- 63 - scenario does not lead to environmental releases. After a few tens of hours, it would lead to the UF6 solidifying in the diffusers, a process that would probably be irreversible. For the GB II plant, as the loss of electrical power supplies would not represent a safety issue for the facility, they are not designed to comply with seismic standards. There are backup resources but not all the operating procedures have yet been drafted. The inspectors' comments primarily concerned the inspections, periodic tests, maintenance, and operating procedures for these resources. In several facilities at Tricastin, an interruption of the ventilation after an earthquake, owing to an intentional or otherwise break in the electrical power supplies, can halt measurement of release activity or lead to loss of the environmental monitoring systems. For Eurodif, monitoring to ensure that there are no leaks of chlorine trifluoride (ClF3) is carried out by a patrol every two hours: this point is not included in an operating document. A check-list of the operations to be performed is currently being drafted. To conclude, the subject of electrical power supplies is dealt with on the whole satisfactorily, in accordance with the safety frame of reference in force. The safety issues related to the loss of electrical power supplies alone are minor for the facilities on the Tricastin platform. Consequently, the design of the normal or backup electrical power supplies, their monitoring, their periodic testing and their maintenance are thus appropriate for equipment not classified as "elements important for safety" (EIS). However, in a number of facilities, the loss of electrical power leads in the medium term to the loss of the means of monitoring the facility from the control room and a loss of the means of communication. Managing an accident situation at the same time as this loss of electrical power would thus be relatively problematical. Therefore, the checks, in particular the second-level checks on the backup power supply resources, for instance the UPS systems and batteries, need to be strengthened, to ensure that they are available and that they would function for long enough if the electrical power supplies were to be lost. Nuclear fuel fabrication facilities (Mélox, FBFC) Mélox The immediate or eventual consequences of the loss of electrical power are shutdown of the production equipment or the equipment driven by a drive fluid, plus the loss of cooling, reheating and inerting functions. The nature of the corresponding risks thus varies with the nature and function of the workstations, with issues in terms of confinement, radiation protection, criticality, release of heat, fire, onsite or off-site flooding, handling and explosion. Electrical energy can be supplied by a cascade of different sources, thus enhancing the operating reliability of the equipment contributing to the safety of the facility. A general agreement signed with CEA in March 2010 specifies the property limits and the operating perimeter. The inspectors noted that EDF/normal backed-up "switchover" at equivalent power and redundancy, gives the Mélox plant a degree of independence. The Mélox plant is relatively self-sufficient. A permanent EDF supply is not therefore essential, as the two GEF which take part in the "normal/backed-up" layer can for 48 hours provide power equivalent to that of the EDF lines, with the same degree of redundancy. The alarms are transmitted to the PSG and to the safeguard command posts. The inspectors found that: an inventory of the elements to be safeguarded was drawn up (loss of normal and backup EDF supplies and loss of backup generator sets); the safeguard generators have self-sufficiency of one week (limited to 48h for the GEF handling normal backed-up) determined solely on the basis of the capacity (60 m3) of the fuel reserve (with no outside resupply). The tanks are designed to withstand the site's reference earthquake; radiation protection monitoring and the criticality detection and alarm systems (EDAC) are not safeguarded;
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