This section could be titled ‘learning from experience’. This issue is some­what broader, however, as necessitated by a complex system such as nuclear energy. This issue becomes extremely important to support the justification of a new nuclear program, because the experience must be gained rapidly, essentially without the benefit of prior operating experience by the operat­ing company. It has been found very useful to study abnormal events that have occurred in nuclear power plants in the past. By this means the newly initiated operating staff get a clear picture of how mistakes have been made, how consequences of those mistakes have been dealt with, and how future operation can benefit from the lessons learned (Duffey and Saull, 2003, 2008). Further, it has been found that the causes, patterns and frequencies of failure are very similar across a wide range of human endeavour. The nuclear energy enterprise stands out (Weick and Sutcliffe, 2007) as a high-performance industry in terms of its low risk of high-consequence accidents.