GLOSSARY Active institutional controls: depending on the final state reached on a site, active institutional controls may be implemented to take account of the planned subsequent uses of the site and buildings. These can contain a number of restrictions on use (industrial use only, for example) or precautionary measures (radiological measures in the event of excavation, etc.). ASN may make the application of such institutional con-trols a pre-condition for delicensing a BNI*. ALARA (As Low As Reasonably Achievable): protection optimisation principle, the end-purpose of which is to reduce exposure to the ionising radiation received by each individual to a level that it as low as reasonably achievable, taking account of technical and economic constraints. Alpha particles: alpha particles are easily absorbed by matter but can only travel a few centimetres through air. They can be stopped by a sheet of paper or by the outer part of the skin and are therefore not generally considered dangerous to health – unless the source is inhaled or ingested. BNI: Basic Nuclear Installation. Installation which, due to its nature or the quantity or activity of the radioactive substances it contains, is governed by a particular regulatory system, defined by the Environment Code and the Order of 7 February 2012. Complex project: a project which involves a large number of interdependent elements which can interact at the same time and lead to unpredictable results liable to seriously impact the objectives of the project. Conversion: range of chemical transformations used to obtain uranium hexafluoride (UF6) from uranium ore, with a view to its enrichment, its storage, or the fabrication of nuclear fuel. Delicensing: consists in removing an installation from the BNI list, which implies that the installation is no longer subject to the BNI legal and administrative system. Diffuser cascade: range of large equipment items and piping which represent the heart of the gaseous diffusion process used to enrich uranium with isotope 235. Dispersible radiological inventory: the quantity of radio– active substances that could be involved in an incident or accident. Enrichment: process whereby the fissile isotopes content of an element is increased. The process leads to the separation of the product into two parts, referred to as “enriched” and “depleted” respectively in terms of the particular isotope. The enrichment of uranium with isotope 235 (235U) aims to make it usable as a fuel in the NPPs. Thus, the uranium which, its natural state, consists of 0.7% uranium-235, 235U (fissile) and 99.3% uranium-238, 238U (non-fissile) is enriched with uranium-235, the proportion of which will then be increased to about 3 to 4%. Excavation: the intentional extraction of soil in order to conduct works on the land (for example, digging the foundations of a construction). ICPE: Installation Classified for Protection of the Environment. Owing to its potential impact on the public and the environment, an in-stallation subject to the regulations defined in Title I of Book V of the Environment Code. “In air” (dismantling): As opposed to “under water” dis– mantling, this involves dismantling operations performed directly in the ambient air, with no water to limit the dispersal of contamination or attenuate the dose rate. “In water” (dismantling): mechanical cutting technique guaranteeing worker radiation protection and visibility during the operations. Sealed radioactive sources: Source for which the structure or packaging prevents all dispersion of radioactive substances into the ambient environment, in normal use. Shielded line: radiation protection device used for remote handling of radioactive or chemical products. Uranium hexafluoride – UF6: the uranium contained in nuclear fuels must be enriched with fissile isotope 235. Before being enriched, the uranium is first of all converted into a gas called “uranium hexafluoride”. WRC: retrieval and conditioning of legacy waste. This operation consists in retrieving legacy waste, stored in bulk, or in old and even damaged packages, and in reconditioning it in waste packages compliant with current safety standards. For example, this waste can be non-reusable substances from spent fuels from gas-cooled, light-water reactors (fission products and metal structures of spent fuels), as well as waste generated by the use of reprocessing processes (solvents, effluent treatment residues, ion exchange resins, etc.). 30 • Les cahiers de l’ASN • June 2022
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