4. Security

The preceding paragraphs have detailed the precautions taken during design, construction and operation to ensure reactor safety.

Operating conditions obviously contribute to achieving good safety, but operation is also a means of verifying the effectiveness of these design precautions, at least for the most expected situations.

We're not going to talk about unit availability, a legitimate concern of operators and a good one at that, because its link with safety can be ambiguous. There is no shortage of examples of availability taking precedence over safety. This was more or less the case at both Three Mile Island and Chernobyl. Conversely, a well-operated unit with well-monitored and well-maintained equipment is likely to have both a good level of safety and good availability.