In conjunction with transfer of fresh fuel carried out on unit two at the Loviisa power plant on 28 February 2017, one fuel assembly came loose from the loading machine’s catch and fell into the transfer basket at the bottom of the fuel transfer basin. The incident did not pose any direct threat in terms of nuclear or radiation safety. Upon discovering the incident, the transfer of fuel was immediately halted, Fortum launched an incident investigation, and reported the incident to the Finnish Radiation and Nuclear Safety Authority (STUK).
The direct cause of the incident was identified as a mechanical malfunction of the fuel loading machine combined with human factors. In conjunction with the inspections, changes were detected in the protective housing and the lower end cap of the fuel assembly that fell, but it is safe to handle the fuel assembly and it can be returned to the fuel manufacturer.
“We take the incident seriously. The fuel loading machine is included in the power plant’s maintenance and inspection programme. After the incident, the coverage of the maintenance programme has been assessed and corrective actions have been launched. Also procedures and guidelines related to fuel handling have been assessed. Based on the assessment, the guidelines and procedures have been further defined both in terms of verification of the work and human factors. To ensure implementation of the updated guidelines and procedures, the work done at the loading machine is supervised by an expert, who also provides training for the work. This third person also helps in paying special attention to critical phases and human factors,” explains Thomas Buddas, the deputy director, responsible for nuclear safety at Loviisa power plant.
Loviisa power plant rated the incident at a level 1 on the international nuclear event scale (INES), i.e. as an anomaly affecting safety. The Finnish Radiation and Nuclear Safety Authority (STUK) has confirmed the rating.
Thomas Buddas, Deputy Director, Loviisa Power Plant, tel. +358 10 455 3710