[en] Prompt neutron decay constants were measured for a delayed critical, unmoderated and unreflected U metal sphere at the Oak Ridge Critical Experiments Facility. Prompt neutron decay constant was 1.1095±0.0013 μs^-1. This can be used to verify calculational methods, both deterministic and Monte Carlo neutron transport methods. This value is in agreement with the value from GODIVA I data corrected for effects of support structure (1.10±0.01 μs^-1) but has a much smaller error as a result of the large number (167) of the measurements here and the high degree of sphericity of the sphere