ASN Report 2022

After examining the environmental protection questions, ASN adopted four resolutions in turn, setting temporary requirements for the thermal discharges of the NPPs at Golfech, Bugey, Saint‑Alban, Blayais and Tricastin, for the period from 15 July to 11 September. ASN also instructed EDF to conduct reinforced monitoring of the aquatic environment, by means of sampling and measurements. These NPPs only resorted to the temporary provisions for a total of 24 days (9 days for Tricastin, 8 days for Bugey, 6 days for Golfech and 1 day for Saint-Alban). The Blayais NPP was able to maintain its electricity production without having to resort to these temporary provisions. The initial results of the reinforced environmental monitoring stipulated by ASN show no impact between the upstream and downstream of the NPPs concerned, whether in terms of physicalchemical parameters, or microbiology values (bacteria). No fish mortality or alteration of the health of the environment was identified between the upstream and downstream of the NPPs concerned. ASN also carried out inspections with respect to the implementation of these resolutions. It found no deviations from the provisions it had prescribed. Management of radioactive effluents during periods of drought The discharge flow of the watercourse can also prevent EDF from discharging the liquid effluents from the nuclear reactors. In order to limit the impact of these discharges on the receiving medium, ASN determined a minimum watercourse discharge flow value, for each riverside NPP, below which no radioactive effluent discharge is permitted. Below these values, EDF must store this effluent until the return of favourable watercourse discharge flow conditions. The NPPs have emergency tanks with additional effluent discharge capacity in order to deal with exceptional situations. Their use requires prior approval from ASN. During the course of 2022, ASN granted EDF permission to use one or two emergency tanks for the NPPs at Belleville-surLoire, Cattenom, Chinon, Dampierre-en-Burly, Nogent-surSeine and Saint-Laurent-des-Eaux, during periods in which the watercourse discharge flow levels were lowest, thus preventing it from discharging radioactive effluents. ABSTRACTS – ASN Report on the state of nuclear safety and radiation protection in France in 2022 15 Notable events 2022 A period of heatwave and drought has three main consequences for the operation of nuclear reactors. Operation of equipment participating in reactor safety during a heatwave The heatwaves led to high air temperatures, causing an increase in the temperature in the NPP premises. Within these premises, the correct working of the equipment contributing to the safety of the nuclear reactors is guaranteed up to a certain ambient temperature. Ventilation and air-conditioning equipment is needed to prevent this temperature from being exceeded. During the heatwaves of 2003 and 2006, EDF reinforced the ventilation and air-conditioning capacity of the premises containing the safety systems. The temperatures that nuclear reactors are required to deal with are defined in the safety case at the end of 2022; they are regularly reassessed, notably during the periodic safety reviews. These reassessments take account of climate change. During the heatwave episodes of the summer of 2022, the maximum temperatures recorded in the NPP premises remained below the temperatures considered in the safety case. ASN noted that these high temperatures had no consequences for reactor safety. The power produced by the reactors in a situation with high watercourse temperatures To contribute to cooling its reactors, a NPP takes water from a watercourse or from the sea. This water is then returned to the watercourse or the sea at a higher temperature, either directly (“once through” reactor), or after cooling in cooling towers (“closed loop” reactor), enabling the dissipation of some of the heat into the atmosphere. This water discharged by the NPP leads to an increase in the temperature of the watercourse between the upstream and downstream of the discharge point. Depending on the reactor, this increase ranges from a few tenths of a degree (closedloop) to several degrees (once-through). In order to manage the consequences for the environment, the thermal conditions of these discharges are regulated by ASN resolutions specific to each NPP. The prescriptions set apply limit values concerning the temperature of the cooling water discharged into the natural environment and the heating downstream of the NPP, along with the environmental monitoring procedures. Thus, when the temperature of the watercourse upstream of the NPP is too high, EDF must reduce the power output by the reactors, or even shut them down, in order to meet the limit values associated with the downstream temperature. Between July and September 2022, the heatwave and drought episodes led to a rise in the temperature of certain watercourses used to cool the NPPs, in particular the Rhône and Garonne rivers and the estuary of the Gironde. However, the security of the electricity grid and the preservation of natural gas and hydroelectric dam water in order to meet the needs of next autumn and winter, led EDF to ask for a temporary modification of the thermal discharge specifications for these NPPs. ASN will analyse the consequences of climate change on the safety of the NPPs and on protection of the environment, as part of the approach it has initiated with regard to continued operation of these installations up to and beyond 60 years.