This experiment was a continuation of studies begun in 1956 to determine the radiation doses recieved by the survivors of the Hiroshima and Nagasaki nuclear detonations. The "Ichiban" critical assembly was designed and constructed at Los Alamos Scientific Laboratory to provide a simulant for the Hiroshima bomb with respect to radiation "leakage" and spectrum. It was operated at steady-state power levels while neutron and gammaray dose measurements were made. The results were corrected for room scattering and normalized to dose per fission. The first collision neutron dose measured at a distance of 9.5 meters was 7.7+-0.3*10-17 tissue rads per fission. Coupled with the mean dose per neutron of 1.14 * 10-9 rad/neutron/cm2, this measurement represented a total fast neutron leakage of 0.77 +- 0.03 neutrons per fission.