Leading nuclear commissioning for safe and reliable operation: Organizational lessons learned from Olkiluoto 3

Commissioning is a critical phase for ensuring the safe and reliable operation of nuclear power plants (NPPs). This study investigated the organizational lessons learned from the commissioning process of the Olkiluoto 3 (OL3) European Pressurized Reactor unit in Finland. Data were collected through semi-structured individual and group interviews complemented by document analysis. The analysis identified nine organizational lessons, which were structured into three categories: sensemaking lessons, organizational capability lessons, and coordination and leadership lessons. The findings suggest that commissioning should be treated as a deliberate phase of capability building, not merely as a period of technical system verification. The study complements technically oriented commissioning research by examining how organizational, interpretive, and leadership processes shape the conditions under which technical testing, acceptance decisions, and readiness assessments are carried out. It demonstrates that many challenges encountered during commissioning cannot be addressed solely through improved technical planning or procedural control, but require explicit attention to organizational sensemaking, learning, and leadership under uncertainty. The identified lessons may inform other nuclear construction, modernization and major-repair projects.