Abstracts ASN Report 2019

׫٫ ڲ Situation of nuclear facilities undergoing decommissioning – specific challenges Ň ŇĻĸ ĸŁķ łĹ ӅӃӄӌё ӆӈׇŁňĶĿĸĴŅ ĹĴĶļĿļŇļĸņ ļŁ ŅĴŁĶĸ ĴŅĸ ķĸĹļŁļŇļʼnĸĿŌ shut down or undergoing decommissioning. It is planned to shut down some ten more facilities in the coming years (see map below). These facilities are varied (nuclear power reactors, research reactors, fuel cycle facilities, support facilities, etc.) and the decommissioning challenges can differ greatly from one facility to the next. These challenges are, however, all linked to the large quantity of waste to be managed during decommissioning. The risks for safety and radiation protection are all the higher if the facilities contain legacy waste; this is the case with the Orano Cycle former spent fuel reprocessing plants or the CEA’s old storage facilities. א ِ׏ zɖƬǼƺƏȸ ȵȒɯƺȸ ȸƺƏƬɎȒȸɀ א ِ׏ِ׏ ¨ȸƺɀɀɖȸǣɀƺƳ áƏɎƺȸ ȇɖƬǼƺƏȸ ȵȒɯƺȸ «ƺƏƬɎȒȸɀ The first Pressurised Water Reactor (PWR) undergoing decom- ŀļņņļłŁļŁĺ ļŁ ŅĴŁĶĸ ļņ ŇĻĸ Ļłłō ŅĸĴĶŇłŅ Ҏ ׇӄӉӆҏє Ļļņ ļņ Ĵ ņŀĴĿĿ ŀłķĸĿ ĶłŀŃĴŅĸķ ŊļŇĻ ŇĻĸ ӈӋׇŁňĶĿĸĴŅ ŃłŊĸŅ ŅĸĴĶŇłŅņ ļŁ łŃĸŅĴŇļłŁє ĸĶłŀŀļņņļłŁļŁĺ łĹ Ļłłō ĻĴņ ĵĸĸŁ ĴňŇĻłŅļņĸķ ĵŌ ĸĶŅĸĸ ņļŁĶĸ ӅӃӃӊׇĴŁķ ŃŅĸņĸŁŇņ ņłŀĸ ņŃĸĶļĹļĶ ŇĸĶĻŁļĶĴĿ difficulties due to its construction inside a cavern. This makes some operations more complex, such as the removal of large components like the steam generators. Decommissioning of the Ļłłō ŅĸĴĶŇłŅ ʼnĸņņĸĿ ĴŁķ ļŇņ ļŁŇĸŅŁĴĿ ĶłŀŃłŁĸŁŇņ ļņ ļŁ ŃŅłĺŅĸņņ and should continue in the timeframes specified in the Decree. PWR decommissioning benefits from experience feedback from numerous projects across the world and the design of these reactors facilitates their decommissioning compared with other reactor technologies. The decommissioning of this type of installation presents no major technical challenges and its feasibility is guaranteed. ĻĴŇĸʼnĸŅ ŇĻĸ ņĸŅʼnļĶĸ ĿļĹĸ łĹ ŇĻĸ ŅĸĴĶŇłŅņ ļŁ łŃĸŅĴŇļłŁņё ŊļĿĿ be confronted with the simultaneous decommissioning of several PWRs in the coming years and will therefore have to organise itself to industrialise the decommissioning process in order to meet the requirement to decommission each installation in the ņĻłŅŇĸņŇ Ňļŀĸ ŃłņņļĵĿĸє Ļĸ ĹļŁĴĿ ņĻňŇķłŊŁ łĹ ŇĻĸ ĸņņĸŁĻĸļŀ Nuclear Power Plant (NPP) is planned for 2020. This will be the ĹļŅņŇ łĹ ŇĻĸ ӈӋׇ ņ ĶňŅŅĸŁŇĿŌ ļŁ łŃĸŅĴŇļłŁ Ňł ĵĸ ķĸĶłŀŀļņņļłŁĸķ ļŁ ŅĴŁĶĸє Ļĸ ķĸĶłŀŀļņņļłŁļŁĺ łĹ ĸņņĸŁĻĸļŀ ŊļĿĿ ŇĻňņ ŃŅłʼnļķĸ ŊļŇĻ ĶłŁņļķĸŅĴĵĿĸ ĸŋŃĸŅļĸŁĶĸ ĹĸĸķĵĴĶľ ĹłŅ ŇĻĸ łŇĻĸŅ ņє א ِ׏ِ א zɖƬǼƺƏȸ ȵȒɯƺȸ ȸƺƏƬɎȒȸɀ ȒɎǝƺȸ ɎǝƏȇ ¨á«ɀ The nuclear power reactors that are not PWRs are all industrial prototypes. These comprise the first-generation Gas-Cooled Reactors (GCRs), the EL4-D heavy water reactor on the Brennilis site, and the sodium-cooled fast breeder reactors Phénix and Superphénix. Some of these reactors have been shut down for several decades, which has led to loss of knowledge of the installation and its operation and loss of the skills associated with these reactors. Ļĸ ķĸĶłŀŀļņņļłŁļŁĺ łĹ ŇĻĸņĸ ŅĸĴĶŇłŅņ ļņ ĶĻĴŅĴĶŇĸŅļōĸķ ĵŌ ŇĻĸ lack of prior national or international experience. As with the PWRs, decommissioning begins with the removal of ŇĻĸ ŁňĶĿĸĴŅ ĹňĸĿё ŊĻļĶĻ Ņĸŀłʼnĸņ ӌӌՌ łĹ ŇĻĸ ŅĴķļłĴĶŇļʼnļŇŌ ŃŅĸņĸŁŇ in the installation. As the thermal power of these reactors is ŅĸĿĴŇļʼnĸĿŌ ĻļĺĻ ҂ĴĿĿ ĺŅĸĴŇĸŅ ŇĻĴŁ ӅӈӃׇ ŇĻ ҎŀĸĺĴŊĴŇŇņ ŇĻĸŅŀĴĿҏё their decommissioning necessitates the cutting away and removal of the activated parts of the reactor core. Remotely-operated ŀĸĴŁņ ĴŅĸ ŇĻĸŅĸĹłŅĸ ňņĸķ ļŁ ŇĻĸņĸ ĻļĺĻĿŌ ļŅŅĴķļĴŇļŁĺ ōłŁĸņє ŁׇʼnļĸŊ of their unique nature, specific and complex operations have to be devised and carried out to decommission them. The GCRs have the particularity of being extremely massive ĴŁķ ĿĴŅĺĸіņļōĸķ ŅĸĴĶŇłŅņё ŁĸĶĸņņļŇĴŇļŁĺ ļŁŁłʼnĴŇļʼnĸ ĶňŇŇļŁĺ ĴŁķ access techniques under highly irradiating conditions. The ķĸĶłŀŀļņņļłŁļŁĺ łĹ ŇĻĸņĸ ŅĸĴĶŇłŅņ ŊļĿĿ łĵĿļĺĸ Ňł ŀĴŁĴĺĸ significant volumes of waste. The final disposal route for some of this waste is in the process of being determined, such as the graphite bricks, for which low-level, long lived waste (LLW-LL) disposal is envisaged. Decommissioning of the EL4-D reactor (prototype heavy water reactor) has been slowed, firstly due to the lack of prior experience in the decommissioning techniques to be used, and secondly due to unforeseen setbacks concerning the conditioning and storage facility for activated waste (Iceda, see introductory section and chapter 14). The decommissioning of the sodium-cooled reactors (Phénix and Superphénix) has met with no major technological obstacles. The specific challenges lie chiefly in the control of the fire risk due to the presence of sodium and the safety of its treatment processes. א ِ א «ƺɀƺƏȸƬǝ ǔƏƬǣǼǣɎǣƺɀ א ِ א ِ׏ «ƺɀƺƏȸƬǝ ǼƏƫȒȸƏɎȒȸǣƺɀ łňŅ ŅĸņĸĴŅĶĻ ĿĴĵłŅĴŇłŅļĸņ ĴŅĸ ĶňŅŅĸŁŇĿŌ ňŁķĸŅĺłļŁĺ decommissioning or preparation for decommissioning. These ĴŅĸ ŇĻĸ ļĺĻ ĶŇļʼnļŇŌ ĴĵłŅĴŇłŅŌ Ҏ ҏ ĴŇ ĴĶĿĴŌ Ҏ ׇӇӌҏё ŇĻĸ ĻĸŀļĶĴĿ ňŅļĹļĶĴŇļłŁ ĴĵłŅĴŇłŅŌ Ҏ ҏ ĴŇ ĴķĴŅĴĶĻĸ Ҏ ׇӈӇҏё ŇĻĸ ŅŅĴķļĴŇĸķ ĴŇĸŅļĴĿņ ĿĴŁŇ Ҏ ҏ ĴŇ ĻļŁłŁ Ҏ ׇӌӇҏ ĴŁķ ŇĻĸ Ѣ ŅłĶĸņņѣ ĿĴĵłŅĴŇłŅŌ ĴŇ łŁŇĸŁĴŌіĴňŋі łņĸņ Ҏ ׇӄӉӈҏє Ļĸņĸ ĿĴĵłŅĴŇłŅļĸņё ŊĻļĶĻ ĵĸĺĴŁ łŃĸŅĴŇļŁĺ ļŁ ŇĻĸ ӄӌӉӃņё ŊĸŅĸ ķĸķļĶĴŇĸķ to Research & Development to support the development of the ŁňĶĿĸĴŅ ŃłŊĸŅ ļŁķňņŇŅŌ ļŁ ŅĴŁĶĸє Research laboratory decommissioning operations prior to delicensing are typically carried out in several steps: Ҋ removal of the legacy or old waste; Ҋ disassembly of the electromechanical equipment and the reactor containments; Ҋ cleaning out of the structures and remediation of the soils polluted by the activities of the BNI, if necessary. Dismantling of the structures and civil engineering work, if applicable, can be carried out in the conventional manner after their complete clean-out. Nevertheless, in certain cases of highly contaminated structures, dismantling must be carried out during the decommissioning steps as their stability cannot be guaranteed once they have been cleaned out. In such cases, dismantling, which is carried out using techniques specific to the nuclear industry, is a step necessary for delicensing. These very old facilities are all confronted with the issue of managing the “legacy” waste, stored on-site at a time when the waste management routes had not been put in place: intermediate level, long-lived waste (ILW-LL) and waste without a disposal route (e.g. asbestos, mercury, etc.). Moreover, incidents occurred during their operation, contributing to the emission of radioactive substances inside and outside the containment enclosures and to the varying levels of pollution of the structures and soils, making the decommissioning operations long and difficult. One of the most important steps in the decommissioning of this type of facility, and which is sometimes rendered difficult due to incomplete archives, consists in inventorying the waste and the radiological status of the facility as accurately as possible ASN Report on the state of nuclear safety and radiation protection in France in 2019 335 ׏ ٲ ב DECOMMISSIONING OF BASIC NUCLEAR INSTALLATIONS 13