In northern France, near the town of Quimper, an old nuclear reactor called EL4 at Brennilis has been sitting unused for over thirty years. Shut down in 1985, it is now the oldest unfinished nuclear dismantling project in the country. The challenge of dismantling this reactor is complex, requiring specialized tools and careful planning. A robot named ARTUR, developed by EDF and Graphitech, is being designed to extract 216 transverse tubes from the reactor vessel, a task scheduled for completion by 2030. The entire project, supervised by a decree issued in 2023, is expected to finish by 2040 or 2041, with costs reaching hundreds of millions of euros. The EL4 reactor was commissioned in 1966 as a prototype to explore an alternative nuclear technology, using heavy water as a moderator and carbon dioxide as a coolant. It produced 70 megawatts of electricity and was the only French reactor of its kind. However, after nearly two decades of operation, it was permanently closed in 1985 due to strategic decisions that favored other nuclear technologies. At the time, there was no urgent need for dismantling, so the reactor was confined and repurposed as a storage site under a 1996 decree. In 2000, EDF took over the project, but progress remained slow, leaving Brennilis as France’s longest-running unfinished nuclear dismantling effort. Dismantling a nuclear reactor is far more complex than removing pipes or rubble. It involves handling irradiated materials, massive structures, and precision work within the reactor vessel. The EL4’s unique design makes it especially challenging, as no other French reactor shares its exact characteristics. This means that methods used elsewhere cannot be directly applied, requiring tailored solutions and extensive planning. The most critical phase involves removing the 216 transverse tubes inside the reactor vessel. To avoid exposing workers to dangerous levels of radiation, EDF and Graphitech are developing the ARTUR robot, designed specifically for this high-precision task. This stage, set for completion by 2030, highlights the project’s cautious approach, where every step is thoroughly planned and tested, even if it delays the overall timeline. The project has faced several legal and logistical hurdles over the years. A first partial dismantling decree was issued in 2011, but it remained incomplete due to uncertainties about waste management for long-lived radioactive materials. In 2018, EDF submitted a new comprehensive plan, which went through a public inquiry in 2021. Finally, in September 2023, a decree mandated EDF to fully dismantle the reactor. With the project expected to finish by 2040 or 2041, it serves as a test case for France’s ability to manage the entire lifecycle of nuclear installations. Lessons learned from Brennilis—such as robotic innovation, waste handling, and administrative coordination—could help streamline the dismantling of other aging reactors in the future.