Abstracts ASN Report 2019

׏ِ ב Áǝƺ ȵȸǣȅƏȸɵ ɀɵɀɎƺȅ ƏȇƳ Ɏǝƺ ɀƺƬȒȇƳƏȸɵ ɀɵɀɎƺȅɀ The primary system and the secondary systems transport the energy given off by the core in the form of heat to a turbine generator set which produces electricity. The reactor coolant system comprises cooling loops, of which ŇĻĸŅĸ ĴŅĸ ŇĻŅĸĸ ĹłŅ Ĵ ӌӃӃׇ ĸ ŅĸĴĶŇłŅ ĴŁķ ĹłňŅ ĹłŅ ŇĻĸ ӄёӆӃӃ ĸё ӄёӇӈӃ ĸ łŅ ӄёӉӈӃ ĸ ʼnłĿňŇļłŁĴŅŌ łŊĸŅ ĸĴĶŇłŅ Ҏ ҏ ŇŌŃĸ reactors. The role of the reactor coolant system is to extract the heat given off by the core by means of circulating pressurised “primary water” or “reactor coolant”. Each loop, connected to the reactor vessel containing the core, comprises a circulating pump, called the “reactor coolant pump” and a Steam Generator (SG). The reactor coolant, heated to more than 300°C, is maintained ĴŇ Ĵ ŃŅĸņņňŅĸ łĹ ӄӈӈׇĵĴŅ ĵŌ ŇĻĸ ŃŅĸņņňŅļņĸŅё Ňł Ĵʼnłļķ ĵłļĿļŁĺє Ļĸ primary system is entirely situated within the containment. The primary system coolant transfers its heat to the water of the secondary systems in the SGs. The SGs are heat exchangers ŊĻļĶĻё ķĸŃĸŁķļŁĺ łŁ ŇĻĸ ŀłķĸĿё ĶłŁŇĴļŁ ĹŅłŀ ӆёӈӃӃׇŇł ӈёӉӃӃׇŇňĵĸņ through which the reactor coolant circulates. These tubes are immersed in the secondary system, which thus boils without coming into contact with the reactor coolant. Each secondary system primarily consists of a closed loop through which water passes, in the form of liquid in one part and in the form of steam in the other. The steam produced in the SGs is partially expanded in a high-pressure turbine and then passes through moisture separator-reheaters before entering the low- pressure turbines for final expansion, from which it passes to the condenser. Once condensed, the water is then sent to the SGs by the extraction pumps, followed by the feedwater pumps after passing through the reheaters. ׏ِ ג Áǝƺ ɀƺƬȒȇƳƏȸɵ ɀɵɀɎƺȅ ƬȒȒǼǣȇǕ ɀɵɀɎƺȅ The function of the secondary system cooling system is to condense the steam exiting the turbine. To do this, it has a condenser comprising a heat exchanger containing thousands of tubes through which cold water from outside (sea or river) circulates. On contact with these tubes, the steam condenses and can be returned in liquid form to the SGs (see point 1.3). The water in the cooling system heats up in the condenser and is then either discharged into the environment (once-through circuit) or, if the river discharge is too low or the heating too great for the sensitivity of the environment, is cooled in a Cooling Tower (TAR) –closed or semi-closed circuit. The cooling systems are environments favourable to the development of pathogenic micro-organisms. Replacing brass by titanium or stainless steel in the construction of riverside reactor condensers, in order to reduce metal discharges into the natural environment, requires the use of disinfectants, mainly by means of biocidal treatment. The copper contained in brass has bactericidal properties that titanium and stainless steels do not. Air cooling towers contribute to the atmospheric dispersal of legionella bacteria, whose proliferation can be prevented by stricter maintenance of the structures (descaling, implementation of biocidal treatment, etc.) and monitoring. ׏ِ ד Áǝƺ ƬȒȇɎƏǣȇȅƺȇɎ Ļĸ ŃŅĸņņňŅļņĸķ ŊĴŇĸŅ ŅĸĴĶŇłŅ ĶłŁŇĴļŁŀĸŁŇ ŃĸŅĹłŅŀņ ŇŊłׇĹňŁĶŇļłŁņѓ Ҋ the containment of radioactive substances liable to be dispersed in the event of an accident; to do this, the containments were designed to withstand the temperatures and pressures that would result from the most severe loss of coolant accident (double-ended circumferential rupture of a reactor coolant system pipe) and to ensure satisfactory leaktightness in these conditions; Ҋ ŅĸĴĶŇłŅ ŃŅłŇĸĶŇļłŁ ĴĺĴļŁņŇ ĸŋŇĸŅŁĴĿ ĻĴōĴŅķņє There are three containment model designs: Ҋ Ļłņĸ łĹ ŇĻĸ ӌӃӃ ĸ ŅĸĴĶŇłŅņ ĶłŀŃŅļņĸ Ĵ ņļŁĺĿĸ ŃŅĸіņŇŅĸņņĸķ concrete wall (concrete comprising steel tendons tensioned to compress the structure in order to increase its tensile strength). This wall provides mechanical pressure resistance and ensures ŇĻĸ ļŁŇĸĺŅļŇŌ łĹ ŇĻĸ ņŇŅňĶŇňŅĸ ļŁ ŇĻĸ ĸʼnĸŁŇ łĹ ĴŁ ĸŋŇĸŅŁĴĿ ĻĴōĴŅķє Tightness is provided by a metal liner covering the entire internal face of the concrete wall. Ҋ Ļłņĸ łĹ ŇĻĸ ӄёӆӃӃׇĴŁķ ӄёӇӈӃ ĸ ŅĸĴĶŇłŅņ ĴŅĸ ŀĴķĸ łĹ ŇŊł walls: the inner prestressed concrete wall and the outer reinforced concrete wall. Leaktightness is provided by the inner Steam discharge Moisture separators Feedwater ring Bundle wrapper Tube bundle Tube support platev Channel head Primary pumps Core instrumentation Control rod drive mechanisms Steam generator Reactor core Reactor vessel Vessel head Pressurizer A Steam Generator and a main primary system for a 1,300 MWe reactor 280 ASN Report on the state of nuclear safety and radiation protection in France in 2019 ׏׎ ٲ THE EDF NUCLEAR POWER PLANTS