Nuclear safety by numbers. Probabilistic risk analysis as an evidence practice for technical safety in the German debate on nuclear energy

The article explores the introduction of Probabilistic Risk Assessment (PRA) for nuclear energy in the two German states, the FRG and the GDR since the late 1960s. We argue that PRA - which promised to make potential dangers associated with the new technology calculable, comparable and seemingly controllable by reducing them to numerical terms - is best understood as an evidence practice, aiming to (re-)establish intersubjective agreement on nuclear safety through quantification. As such, the introduction of PRA was from the beginning also a political question, tied to the destabilization of alternative evidence practices. While in both the FRG and the GDR, the relativization of the promise of absolute safety inherent in the new method proved problematic, this was an even bigger obstacle in the socialist East. Although PRA ultimately failed to (re-)establish a societal consensus on nuclear energy in Germany, its institutionalization shaped the societal discourse on dangerous technologies.