ASN Report 2018

2.4.2  –  Assessment of reactor operations • Normal and degraded operation In 2018, EDF encountered difficulties in controlling its operating and maintenance activities, notably in the restarts following reactor outages. ASN has not observed any significant improvement in the quality of NPP operations by comparison with 2017, in that the underlying causes of the faults appear to be structural and the effects of the steps taken by EDF are not yet measurable. The control of certain sensitive activities, such as temporary system configuration changes in order to carry out periodic tests on certain equipment, which is the origin of operating non-quality, would appear to be progressing on certain sites. This progress, which must be placed in the context of the action plans being run by EDF for several years now, still remains to be consolidated. However, alarms processing in the control room - from their acknowledgement by the operating team to the performance of the control actions required by the alarm sheets – is less satisfactory. ASN more particularly notes that the personnel become accustomed to recurring alarms, which is particularly prejudicial when a given alarm can indicate different failures. Maintenance quality defects are regularly the cause of an increase in the length of the restart phases following reactor refuelling outages. Recurring activities, such as periodic tests, were also the cause of deviations in the preparation and performance phases. The stakeholders concerned have insufficiently assimilated error-reduction practices for these interventions. As a result of this situation, ASN continued with the adapted oversight arrangements implemented in 2018. This more particularly leads to tightened inspections on the most under- performing sites. ASN also observes that the processes EDF implemented for the design of technical operating specifications and periodic test rules requiring its authorisation, were deficient on several occasions. More specifically, EDF was required to revise the general operating rules for the 1,300 MWe reactors applied following their third ten-yearly outage inspection to ensure that the actual state of the facilities was consistent with the operating documents. The tightened inspections performed by ASN in 2018, led EDF to initiate a profound overhaul of its design processes for the documentation used to ensure the maintained operation of the reactors within the scope covered by their nuclear safety case. The scheduling, performance and analysis of the results of periodic tests are areas in which virtually all the sites need to improve. This observation has been made repeatedly for numerous sites. The filled-out periodic test procedures are documents that are regularly inspected by the ASN inspectors. ASN observes that the lack of preparation for the periodic tests sometimes leads to the performance frequencies being exceeded and to inadequate conditions for performance of the tests. The other reason for the delays in performance of tests is the implementation of the new IT system in the NPPs, in which certain periodic tests were sometimes incorrectly transposed. Furthermore, ASN’s inspectors on several occasions found incorrect conclusions regarding equipment availability following periodic testing. ASN also observes that the sites experience difficulties in translating the requirements of the periodic test rules into actual test procedures. All of these situations have led to numerous significant safety events. A significant safety event concerning the lack of metrological monitoring of the sensors used to validate safety criteria during periodic tests notably attracted ASN’s attention and it ensured that the sites update the metrological monitoring of the sensors and are also able to demonstrate the availability of any equipment which was tested with sensors that were not monitored. ASN also found recurring monitoring faults during the core physics tests performed at reactor restart and during operation. These anomalies more particularly concern the rod control cluster drop time measurements and compromise the detection of possible deviations regarding reactivity control. Moreover, ASN considers that the analysis of early warning signs regarding the unavailability of equipment that would be needed during primary coolant dilution accidents needs to be reinforced. As in 2017, ASN in 2018 observes that the follow-up of the opinions expressed by the Independent Safety Organisation (FIS) in place within each EDF entity, varies significantly from one NPP to another. ASN more particularly found that the EDF decision-making process, which notably includes the FIS, does not always ensure that priority is given to the protection of interests. • Operation in an incident, accident, or severe accident situation In the same way as every year, ASN carried out several inspections in 2018 on the organisational and technical arrangements made by EDF to deal with an incident and accident situation. One of them was a reactive inspection following a severe pressure control malfunction on the reactor coolant system of Bugey NPP reactor 5. During these inspections, ASN on the one hand checks the way in which the operating procedures are applied in an incident or accident situation and, on the other, the functional capabilities of certain necessary equipment. These inspections almost always include a simulation involving the EDF teams. In 2018, they revealed that the field operators need to be more familiar with the instructions regarding the actions they are required to carry out. ASN also found that these instructions sometimes contain errors, ambiguities, or even instructions that are impossible to carry out, which had not been identified during EDF’s internal inspections. So that EDF can reinforce its ability to control accident situations requiring application of these instructions, ASN more particularly asked EDF to reinforce its technical inspections during the phase validating the documents placed at the disposal of the operators, to ensure the in situ applicability of these documents before they are applied, to improve the clarity and usability of the documents covering the use of mobile equipment in a degraded or emergency situation and to carry out exercises with the use of local instructions. The inspections on the organisation and emergency resources confirmed that the organisation, preparedness and management principles for emergency situations covered by a PUI have been correctly assimilated. Although operating experience feedback from exercises and actual situations is correctly identified by EDF, it does not fully assimilate it, given that certain points requiring improvement are identified time and time again. However, this operating experience feedback shows that the relations between each NPP and the third-parties involved in the management of an emergency situation (hospitals, emergency services) are satisfactory and enhance the interest of such exercises. 286  ASN report on the state of nuclear safety and radiation protection in France in 2018 10 – EDF NUCLEAR POWER PLANTS