Optimizing thermal and radiation effects for bacterial inactivation

The temperatures required for dry-heat spacecraft sterilization have been known to degrade heat-sensitive components. Thermoradiation, the simultaneous application of dry heat and gamma radiation, can provide the same degree of microbial inactivation as dry heat alone while substantially reducing component degradation. This is made possible by the synergistic effects produced when relatively low levels of these agents (e.g., 90 to 350 krads and 60° to 105°C) are applied simultaneously, thus permitting the use of lower temperatures and a reduced duration of heat exposure. The effects of temperature, radiation dose rate, and relative humidity on microbial inactivation during thermoradiation exposure have been established.This experimentation was supported by NASA Contract No. W-12853.