Abstracts ASN Report 2019

ȵƺȸƏɎǣȒȇ Ȓǔ ȇɖƬǼƺƏȸ ȸƺƏƬɎȒȸɀ ƳɖȸǣȇǕ ǝƺƏɎ ɯƏɮƺɀ The temperatures that nuclear reactors are required to deal with, as specified in the safety case, are regularly reassessed, notably during the periodic safety reviews. These reassessments take account of climate change. A heat wave has three main consequences for the operation of nuclear reactors. …ȵƺȸƏɎǣȒȇ Ȓǔ ɀƏǔƺɎɵ ɀɵɀɎƺȅɀ ƳɖȸǣȇǕ Ə ǝƺƏɎ ɯƏɮƺ In a heat wave, ventilation and air-conditioning systems are needed to guarantee the operation of the safety systems of the nuclear reactors. During the heat waves of 2003 and 2006, EDF reinforced the ventilation and air-conditioning capacity of the premises containing the safety systems. These systems, which are required in the event of a heat wave, undergo preventive servicing, inspection and maintenance work. The general operating rules for the reactors indicate the steps to be taken should this equipment fail. This entails taking special measures, or even shutting down the reactor, as necessary. In addition, EDF sets out special operating rules which, between April and October of each year, adapt the level of deployment of the internal organisations on the basis of the weather forecasts. «ƺƏƬɎȒȸ ƬȒȒǼǣȇǕ ƏȇƳ ɯƏɀɎƺ ȅƏȇƏǕƺȅƺȇɎ ǣȇ Ɏǝƺ ƺɮƺȇɎ Ȓǔ ƳȸȒɖǕǝɎ Ȓȸ ǼȒɯ ɯƏɎƺȸ ǼƺɮƺǼɀ Nuclear reactors must be permanently cooled in order to remain safe. Water is thus taken for this purpose from a watercourse or from the sea. A period of drought can lead to a drop in the level and discharge of a watercourse. The licensee must permanently ensure that these remain sufficient to cool the safety systems. These parameters are specific to each NPP. The discharge of the watercourse also affects the dispersal of liquid effluents from the nuclear reactors. For each NPP, ASN sets a minimum watercourse discharge value at which effluent discharges are possible. Below this discharge rate (low water situation), effluent discharges are prohibited and the licensee has to store the effluents produced. !ȒȇɎȸȒǼǼǣȇǕ ɎǝƺȸȅƏǼ ƳǣɀƬǝƏȸǕƺɀ The water intake from watercourses or the sea to cool the reactor is generally speaking discharged at a higher temperature, either directly, or after cooling in the cooling towers, enabling some of the heat to be dissipated into the atmosphere. In the case of NPPs using a watercourse, ASN has for each site defined the conditions for discharge of the water used for cooling. In order to protect the environment, the ecosystem in particular, limit values are set for the heating of the watercourse as a result of operation of the NPP, as well as for the temperature of the water downstream of the plant. If these limit values are exceeded, the licensee shall reduce the power of the reactor or shut it down. Since 2006, ASN has incorporated measures into the regulations covering NPP discharges, to ensure advance definition of the operations of NPPs in exceptional climatic conditions leading to significant warming of the watercourse. These special provisions are however only applicable if the security of the electricity grid is at stake. Temporary relaxation of the limit values for the thermal discharges may also be authorised by ASN, at EDF’s request, if needed by the electricity grid, as was the case during the heat waves of 2003 and 2006. In this case, environmental monitoring is reinforced. (ɖȸǣȇǕ Ɏǝƺ ǝƺƏɎ ɯƏɮƺɀ Ȓǔ א ׎׏ ח ً 0(I ǝƏƳ ɎȒ ɀǝɖɎ ƳȒɯȇ ɀƺɮƺȸƏǼ ȸƺƏƬɎȒȸɀ ƏȇƳ ȸƺƳɖƬƺ Ɏǝƺ ȵȒɯƺȸ Ȓǔ ɀȒȅƺ ȒɎǝƺȸɀِ «0JÈn ÁX…z z0á³ ڙ ¨ȸȒɎƺƬɎǣȇǕ z¨¨ɀ ǔȸȒȅ ǝƺƏɎ ɯƏɮƺɀ ƏȇƳ ƺƏȸɎǝȷɖƏǸƺɀ In 2019, France experienced several heat wave episodes, plus the earthquake ƏɎ nƺ ÁƺǣǼ Ȓȇ ׏׏ ژ zȒɮƺȅƫƺȸ אژ ׎׏ ח ِ Áǝƺ ȇɖƬǼƺƏȸ ȸƺƏƬɎȒȸ ɀƏǔƺɎɵ ƬƏɀƺɀ ɎƏǸƺ ƏƬƬȒɖȇɎ of this type of natural hazard. 20 ASN Report on the state of nuclear safety and radiation protection in France in 2019