- 150 - The arrival of clogging agents in the pumping station is detected by the alarms specific to this system: monitoring of suction head loss, SEF alarms35, loss of head of the SFI36 filtration resources. The associated protection systems will automatically trip the pumps that are not safety-classified, thereby significantly reducing the head loss at the bounds of the filtering elements to guarantee their integrity and reduce the influx of debris. This system protects the ESWS system safety pumps against a low level at suction and ensures their lasting supply. Preventive measures that can be initiated manually from the control room and followed by local verifications, including the stopping of one or more non-safety-classified pumps and starting of highpressure washing and high-speed operation of the rotating drum filters. An operator will be sent to assess the situation; the operating teams have a specific procedures to guide the management of this situation . In response to a partial heat sink loss incident at the Cruas NPP in 2009 caused by a massive influx of vegetation debris, ASN asked EDF to undertake a design review of all the heat sinks to assess and reinforce their robustness to natural hazards. The results of this technical design review are expected in 2012. 5. To avoid heat sink loss due to natural phenomena (storms, spring tides, etc.) Some NPP sites manage these situations by a specific operating procedure that integrates the phenomena of storms with simultaneous presence of clogging agents that can affect the availability of the water intake. The aim of this procedure is to avoid total loss of the heat sink by maintaining the flow necessary for operation of the pumps that are important for safety, and facilitate the cleaning of clogged equipment. This procedure prescribes the monitoring of numerous parameters such as the pumping station alarms, the weather conditions - especially wind speed and direction, historical wind records, tidal conditions and sea state, the change in operation of the neighbouring plant unit CRF pumps, the nature of the clogging agent and the actions to implement. It also prescribes tightened monitoring of the pumping station and envisages several cases of plant unit shutdown. Each NPP site also establishes specific instructions, such as for lashing down objects in the event of high winds. ASN considers that the heat sink, which is an important system, requires particular vigilance. Its vulnerability was highlighted by the recent events of clogging and partial loss of the heat sink at Cruas and at Fessenheim in December 2009, which led EDF to initiate a plan of action to reinforce the robustness of all its heat sinks. ASN has more particularly asked EDF to conduct a design review of all its heat sinks. ASN will instruct EDF to provide detailed conclusions of the heat sink design review, site by site, along with a plan of action with completion dates. The inspections ASN carried out in 2011 found the general condition of the heat sink facilities to be satisfactory, and that almost all of them are in conformity with the EDF's national baseline safety standard, though there are still some deviations on a number of sites. As a general rule, operating and maintenance rigour, equipment and structure condition monitoring, and exhaustive application of national directives, are areas for improvement on most sites. Despite noteworthy progress attributable to the EDF's OEEI initiative (French acronym meaning "to achieve an exemplary condition in installations "), a number of sites still have pumping station equipment displaying leaks or relatively advanced corrosion. Several sites displayed shortcomings in the maintenance of the SEC system, which is classified for safety and therefore merits greater attention. The risk of heat sink loss (by clogging, freezing, etc.) is not addressed equally from one site to another, and generally requires greater attention. The recent events have shown that the means currently in place have been sufficient to cope with the hazards, though sometimes with difficulty. EDF has therefore started to reinforce the robustness of its heat sinks against the risk of "massive influx of clogging material." Personnel training has occasionally displayed deficiencies, making it a area for progress included in the plan of action implemented by EDF in 2010 in response to the heat sink clogging events at Cruas and Fessenheim. Lastly, EDF has planned to tighten the baseline safety standard for the heat sink, with early 2013 announced as the plan of action completion date. 35 SEF : raw water coarse filtration system (the first filtration of the water drawn from the natural environment 36 SFI : raw water filtering system (in the pumping station)
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