Architecture and management of a geological repository - Andra

11 – Operational SafetyOn the surface, the transport transfer cask vehicle leaves the waste reception area as soon as thetransfer cask has been set down which limits the presence of the main cause of the risk. Furthermore,the transport transfer cask is designed to resist fire up to 800°C for 30 minutes in accordance withtransport regulations [110].In underground facilities, there is no industrial reference directly applicable to the transfer vehicle aswell as to the B waste emplacement equipment. It has therefore been necessary to make simulations onthe basis of assumptions regarding the heat ratings involved and the nature of the exchanges in thecourse of the fire. These studies are presented in Sections 11.5 (Transfer transfer cask transporter) and11.6 (B Waste emplacement handling equipment).• Primary package falling in surface nuclear installationsPrimary packages could be dropped and damaged during handling. The foreseeable consequences ofthis could be a breach of one or more of the primary packages and the dispersion of radioactivematerial in the installations and subsequently into the environment via the ventilation. A fall could alsoresult in the surface contamination of a package missed during other inspections becoming airborne(cf. 11.1.1.4).Preventive measures are specific to each type of equipment. Equipment systems must be sized forloads greater than those envisaged, must ensure a degree of redundancy in some components andintrinsically safe devices must be designed for the possibility of malfunction (for example, keeping thegrab closed in the event of a power failure). Training of personnel and maintenance are also veryimportant in countering this risk. In addition, the mechanical procedure used must give priority tohandling packages at a height lower than the height from which they are known to withstand beingdropped.As the protective measure to be used to take care of a potential release of radioactive materials, afiltered ventilation system could be installed on the ventilation circuit of the primary packagereception and disposal package manufacturing cells.This measure might be justified for some primary B waste packages, such as the bituminised sludgepackage, which is not totally protected from the possibility of the crimping of its lid failing andopening in the event of impact.This measure would also apply to installations receiveing bare spent fuel assemblies which, if droppedduring the handling operations that are necessary until they are placed in disposal packages, couldresult in the rupture of the cladding of the fuel rods. The main provisions for the management of thistype of risk could be similar to those used for the dry unloading of this type of fuel in the reprocessingplant (Cogema T0 facility in La Hague).• B Waste disposal package drop during emplacement 157Carring the waste disposal package in the low position over the whole length of the disposal cell limitsthe risk of it falling during the package lifting and emplacement. During this operation, an error in thepositionning of the expected position of the package to be emplaced, or the malfunction of the liftingsystem, could result in a fall from a height of 4 to 6 m in the case of packages placed on the highestlevels of the stacks.Several provisions are envisaged to limit the occurrence of this risk and its consequences:- The emplacement procedure with a row of waste disposal packages placed on the ground followedby a second layer and so forth limits the risk to a case in which a package might tip on its side;- Monitoring the package emplacement cycle (validated step by step by the operator, visualinspection using cameras) and checking that the emplacement position matches the cell mapbeforehand should prevent any error in positioning when the package is being set down;157 The procedures envisaged for emplacement in the cell of C and SF packages (cf. Section 9.3) require a handling height of less than2 meters. Because of this, these drop cases are not dealt with.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM447/495