We argue that the post-Fukushima nuclear safety debates in the United States and Europe fundamentally altered the definition of nuclear safety. In the United States, the industry effectively took control by strengthening technical measures as the solution to nuclear safety concerns. In France, technical solutions were part of the process, but they were less dominant than in the United States and were overshadowed by larger organizational shuffles. The European Union, in contrast, engaged in a drawn-out debate over the very definition of nuclear safety, resulting in a stress test initiative that, while cumbersome and frustrating to many, included truly deliberative elements and ultimately revealed just how precarious the definitions of control and nuclear safety were.