Event investigations at nuclear power plants in Sweden: Reflections about a method and some associated practices

The MTO-E method for event investigation is described in the light of almost 20 years of usage in the Swedish nuclear industry. Various problems are addressed in the context of the method, e.g. accident models, causality, the use of the barrier concept, the meaning of safety culture, and the process of going from problem identification to problem solving. It is argued that future applications of in-depth investigations should focus more on (innovative) methods when suggesting remedial actions as a consequence of information derived from event investigations.