[en] Experimental measurements of the thermal hydraulic conditions at the Maine Yankee spent nuclear fuel storage pool were made 25 days after reactor shutdown and the full core had been off-loaded for the ten-year vessel inspection. The GFLOW computer code was used to pre-predict the experimental results as a guide to designing the experimental program. GFLOW is a three-dimensional numerical model of natural circulation thermal-hydraulics, developed as a tool for spent fuel pool design and licensing. To compare predictive results with actual test data, a post-test GFLOW simulation using measured pool power levels and boundary conditions was exected after the measurements were completed. Both the measurements and the computer predictions indicate that the Maine Yankee fuel storage pool is very quiescent with nearly homogenous thermal conditions at any given elevation. A thermal stratification exists in the vertical direction with temperatures varying from 92⁰F(33⁰C) at the pool bottom to 99⁰F (37⁰C) at the top surface. The average fuel assembly exit temperature is 97⁰F (36⁰C) with a maximum coolant temperature in the hottest assemblies of approximately 104⁰F (40⁰C). The average fluid velocity in the pool predicted by GFLOW was 0.09 ft/sec (0.03 m/sec). Experimentally, velocities were found to be 0.0 +- 0.2 ft/sec. Temperatures and velocities were observed to fluctuate with time at any given location in the pool. Representative magnitudes of these fluctuations are +-2⁰F (+-1⁰C) for temperature and +- 0.05 ft/sec (.02 m/sec) for velocity. In general, the GFLOW predicted temperatures were within 1⁰F (0.5⁰C) of the measured results