This paper presents a cooperative learning activity on a nuclear power plant to develop students' reasoning skills on socioscientific issues. To this end, the steps in the implementation of the activity have been given in detail. The activity was implemented in an undergraduate course with senior preservice science teachers, whose reflections were obtained immediately after the implementation. The preservice science teachers' reflections showed that the activity was useful in terms of understanding the controversy associated with nuclear power plants and contributing to students' discussion skills and decision-making abilities on socioscientific issues.