Architecture and management of a geological repository - Andra

11 – Operational Safety11.2.2.2 Radiological risksRadiological risks (external exposure risks, internal exposure risk and potentially criticality risk) likelyto be encountered during the course of the disposal process could be associated with radiologicalprotection failures, interventions carried out close to a source of radioactivity or a fire or fall affectingwaste packages.Having taken account of their specific characteristics, these risks are analysed individually andemphasis is placed on measures to reduce the risks envisaged.• Failure of the radiological protection provided by the doors, vents and shieldedwindows of nuclear cells in surface installations, transfer transfer casks, accessports of the C and spent fuel disposal cells and doors of the B disposal cellsThese events could be the result, for example, of clearance between moving parts that is not compliantwith the initial dimensioning. Measures required to counter this risk would be a specific maintenanceprogramme for moving parts associated with radiation detection monitoring of the nuclear cells,transfer transfer casks and disposal cells.• Failure of radiological protection during the course of an interventionEquipment malfunction may lead to its immobilisation when being used to carry or handle a package(primary package or disposal package) and intervention by maintenance personnel may be required torepair the equipment in question. This situation would result in the external exposure of personnel ifthe latter had to operate near the source of radiation.Preventive measures would be those conventionally used in nuclear facilities currently in operation,namely, appropriate maintenance of the equipment used and redundancy of certain component parts(motorisation, etc.).Where intervention carried out on equipment in cells is concerned, the existence of emergencysystems enabling the waste package to be put down and the equipment returned unloaded to itsmaintenance area would remove all risk of the exposure of personnel. In the latter case, it would,however, be necessary to ensure there is no malfunction of the closure system of the irradiating zoneof the cell 156 by first monitoring the level of radiation in the maintenance area prior to any operation.• Fire in a nuclear cell of the surface installationsA fire in the disposal package manufacturing cell would have a fairly insignificant heat rating giventhe low calorific load of the equipment installed.Taking feedback from the experience of nuclear facilities into account in the design of installations,limiting the calorific loads present and possibly installing thermal protections around some equipmentshould be sufficient to limit the power of a fire and prevent it from spreading and affecting thepackages resulting in radiological consequences.• Waste transportation or handling vehicle fireThe fire of a transport transfer cask vehicle (containing primary packages from waste producers), atransfer transfer cask vehicle (containing waste disposal packages) or B waste emplacement equipmentin the disposal cell could have radiological consequences in addition to the direct consequences of thefire (cf. Section 11.4).156 The system usually employed consists of locking in the opening of the maintenance area with the closure of the irradiating cell and, ifpossible, locating the maintenance area at some distance from a potential field of radiation from the sources of radioactivity present inthe cell.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM446/495