The challenge in nuclear power plant modernization projects is ensuring safe and functional connectivity between existing and new systems. Safety and functionality need to be proven in advance so that the wanted changes are licensed and approved by the operator and the regulator. With the help of dynamic simulation the technical concept can be tested in all design phases and plant operators can be involved early on in the project in functional testing and design work. Dynamic simulation is one part of ensuring smooth commissioning during tightly scheduled nuclear power plant (NPP) outage.

In Fortum's Loviisa NPP the original emergency diesel automation systems are modernized. The role of emergency diesels is to automatically provide power for safety critical components during a total loss of off-site power. The emergency diesel automation consists of safety classified I&C cabinets (analog) and non-safety classified I&C cabinets (PLC) and Human-machine Interphase (HMI) systems (physical controls and touchscreen). The automation functions include different operation and control modes, testing functions and protection functions. Functionalities are too complex to evaluate with pen and paper, especially during fault situations and simultaneous activity of safety classified and non-safety logics. Tight schedule of the NPP overhaul limits the available time for on-site testing.