Abstracts ASN Report 2019

or plutonium nuclei, said to be “fissile”, emit neutrons which in turn trigger other fissions: this is the chain reaction. The nuclear fissions give off a large amount of energy in the form of heat. The water in the reactor coolant system, which enters the ĿłŊĸŅ ŃĴŅŇ łĹ ŇĻĸ ĶłŅĸ ĴŇ Ĵ ŇĸŀŃĸŅĴŇňŅĸ łĹ ĴĵłňŇ ӅӋӈխ ё ĻĸĴŇņ ňŃ as it rises along the fuel rods and comes out through the top at a temperature of close to 320°C. At the beginning of an operating cycle, the core has a considerable energy reserve. This gradually decreases during the cycle, as the fissile nuclei are consumed. The chain reaction and thus the power of the reactor is controlled by: Ҋ the insertion of “control rod clusters” containing neutron- absorbing elements into the core to varying extents. This enables the reactor’s reactivity to be controlled and its power adjusted to the required production of electricity. Gravity dropping of the control rods is used for emergency shutdown of the reactor; Ҋ adjustment of the concentration of boron (neutron absorbing element) in the reactor coolant system water during the cycle according to the gradual depletion of the fissile elements in the fuel; Ҋ the presence of neutron-absorbing elements in the fuel rods which, at the beginning of the cycle, compensate the excess core reactivity after partial renewal of the fuel. At the end of the cycle, the reactor core is unloaded so that some of the fuel can be replaced. ňņĸņ ŇŊł ŇŌŃĸņ łĹ ŁňĶĿĸĴŅ ĹňĸĿ ļŁ ŇĻĸ ņѓ Ҋ uranium oxide (UO 2 ҏ ĵĴņĸķ ĹňĸĿņ ĸŁŅļĶĻĸķ ŊļŇĻ ňŅĴŁļňŀіӅӆӈׇŇł a maximum of 4.5% by mass. These fuels are fabricated in ņĸʼnĸŅĴĿ ŅĸŁĶĻ ĴŁķ ĹłŅĸļĺŁ ŃĿĴŁŇņё ĵŌ ŅĴŀĴŇłŀĸ ĴŁķ Westinghouse; Ҋ fuels consisting of a mixture of depleted uranium oxide and plutonium oxide (MOX). MOX fuel is produced by Orano’s Melox plant. The maximum authorised plutonium content is ĶňŅŅĸŁŇĿŌ ņĸŇ ĴŇ ӌєӃӋՌ ҎłŁ ĴʼnĸŅĴĺĸ ŃĸŅ ĹňĸĿ ĴņņĸŀĵĿŌҏ ĺļʼnļŁĺ an energy performance equivalent to UO 2 ׇĹňĸĿ ĸŁŅļĶĻĸķ Ňł 3.7% uranium 235. This fuel can be used in the twenty-eight ӌӃӃ ŀĸĺĴŊĴŇŇ ĸĿĸĶŇŅļĶ Ҏ ĸҏ ŅĸĴĶŇłŅņё ĹłŅ ŊĻļĶĻ ŇĻĸ ŅĸĴŇļłŁ Authorisation Decrees (DAC) authorise the use of plutonium fuel. ĻĴņ ņŇĴŁķĴŅķļņĸķ ĻłŊ ŇĻĸ ĹňĸĿ ļņ ňņĸķ ļŁ ļŇņ ŅĸĴĶŇłŅņё ŅĸĹĸŅŅĸķ Ňł Ĵņ ѢĹňĸĿ ŀĴŁĴĺĸŀĸŁŇѣѡє ňĸĿ ŀĴŁĴĺĸŀĸŁŇё ŊĻļĶĻ ĶłŁĶĸŅŁņ similar reactors, is more particularly characterised by: Ҋ the nature of the fuel and its initial fissile material content; Ҋ the maximum burnup of the fuel when removed from the reactor, characterising the quantity of energy extracted per ton of material, expressed in gigawatt days per tonne (GWd/t); Ҋ the duration of a reactor operating cycle; Ҋ the number of new fuel assemblies loaded following each reactor refuelling outage (generally one third or one quarter of the total number of assemblies). CONVENTIONAL ISLAND WP EAS RCV NUCLEAR ISLAND Moisture separator- Superheater Condenser Generator Secondary system Steam generator Vessel Control room Primary system RRA Fuel pool ARE TEP LP Turbine LP Turbine Turbine HP RIS RRI SEC RIVER Primary Pressurizer pump ASG PTR Heater ARE: Feedwater Flow Control System ASG: Auxiliary Feedwater System EAS: Containment Spray System PTR: Reactor Cavity and Spent Fuel Pit Cooling and Treatment System RCV: Chemical and Volume Control System RIS: Safety Injection System RRA: Residual Heat Removal System RRI: Component Cooling System SEC: Essential Service Water System (ESWS) TEP: Boron Recycle System LP or HP Turbine: Low pressure or high pressure VVP: Main Steam System Pressurised water reactor operating principle ASN Report on the state of nuclear safety and radiation protection in France in 2019 279 ׏׎ ٲ THE EDF NUCLEAR POWER PLANTS 10