The gamma-ray dose rate and the fast neutron flux have been measured in air from a source of water shortly after irradiation in the Materials Testing Reactor. Gamma rays from N16 and neutrons from N17 have been detected. From the measurements and the known geometry, the cross sections for the O16 (n, p) N16 and the O17(n, p) N17 reactions averaged over the fission neutron spectrum have been deduced to be 0.019 mb and 0.0052 mb, respectively. The results are compared with other measured values and theoretical estimates.