Abstracts ASN Report 2019

wall and the Ventilation System (EDE) which, between the two walls, collects and filters residual leaks from the inner wall ĵĸĹłŅĸ ķļņĶĻĴŅĺĸє ĸņļņŇĴŁĶĸ Ňł ĸŋŇĸŅŁĴĿ ĻĴōĴŅķņ ļņ ŃŅļŀĴŅļĿŌ provided by the outer wall. Ҋ ĻĴŇ łĹ ŇĻĸ ĿĴŀĴŁʼnļĿĿĸ ĶłŁņļņŇņ łĹ ŇŊł ĶłŁĶŅĸŇĸ ŊĴĿĿņ ĴŁķ a metal liner covering the entire internal face of the inner wall. ׏ِ ה Áǝƺ ȅƏǣȇ ƏɖɴǣǼǣƏȸɵ ƏȇƳ ɀƏǔƺǕɖƏȸƳ ɀɵɀɎƺȅɀ In normal operating conditions, at power, or in reactor outage states, the auxiliary systems control nuclear reactions, remove heat from the primary system and residual heat from the fuel and provide containment of radioactive substances. They mainly comprise the reactor’s chemical and Volumetric Control System (RCV) and the reactor’s Residual heat Removal System (RRA). The role of the safeguard systems is to control and limit the consequences of incidents and accidents. This chiefly concerns the following systems: Ҋ the Safety Injection System (SIS), the role of which is to inject water into the primary system in the event of it leaking; Ҋ the reactor building Containment Spray System (EAS), the role of which is to reduce the temperature and thus the pressure in the containment, in the event of a major primary system leak; Ҋ the Steam Generators Auxiliary feedwater System (ASG), which supplies water to the SGs if the normal feedwater system is lost, thus enabling heat to be removed from the primary system. This system is also used in normal operation during reactor outage or restart phases. ׏ِ ו Áǝƺ ȒɎǝƺȸ ɀɵɀɎƺȅɀ ǣȅȵȒȸɎƏȇɎ ǔȒȸ ɀƏǔƺɎɵ The other main systems or circuits important for safety and required for reactor operation are: Ҋ the Component Cooling System (RRI) which cools a certain number of nuclear equipment items. This system functions in a closed loop between the auxiliary and safeguard systems on the one hand and the systems carrying water from the river or sea (heatsink) on the other; Ҋ the Essential Service water System (SEC) which cools the RRI system with water from the river or sea (heatsink). This is a backup system comprising two redundant lines. In certain situations, each of its lines is capable of removing heat from the reactor to the heatsink; Ҋ ŇĻĸ ĸĴĶŇłŅ ĴʼnļŇŌ ĴŁķ ŃĸŁŇ ňĸĿ ļŇ łłĿļŁĺ ĴŁķ ŅĸĴŇŀĸŁŇ System; Ҋ the ventilation systems, which contain radioactive materials by creating negative pressure in the rooms and filtering discharges; Ҋ the fire-fighting water systems; Ҋ the Instrumentation and Control (I&C) system, which processes the information received from all the sensors in the NPP. It uses transmission networks and sends orders to the actuators from the control room, through the programmable logic controllers or operator actions. Its main role with regard to reactor safety is to monitor reactivity, control the removal of residual heat to the heatsink and take part in the containment of radioactive substances; Ҋ the electrical systems, which comprise sources and electricity ķļņŇŅļĵňŇļłŁє Ļĸ ŅĸŁĶĻ ŁňĶĿĸĴŅ ŃłŊĸŅ ŅĸĴĶŇłŅņ ĻĴʼnĸ ŇŊł external electrical sources: the step-down transformer and the auxiliary transformer. These two external sources are supplemented by two internal electrical sources: the backup ķļĸņĸĿ ĺĸŁĸŅĴŇłŅņє ļŁĴĿĿŌё ļŁ ŇĻĸ ĸʼnĸŁŇ łĹ ŇłŇĴĿ Ŀłņņ łĹ ŇĻĸņĸ łĹĹі site and on-site sources, each reactor has another electricity generating set comprising a turbine generator and each NPP has an ultimate backup source, the nature of which varies according to the plant in question. Over the next few years, these latter resources will be supplemented by an “ultimate back-up” diesel generator set for each reactor. Pre-stressed concrete wall Pre-stressed concrete wall Metal sealing liner 900 MWe reactor containments 1,300 MWe/ 1,450 MWe reactor containments 1,650 MWe reactor containments Reinforced concrete wall Annulus Reinforced concrete wall Annulus Pre-stressed concrete wall Metal sealing liner Reactor containments ASN Report on the state of nuclear safety and radiation protection in France in 2019 281 ׏׎ ٲ THE EDF NUCLEAR POWER PLANTS 10