- 39 - ASN finds that the checks run by the licensee on the LLS are on the whole satisfactory. However, management of the anomaly sheets could be improved (Flamanville, Golfech, Saint-Alban). 2.4.6 Electrical transformers An electrical transformer is a converter able to modify the voltage and intensity of a current; an oil circuit is incorporated to act as an electrical isolator and as a coolant for removal of the heat produced. ASN finds that the checks run by the licensee on the electrical transformers are on the whole satisfactory. However, the inspectors did observe that certain oil analyses of these electrical transformers are unsatisfactory; some of the measured values in particular were imprecise and not even systematically measured and no justification was provided for the limit values being exceeded (Saint-Alban). 2.4.7 Fuel oil storage Each site has fuel oil storage tanks specifically for supplying each electricity generating set or combustion turbine. ASN finds that the fuel oil storage conditions could on the whole be improved. Fuel oil deliveries During the spot-checks, the inspectors found that on most sites, fuel oil delivery practices could entail risks of common-mode failure of all the electricity generating sets, in particular: the two electricity generating sets of the same reactor can be supplied by the fuel oil from the same delivery; the CPY series sites refuel the diesel generators from the SBO tank used as a buffer tank. This situation is liable to create a common-mode risk; as none of the sites ran checks on the conformity of the product at delivery, only the periodic analyses would be able to detect any nonconformity, thus delaying the implementation of any corrective measures. Corrosion During the visits to the fuel oil storage areas, the inspectors observed internal or external corrosion problems on the fuel oil piping and tanks on the majority of the sites (Civaux, Flamanville, Gravelines, Paluel, Fessenheim). This corrosion is facilitated by: water infiltration or leakage, (Civaux, Golfech); a lack of inspection of the condition of the piping and tanks (Flamanville, Golfech, Paluel). Over and above the problems of the cleanness of the premises (see section 2.4.2), the inspectors also observed a small leak from one fuel tank (Chooz). For the 1300 MWe and N4 series reactors, the inspections also revealed vulnerability of the fuel oil tanks areas to flooding. 2.4.8 Storage of oil and coolant fluid On the Paluel site, all the oil and coolant fluid needed for in-service make-up of the various electrical equipment items, is stored in a single place; this situation could lead to a common-mode failure risk for all this electrical equipment. 2.4.9 Management of the loss of electrical power supplies In the event of loss of a reactor's two electricity generating sets, EDF has drafted an inter-plant unit backup procedure (I-LHT) allowing rapid connection of this reactor to a backup generating set belonging to another reactor on the site.
RkJQdWJsaXNoZXIy NjQ0NzU=