ASN Report 2018

2.2  ̶  Research facilities 2.2.1  –  Research laboratories Four research laboratories are currently undergoing decommissioning or preparation for decommissioning. These are the High Activity Laboratory (LHA) at Saclay (BNI 49), the Chemical Purification Laboratory (LPC) at Cadarache (BNI 54), the Irradiated Materials Plant (AMI) at Chinon (BNI 94) and the “Process” laboratory at Fontenay-aux-Roses (BNI 165). These laboratories, which began operating in the 1960’s, were dedicated to R&D to support the nuclear power industry in France. Research laboratory decommissioning operations prior to delicensing are typically carried out in several steps: ∙ ∙ removal of the legacy or old waste; ∙ ∙ disassembly of the electromechanical equipment and the reactor containments; ∙ ∙ 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, such as 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 as accurately as possible the waste and the radiological status of the facility in order to define the decommissioning steps and the waste management routes. This is because incomplete understanding of the initial situations and insufficient characterisation of the waste make it necessary to revise the planned steps and lead to difficulties in packaging the waste, which is counterproductive to decommissioning progress. When the waste is removed, very often to interim storage areas, and the main equipment remotely dismantled using the existing handling means, continuation of the decommissioning work usually necessitates opening the radioactive substance containment barriers in order to remove the last process or research equipment and the pipes using, among other things, more substantial cutting and handling equipment. The latter present risks in themselves and can lead to dissemination of radioactive material, a potential source of internal and external contamination for the operators who work at close range and must be protected. This work can moreover be carried out near radiation sources, which increases the risk of external exposure for the workers. 2.2.2  –  Research reactors Six experimental reactors are in definitive shut down status in 2018: Rapsodie (sodium-cooled fast neutron reactor), Masurca (critical mock-up), Minerve, Phébus, Osiris (“pool” type reactors), ÉOLE (water reactor) and Ulysse (training reactor). They are all in the decommissioning preparation phase, except for Ulysse, whose decommissioning is to be completed in 2019. These reactors are characterised by a lower power output (from 100 Wth to 70 MWth) than the nuclear power reactors. When they were designed back in the 1960’s to 1980’s, the question of their decommissioning was not considered. One of the major decommissioning problems is the loss of memory of the design and operation of the installation. Thus, the maintaining of skills and the installation characterisation phase to determine its initial state (state of the installation at the start of decommissioning) are of vital importance. At the time of decommissioning, these installations usually present a low radiological source term as one of the first operations consists in removing the spent fuel during the decommissioning preparation operations. There is a considerable amount of decommissioning experience feedback for the research reactors, given the decommissioning of numerous similar installations in France (Siloé, Siloette, Harmonie, Triton, the Strasbourg university reactor) and abroad. Their dismantling time frames span about ten years. The risks involved in research reactor decommissioning operations evolve rapidly due to the numerous changes in the installation. The nuclear risks gradually give way to conventional industrial risks, such as the risk associated with the simultaneous management of several worksites, or the chemical risk during the clean-out phase. One of the main challenges comes from the production and management of large volumes of very low-level waste, which must be stored then disposed of via an appropriate route. 2.3  ̶  The front-end nuclear fuel cycle facilities Four front-end nuclear fuel cycle facilities are in shutdown status. Two facilities (BNI 65 and 90), whose decommissioning is almost complete, constitute the former nuclear fuel manufacturing plant of Veurey-Voroize, operated by the Société industrielle du combustible nucléaire (Orano group). Two facilities situated on the Tricastin site, one specialising in uranium enrichment by gaseous diffusion (BNI 93), the other in uranium conversion (BNI 105) are in the decommissioning preparation phase. The only radioactive materials used in these plants were uranium-bearing substances. One of the particularities of these facilities therefore lies in the presence of radioactive contamination associated with the presence of “alpha” ASN inspection at the AMI irradiated materials facility - June 2018 ASN report on the state of nuclear safety and radiation protection in France in 2018  341 13 – DECOMMISSIONING OF BASIC NUCLEAR INSTALLATIONS 13