Abandoned reactor in Brittany

At the heart of the Monts d'Arrée, under the often low skies of Finistère, lies a concrete and steel structure that has remained untouched for forty years. The Brennilis reactor, shut down in 1985, still awaits its complete dismantling.

Dismantling costs far exceed initial estimates

The total cost of dismantling the Brennilis reactor is estimated at 482 million euros by the Court of Audit, approximately twenty times the initial estimate. This figure highlights the complexity and challenges of decommissioning a nuclear facility.

Workforce and timeline for dismantling

Around a hundred people are currently working on the site, with the workforce expected to grow to more than 140 at the peak of activity. The final phase of dismantling began in December 2024, with a return to a bare site planned for 2041.

Unique reactor in a natural reserve

Le Yeun Elez, where the Brennilis reactor is located, is a peat basin of about 1,500 hectares that now hosts the national natural reserve of the Venec. The area is characterized by wetlands, peat bogs, and persistent mists, creating a landscape that contrasts sharply with the presence of a nuclear reactor.

Technical specifics of the Brennilis reactor

Officially named EL4-D, the Brennilis reactor was a 70 megawatt electric prototype with a moderated operation using heavy water and cooling with CO2. This technology was unique in France and led to the reactor being an isolated prototype without a twin.

Legal and procedural delays

The dismantling process faced delays due to legal challenges, including a 2007 ruling by the Council of State that annulled a 2006 decree. A new decree in September 2023 relaunched the procedure, and the Nuclear Safety and Radiation Protection Authority outlined a schedule for the dismantling in November 2025.

Challenges of dismantling

The first step in dismantling involves cutting a dozen kilometers of piping around the reactor vessel. This precision work will be followed by robot intervention on the highly irradiated core, as direct human involvement is not feasible. The first cuts of these circuits are expected to begin in 2026.

Environmental and legal constraints

The site’s unique nature, combined with environmental protections for the surrounding wetland area, has contributed to the high costs and complexity of the dismantling. The reactor’s technical complexity and the lack of standardized experience further complicate the process.

Symbol of cost discrepancies

Brennilis is a symbol of the gap between the costs announced at the launch of a nuclear program and the real costs of its dismantling. The discrepancy is partly due to the site's uniqueness, legal procedures, and environmental constraints.

Future of the site

By 2041, if the schedule holds, the landscape around Brennilis should return to its original appearance, with no visible trace of the reactor. Cranes and robots will continue to operate in the area until then, under the discreet gaze of the birds in the Venec natural reserve.