Architecture and management of a geological repository - Andra

11 – Operational SafetyAs for any other industrial facility, the various disposal activities (construction, operation and closure)can present a risk to personnel, members of the public and the environment.This chapter presents a preliminary operational safety analysis on the basis of the current levelknowledge of the disposal facilities and takes into account the experience of other comparablefacilities. This analysis makes it possible to ensure that risks are brought under control throughprovisions in the design of the repository and operation in compliance with safety functions 146 definedby Andra.Within the context of this analysis, a preliminary evaluation of the dosimetry with the installations inoperation is presented.A summary of the risk analysis is also set forth. It highlights certain particular risks for whichadditional studies have been carried out on account of their specific characteristics or their impact onthe design of the repository and its equipment.This chapter goes on to offer an analysis of the particular abovementioned risks, namely, the risk ofexplosion associated with the emission of gas by certain waste packages, the risk of fire breaking outin underground installations under construction and in operation, the risk of a cage falling down thepackage descent shaft during transfer operations and the risk of a B waste package falling during itsemplacement in a cell. Finally, a summary of the analysis is given by way of conclusion.11.1 Evaluation of the dosimetry with the installations in operationThe operation of the facilities in which nuclear waste is received, conditioned, handled and disposedpresents radiological risks to persons on account of the nature of the waste packages. There are severaltypes of risk: the risk of external exposure (by irradiation) and the risk of internal exposure (byinhalation or ingestion).This section presents a preliminary assessment of the dosimetry that takes into account the preventivemeasures envisaged to counter the radiological risks. These measures must ensure exposure of personsdoes not exceed the annual dose rate constraints set by Andra in the form of radiological protectiontargets of 5 mSv for personnel working in the nuclear zone and 0.25 mSv for members of the publicoutside the site [37].This dosimetry evaluation informs the approach to the design of these installations from the point ofview of radiological risk but is not, at this stage, part of an approach to optimise the doses received.11.1.1 The nature of radiological risks and measures envisagedThe various radiological risks that affect the facilities are set forth in the following sections.11.1.1.1 External exposure riskWaste packages are sources of external exposure (associated with β, γ and neutron radiation) from themoment they are received in the surface installations until they are placed in the underground disposalfacilities.146 The safety functions defined (cf. Section 2.4) are as follows:- Protection of persons from radiation,- Containment of radioactivity,- Control of the criticality risk,- Removal of residual heat of disposal packages,- Removal of the radyolisis gases emitted by some packages.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM436/495