The present report deals with the concept of potential exposure in nuclear and radiation safety, discussing policy aspects, safety assessments, risk considerations and probabilities. Contents: 1. Introduction; 2. Aspects of risk; 3. Policy for nuclear and radiation safety; 4. Safety assessments and risk considerations; 5. The implications of low probabilities; 6. Balancing potential and normal exposures; 7. Conclusions; Annex. Probability theory and its application in probabilistic safety assessment.