the experimental test section. This was expected as the single pin channel tested was more open than the interior channels in typical sodium fast reactor fuel bundles but still had a spiral wire wrap and several protrusions into the flow field. The custom power law correlation was implemented in Idaho National Laboratory's Pronghorn SC code and applied uniformly across all subchannel types for a 91-pin EBR-II example case, where it predicted assembly pressure drops approximately 6% higher than the built-in Upgraded Cheng and Todreas formulation, which assigns geometry-specific friction factors to interior, edge, and corner subchannels individually. This finding is limited to one experimental geometry and one assembly test case. The implementation is presented as a demonstration of the method for incorporating experimental friction factor correlations into Pronghorn SC, rather than a rigorous sensitivity study, though the quantified experimental uncertainty bounds on the fit correlation could be propagated through the code in future work to assess their effect on assembly-level outputs. Despite this limited generality, the study provides a compact technical contribution including a new friction factor dataset for liquid sodium flow around a wire wrapped simulated SFR fuel element, and the results inform friction factor treatments used in SFR thermal hydraulics modeling and code development. • New friction factor data and correlation fit for wire wrapped single pin in sodium. • Custom power law fit correlation derived with quantified uncertainty bounds. • Data lies between pipe and pin bundle correlations, consistent with geometry. • Pronghorn SC ΔP evaluated with new correlation. • Dataset useful for further validation of wire wrapped pin hydraulic modeling.