Applying Markov Processes for KIC Minimum Configuration Calculation

CPR1000 plant operation is based on a centralized and computerized control mean (the KIC system), that provides all the means needed by the shift team to operate the plant in any situation. There are two main consequences regarding the definition of the KIC configuration. 1) The KIC composition shall be defined so that they are sufficient for the shift team to finish their tasks. It is linked to “Human Factors” concerns as well as organization concerns. 2) The probability of KIC OWP (Operator Work Place) unavailable shall be taken into account in order to figure out the relationship between the fault leading to KIC OWP unavailable and different KIC degraded situation. The technology and architecture choices fix limits to the flexibility and robustness that the KIC can offer regarding its own degraded situations. Therefore, in order to keep a low frequency of use of the Back-Up Panel, it might be needed to adapt and review the operating organization and needs to stay on the KIC by raising the discomfort of operation for the shift team. Nevertheless, such an approach is limited as reducing the discomfort of operation as obviously a price in term of safety notably. Therefore, the KIC degraded situation shall be studied in order to identify the criteria beyond which the safety operation of the plant cannot be ensured anymore from the KIC. After studying the features of the fault leading to KIC OWP key component unavailable, the data from DCS supplier, the data from reference NPP (Nuclear Power Plant) and the statistic during commissioning, the MTBF (Mean Time Between Failures) for each OWP has been calculated. Applying Markov Processes based on the studying above, CPR1000 operation principles, features of SOP (state oriented procedures to deal with accident situation) and PSA, CNPEC suggest the method to calculate KIC minimum configuration for reaching the best balance to maximize the availability of the KIC, to minimize frequency of switch to the Back-Up Panel (conventional control means) and to increase the plant availability (as the switch to the Back-Up Panel can lead to the fallback of the unit).