Measurements of induced radioactivity in electron- and photon-irradiated beef

Samples of beef were irradiated with electrons of approx. 10- and 13.5-MeV energies or with 60Co gamma-ray photons (1.17 and 1.33 MeV). Induced radioactivity was measured with a gamma-ray spectrometer, consisting of a Ge(Li) detector and a multichannel analyzer. No induced radioactivity could be detected in the photon-irradiated samples; also for 10-MeV electrons the activity was below the detection limit. The irradiation by 13.5-MeV electrons, however, resulted in measurable radioactivity and the amount of 13N-activity was in agreement with previously calculated values. These measurements confirm previous conclusions that irradiation of food with electrons at 10 MeV or even at 13.5 MeV does not constitute any health risk due to radioactivity. Part of the induced radioactivity from 13.5-MeV electron irradiation is due to neutron capture, and the results suggest that several neutron sources contribute to the measured radioactivity.