Abstracts ASN Report 2021

was again marked by a number of technical deficiencies which could not always be detected during the requalification of the equipment items concerned. The hydrostatic test of the primary system and the test of reactor 3 containment during its ten-yearly outage ran smoothly; the results comply with the safety requirements. Damage to the turbo charger of an emergency diesel generator set had a major impact on the duration of the refuelling outage of reactor 2 at the end of the year. Lastly, during reactor 2 and 3 outages, an abnormal corrosion phenomenon –not related to maintenance– was observed in the fuel assemblies; it required the implementation of compensatory measures and complementary analyses which are still in progress. The total number of signif icant events reported remains within the average for the EDF reactors, but an unusually high proportion of themwere rated level 1 on the INES scale, without this trend being able to be interpreted as a drift. As in 2020, the Cattenom site is prompt in its reporting of significant events. ASN notes that the significant events management process is well mastered on the whole and effectively mobilises the site players up to senior management level. In the area of fire risk prevention, the findings of the inspections reveal many deviations. ASN considers that this entire subject needs to be brought back under control, as regards, for example, the calorif ic potential in the premises, sectorisation, fire permit management, or the time taken to remedy anomalies. The site’s emergency management was assessed through an unannounced exercise with a scenario of accidental spillage of soda into the stormwater system. The ability of the site to set up the required emergency organisation, which was put to the test by kinetics of the scenario, proved to be robust. Areas for improvement were nevertheless identified in the choice of measures to deploy on the ground to cope with the speed of the simulated event. With regard to environmental protection, gaseous and liquid effluent discharges and waste management are well controlled, but the site still has weaknesses which are illustrated by the relatively high number of events. It was found that the management of deviations and threshold overshoots can be improved, notably because the times and the analysis parameters were not appropriate for the implementation of relevant and effective corrective actions. Controlling the risk of proliferation of microorganisms in the cooling towers still necessitates reinforced biocide treatments which have consequences on the aqueous discharges. Lastly, in the areas of radiation protection and occupational safety the picture remains contrasted: although some deviations observed in preceding years, such as the control of accesses in prohibited areas, have not been repeated, the number of events remains high, including concerning radiation protection fundamentals, such as the marking out of limited stay areas. The relative improvement in the second half of the year compared with the f irst, possibly linked to the awareness-raising efforts the site made with the outside contractors, must be confirmed on the ground and last over time. A few events occasionally highlighted weaknesses in the occupational safety culture. Chooz nuclear power plant The Chooz NPP operated by EDF is situated in the municipality of Chooz, 60 km north of Charleville‑Mézières, in the Ardennes département. The site accommodates the Ardennes NPP, called Chooz A, comprising reactor A (BNI 163), operated from 1967 to 1991, for which the f inal shutdown and decommissioning operations were authorised by Decree 2007‑1395 of 27 September 2007, and the Chooz B NPP, comprising two 1,450 MWe reactors (BNIs 139 and 144), commissioned in 2001. Reactors B1 and B2 in operation ASN considers that the overall performance of the Chooz B NPP with regard to nuclear safety, radiation protection and environmental protection is in line with ASN’s general assessment of the EDF plant performance. At the end of 2021, EDF detected stress corrosion-related cracks in the circuits connected to the main pipes of the primary system of the two reactors. This issue will lead to a large-scale inspection and repair programme in 2022. With regard to nuclear safety, ASN notes that despite a promising start to the year, the dynamic of progress in reactor operation observed for several years now was not fully maintained, with more specifically a deterioration in the conducting of reactor management operations in the second half of the year, which led to a significant rise in the number of signif icant events. The efforts made by the licensee in its plan to regain operating rigour must be maintained. Particular vigilance must be applied to the quality of work preparation and management of the transient operating phases. With regard to maintenance and the works associated with the reactor 2 refuelling outage, ASN considers that the inspection activities ran satisfactorily, over and beyond the problem linked to the spalling of the cladding of several fuel rods –which prolonged the outage and necessitated the implementation of specific reactor control measures. In the area of radiation protection, progress has been noted in the dose optimisation procedure. This trend must nevertheless be analysed in the context of a relatively low maintenance work load in 2021, which is more conducive to good results. It therefore remains to be confirmed. Inappropriate individual behaviours in terms of radiation protection culture and observance of the basic principles have moreover been observed. ASN considers that the site’s environmental protection organisation is on the whole satisfactory. Improvements 60 ABSTRACTS – ASN Report on the state of nuclear safety and radiation protection in France in 2021 REGIONAL OVERVIEWOF NUCLEAR SAFETY AND RADIATION PROTECTION