Methodology and Principle for Emergency Operation Computerization in Loviisa NPP Automation Renewal Project

Loviisa NPP has two VVER 440-type pressurised-water reactors. The automation renewal project started in the beginning of 2005 when Fortum signed a contract with a consortium of AREVA-NP and Siemens AG. The functional concept of the new I&C is defined in terms of task categories. In normal operational conditions the nuclear power unit is controlled by normal process control functions. Also safety-related preventive protection functions may be activated. Reactor protection functions are activated in operational transients and in accidents. Also diverse manual and automatic backup of the Reactor Protection System is foreseen. After an operational transient or an accident the operators steer the plant to a safe state using plant shutdown or accident management functions. The new control systems and Man Machine Interface (MMI) will be implemented using safety and non-safety digital control platforms and user interfaces. In addition to these conventional non-digital platform with dedicated MMI will be provided to control selected critical functions. Loviisa NPP is using Emergency Operating Procedures (EOP) designed together with AREVA-NP, EdF and Fortum consisting of event and state oriented procedures. This set of procedures is being adapted to a functional concept of the new I&C together with AREVA-NP and Fortum. The rules for organisation of operation with different EOPs and MMIs and the principles and methods of computerization of the EOPs are defined. The rules for organisation of operation with different EOPs and MMIs are designed taking into account requirements set for different task categories and criticality of the actions to be performed by the operator. Priority to the safety MMI is given in case of critical actions. Conventional MMI is used if fast operator response is required. The principles and methods of computerization of the EOPs are consistent with the concept developed for the French EPR and also for the new Chinese plant. This concept takes into account the N4 plant feedback. One of the main targets of the EOP computerizations is to keep the design of operation and support screens close to the present ones.