A significant leak occurred on the valve of a tank containing 33% hydrochloric acid located within a non-controlled area of a nuclear power plant. A total of 58 m³ of acid had leaked into a catchpit. Hydrochloric acid is added to the water of the cooling-tower circuit to prevent scale build-up. The plant operator had the acid transferred to the cold-water tank, which is used to store condensate from the cooling tower before it is reinjected in the plant’s cooling system. It therefore injected the acid into a circuit that is used to discharge drips and storm water from the acid-handling area. The operation started at 5:45 p.m. on 23 July and ended at 2:00 p.m. the following day. On 29 July, the operator discovered that a section of the pipe on the circuit had completely broken off and that all the acid had flowed onto the floor. A portion of the acid drained into the groundwater, which was treated. On 6 August, France’s Nuclear Safety Authority (ASN) asked the operator to provide an environmental assessment proving that it had not exceeded the acid discharge thresholds.

The post-accident analysis showed that, in spite of chemical analyses starting at 8:30 p.m. on 23 July (before completion of the transfer) which showed it to be ineffective, acid continued to be injected into the cold-water tank until completion. In addition, the pipe that broke off had never been maintained and was not even identified on the plant’s P&ID diagrams.

This event did not affect the safety or radiation protection at the plant.