Superphénix was a groundbreaking nuclear reactor designed to produce more fuel than it consumed, making it a type of fast breeder reactor. These reactors use a specific kind of nuclear fuel—plutonium and enriched uranium—that allows them to generate more fuel than they use, potentially offering a more sustainable energy source. Located in Creys-Malville, Isère, France, it was the world's largest fast breeder reactor, developed through a joint effort by France's EDF, Italy's Enel, and Germany's SBK under the NERSA consortium. The reactor was connected to the national power grid in 1986 but was shut down in 1997 by the government led by Prime Minister Lionel Jospin. This decision was later described as primarily political, rather than driven by technical issues. According to a parliamentary report from April 1997, continuing to operate Superphénix was considered less expensive than shutting it down immediately. This economic reasoning played a key role in the decision to keep the reactor running, despite its limited operational time. The reactor had only been in normal operation for about four and a half years between 1985 and 1996, with much of its time spent in testing, partial operation, and maintenance. The official shutdown was formalized in December 1998, nearly a year and a half after the initial decision to close it. Superphénix was built on the success of an earlier prototype, the Phénix reactor, which was a 250-megawatt fast breeder reactor launched in 1973 at Marcoule. That reactor helped validate the principles behind fast breeder technology. Building on this experience, France aimed to leap directly to a much larger reactor—1200 megawatts—without going through an intermediate size. Construction of the Creys-Malville site began in 1976 and took ten years to complete. The project was a multinational effort, involving not only French companies but also Italian Enel and German SBK. The shutdown of Superphénix marked the end of a significant industrial and technological ambition for France. At the time, the country held a rare technological advantage in using nuclear waste as a source of energy, a capability that could have reshaped the global approach to nuclear energy and the management of fissile materials. However, political decisions led to the end of this project. Today, the Creys-Malville site remains important not for its operation, but for its ongoing dismantling. This process, expected to be completed by 2030, is one of the largest and most complex in the world, highlighting the long-term challenges of nuclear infrastructure.