Proceedings of ICAPP 2007 Nice, France, May 13-18, 2007 Paper 7001 Some Aspects of Integrating Risk and Security Aspects for Complex Systems Analyses Christian Kirchsteiger, Dan Serbanescu European Commission, DG JRC, Institute of Energy, Westerduinweg 3 - 1755 LE Petten, The Netherlands, Tel +31.224.56.5395, Fax: +31.224.56.5641, Email:Christian.kirchsteiger@jrc.nl, dan.serbanescu@jrc.nl Abstract – The development of risk analyses is tightly connected with the efforts to model various complex systems. For the nuclear field, the process of refining risk analyses, which evolved in Probabilistic Risk Analyses (PRA) well standardized and documented methods this effort to integrate new risk calculations challenges to the general aspects of modelling complex systems is very important. The evaluation in integrated analyses of both safety and security challenges to complex systems and in particular to Nuclear power Plants (NPP) is one of the issues included in this generic trend. The aspects of plant security were in general treated in so called deterministic type of approaches and there were limited attempts to try to use risk analyses approaches for such aspects. On the other side recent events showed the importance of improving the tools of security evaluations and integrating them in the evaluation of the NPP as a whole from any kind of risk. However integration of PRA techniques for the evaluation of security challenges into the safety models of risks has some basic dilemas These questions are mainly related to the acceptability of such a common safety-security probabilistic modelling, or in other words how feasible is to use PRA methods for such a common modelling and which are possible solutions to the difficulties of the implementation of general PRA like techniques. From this perspective this is quite an old topic in PRA, for which the answers were mainly pessimistic so far. The paper presents some aspects to be considered for a potential new evaluation of the status of this safety-security models merging process. The proposed directions for future research are illustrated with results obtained for hypothetic case models If successful such a global modelling has the benefit of being a better support to the decision making process, as well as for complex systems design optimizations on various objectives (safety, security etc.). I. INTRODUCTION In order to evaluate the risks, to which a Complex System (CS) is exposed due to safety and security challenges it is necessary to develop models and adequate to them methods of risk analysis. However in the nuclear field, the risk analyses, which evolved in Probabilistic Risk Analyses (PRA) are well standardized and documented and models and tools already exist. That is why it is worthwhile to evaluate the possibility to integrate new risk calculations challenges to the general aspects of safety in unitary approaches. On the other hand the evaluation in integrated analyses of both safety and security challenges to complex systems and in particular to Nuclear Power Plants (NPP) is one of the new issues included in this generic trend to check if existing approaches could be expanded to new challenges and to evaluate the needed changes to them to be properly used for these new tasks. The aspects of plant security were in general treated in the so called deterministic type of approaches and there were limited attempts to try to use risk analyses approaches for such aspects. Integration in the PRA techniques of the models and methods for the evaluation of security challenges into the safety ones has known difficulties in the PRA world. These problems are mainly related to the questionable acceptability of such a common safety-security probabilistic modelling, or in other words how feasible is to use PRA methods for random challenges and deliberate challenges all along in one model.