02 03 04 05 06 07 08 09 10 11 12 13 01 In 2024, 36 nuclear installations of all types (power and research reactors, laboratories, fuel reprocessing plants, waste treatment facilities, etc.) were shut down or are undergoing decommissioning in France, representing more than one quarter of the Basic Nuclear Installations (BNIs) in operation. With the exception of the Pressurised Water Reactors (PWRs) in the Nuclear Power Plants (NPPs), whose design follows a generic model, the majority of the BNIs being decommissioned present varied technologies, uses and operating histories, rendering complex the decommissioning operations. The duration of BNI decommissioning operations can thus vary significantly from one facility to another. The French Nuclear Safety Authority (ASN) notes that if it takes about twenty years to decommission the PWRs, decommissioning may extend well beyond 2050 for some of the “fuel cycle” facilities or old waste storage facilities, as several of them still contain large quantities of waste to be retrieved and conditioned. For these facilities, new equipment and processes have to be developed and built, leading to long and complex decommissioning operations. ASN thus notes that the schedules established by the licensees in the years 2000 with a view to issuing the first decommissioning decrees are having to be updated to integrate the lessons learned from the first operations and to introduce more realistic operational margins, thereby pushing back the end-of-decommissioning dates much further. ASN is vigilant regarding the safety risks linked to significant extensions of decommissioning times. 1 Technical and legal framework for decommissioning The term decommissioning covers all the technical and administrative activities carried out after the final shutdown of a nuclear installation, following which it can be delicensed, in other words removed from the list of BNIs. These activities comprise the removal of radioactive materials and waste still present in the facility and operations to dismantle the equipment and components used during operation, as well as clean-out of the premises and soils plus civil engineering structures demolition work as necessary. The aim of the decommissioning and clean-out operations is to achieve a predetermined final state that allows prevention of the risks and impacts that the site may present for the environment and people, taking into account its possible future uses. The decommissioning of a nuclear installation is prescribed by Decree issued after consulting ASN. This phase in the life cycle of the installations is characterised by a succession of operations which are sometimes highly complex, are lengthy, produce large amounts of waste, and are costly; optimum forward planning is essential – especially given that they must be carried out within the shortest time frame possible, as stipulated in the regulations. The continuous changes that installations undergo in the course of decommissioning alter the nature of the risks and represent challenges for the licensees in terms of project management. 1.1 Decommissioning challenges Accomplishing the decommissioning operations – which are often long and costly – within the set time frames is a challenge for the licensees in terms of project management, skills maintenance and coordination of the various operations which involve numerous specialist companies. Despite this, the principle of immediate dismantling in France obliges the licensees to carry out their decommissioning operations within the shortest time frame possible under economically acceptable conditions (see point 1.2). Decommissioning comprises a series of operations which tend to gradually reduce the quantity of radioactive substances present in the facility, resulting in evolving risk levels. Although the reduction in the quantities of substances present in the facility tends to reduce the risks, the decommissioning work, which sometimes takes place very close to the radioactive substances, nevertheless presents significant radiation exposure risks for the workers. Other risks also increase as the work proceeds, such as the risk of dispersion of radioactive substances into the environment or certain conventional risks, such as risks of falling loads when handling large components, or of fires during hot work in the presence of combustible materials, instability of partially dismantled structures, or chemical risks during decontamination operations. One of the major challenges in the decommissioning of an installation is linked to the large volumes of waste produced, which are usually very much greater than the volumes produced during its operation. The decommissioning of the former facilities of the Alternative Energies and Atomic Energy Agency (CEA) and Orano’s first generation plants (in particular the plants which were involved in France’s deterrence policy, such as the gaseous diffusion facilities of the Pierrelatte Defence Basic Nuclear Installation (DBNI – defence sector) in Tricastin, and the UP1 facility at the Marcoule DBNI, will thus lead to the production of a very large quantity of very low-level (VLL) waste). The scale and the difficulty of the work must be assessed as early as possible in the life of the installation, and as of the design stage for new facilities, in order to ensure that they can be decommissioned safely within as short a time frame as possible. Furthermore, radioactive substances are still present in some old installations, sometimes in large quantities; these substances are not always readily accessible and some of them remain to be characterized. The conditions of retrieving and conditioning these substances in such cases constitute projects in their own right within the decommissioning projects. This is the case in particular with the former effluent treatment facilities of CEA and Orano (see chapter 15). ASN Report on the state of nuclear safety and radiation protection in France in 2024 353 Decommissioning of Basic Nuclear Installations 14 15 AP
RkJQdWJsaXNoZXIy NjQ0NzU=