Two unusual aspects of safety component operation—abnormal environmental conditions and aging—are combined analytically. The result is implemented in a computer code to quantify a safety system figure-of-merit. In conjunction with a probabilistic approach employing a specified risk criterion, the analytical method has been applied to a reactor protection system to determine a desired component-qualified age. The effect of a preventive renewal program as a substitute for or complement to an age qualification program is also discussed. Substantial economic benefits should be realized from the implementation of the analytical method.