ASN Report 2020

Decommissioning of Pressurised Water Reactors Considerable experience feedback from the decommissioning of Pressurised Water Reactors (PWRs) has been acquired through numerous projects internationally: 42 PWRs are currently undergoing decommissioning across the globe, and 6 have already been decommissioned in the United States. Furthermore, the design of these reactors facilitates their decommissioning compared with other reactor technologies, such as the first-generation Gas-Cooled Reactors (GCRs). The decommissioning of PWR facilities presents no major technical challenges and its feasibility is guaranteed: according to international experience feedback, the decommissioning of these reactors takes about 20 years. The PWR nuclear island is made up of three main buildings (see chapter 10, part 1): the reactor building, the fuel building and the nuclear auxiliaries building, housing the effluent treatment, ventilation and air filtration facilities. The conventional island for its part comprises a turbine hall housing the alternator that produces electricity. Decommissioning of the nuclear facilities is preceded by a phase of Decommissioning Preparation Operations (OPDEM). For a PWR, the main operation during this preparatory phase consists in unloading the fuel from the core, after which it will be stored in the spent fuel pool, then transferred from the facility to – in the case of France – the La Hague site for reprocessing (see chapter 11). The fuel represents the great majority of the radioactivity in the facility (approximately 95%): its removal therefore results in a significant reduction in the radiological risk. The residual radioactivity is then found chiefly in the primary system. For the decommissioning of the Fessenheim Nuclear Power Plant (NPP) whose, two reactors were definitively shut down in 2020 (see box in the Regional Overview in the introduction to this report – Grand Est region), EDF envisages decontaminating this system during the OPDEM with the aim of reducing radiological exposure during decommissioning. The decommissioning preparation phase will also include transforming the turbine hall into a waste treatment, packaging and storage facility. The decommissioning operations will start after the publishing of the Decommissioning Decree which defines the main steps of the facility decommissioning process. Decommissioning of the reactor building begins with removal of the primary system, followed by decommissioning of the reactor pressure vessel. The systems of the other buildings of the nuclear island are also decommissioned at the same time. Once of the equipment has been decommissioned and the waste removed, the licensee proceeds with the post-operational clean-out of the various buildings, followed by their demolition with a view to delicensing the Basic Nuclear Installation (BNI) and rehabilitating the site. In France, EDF is the sole licensee of the existing PWRs. Their decommissioning began in 2007 with the Chooz-A reactor, a limited power PWR situated in an excavated cavern. Whatever the service life of the reactors in operation, EDF will 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 shortest time possible. Decommissioning of the Fessenheim NPP will provide useful feedback in this respect. 1 - R e m o v a l o f t h e f u e l 2 - D e c o n t a m i n a t i o n o f t h e p r i m a r y s y s t e m 3 - D i s m a n t l i n g a n d r e m o v a l o f t h e c o n t a m i n a t e d a n d a c t i v a t e d c o m p o n e n t s 4 - C l e a n - o u t o f t h e b u i l d i n g 5 - R e m e d i a t i o n o f t h e s o i l s * * If necessary, the building is demolished in order to clean up the ground beneath the structures 344 ASN Report on the state of nuclear safety and radiation protection in France in 2020 13 – DECOMMISSIONING OF BASIC NUCLEAR INSTALLATIONS