Thermal fatigue phenomena in normally stagnant branch lines connected to the primary loop of pressurized water reactors has been identified as a primary cause for at least ten pipe cracking events in the past decade. Current prediction and inspection of at-risk piping is based on semi-empirical models, derived on the basis of low-resolution experimental data. This data does not include sufficient information on contributing factors that lead to thermal boundary development and fluctuation in dead-ended branch lines. Without comprehensive, high-resolution data of the phenomena involved, CFD models attempting to account for the re-laminarization or quasi-laminar flow that persists in the branch line cannot be validated.Validated CFD models for dead-ended branch line flow conditions will greatly expand the predictive capabilities the method currently offers. To build the database necessary for related CFD validation campaigns, 3D high-resolution measurements were made in the branch line of an experimental facility built at the University of Michigan. The facility is a scaled coolant flow loop with a reduced main line diameter. Nuclear power plant coolant loop flow rates near 10 m/s were achieved for study. High-resolution, 3D velocity field data in the dead-ended branch line was obtained using Tomographic Particle Image Velocimetry (T-PIV) techniques. With this data as a basis for validation, CFD models such as Low-Re will be able to accurately predict flow phenomena in dead-ended branch line simulations where the branch line diameter, opening geometry, or piping component (elbow) locations are altered.