Wolfgang Kröger

Critical infrastructures at risk : A need for a new conceptual approach and extended analytical tools

Recent decades have witnessed on the one hand a much greater and tighter integration of goods or services supply systems and growing interconnectedness as well as changing organizational and operational factors, and on the other hand an increased social vulnerability in the face of accidental or intentional disruption. The work of the International Risk Governance Council (IRGC) in the field of critical infrastructures has focused on both the risks associated with five individual infrastructures and the issues associated with the increasing interdependence between them. This paper presents a selection of system weaknesses and a number of policy options that have been identified and highlights issues for further investigation and dialogue with stakeholders. Furthermore, the need to extend current modeling and simulation techniques in order to cope with the increasing system complexity is elaborated. An object-oriented, hybrid modeling approach promising to overcome some of the shortcomings of traditional methods is presented.

The role of network theory and object-oriented modeling within a framework for the vulnerability analysis of critical infrastructures

A framework for the analysis of the vulnerability of critical infrastructures has been proposed by some of the authors. The framework basically consists of two successive stages: (i) a screening analysis for identifying the parts of the critical infrastructure most relevant with respect to its vulnerability and (ii) a detailed modeling of the operational dynamics of the identified parts for gaining insights on the causes and mechanisms responsible for the vulnerability. In this paper, a critical presentation is offered of the results of a set of investigations aimed at evaluating the potentials of (i) using network analysis based on measures of topological interconnection and reliability efficiency, for the screening task; (ii) using object-oriented modeling as the simulation framework to capture the detailed dynamics of the operational scenarios involving the most vulnerable parts of the critical infrastructure as identified by the preceding network analysis. A case study based on the Swiss high-voltage transmission system is considered. The results are cross-compared and evaluated; the needs of further research are defined.

Comprehensive risk assessment for rail transportation of dangerous goods: a validated platform for decision support

Abstract Currently, the most advanced and well documented risk assessments for the transportation of dangerous goods by railway take into account: (i) statistics-based loss of containment frequencies, (ii) specification of potential consequences for a given release situations using event tree methodology as an organisational tool and (iii) consequence calculation models to determine a risk figure known as CCDF (Complementary Cumulative Distribution Function). Such procedures for the risk assessment (including for example decision-making on preventive measures) may offer only a limited insight into the causes and sequences leading to an accident and do not allow for any kind of predictive analysis. The present work introduces an enhanced solution, and a related software platform, which attempts to integrate loss of containment causes and consequences with systems infrastructure and its environment. The solution features: (i) the use of a detailed Master Logical Diagram, including fault/event tree analysis to determine a loss of containment frequency based on different initiating events, scenarios and specific basic data, (ii) the characterization of a resulting source term following a release situation, and (iii) the calculation of various potential impacts on the neighbouring site. Results are wrapped into a CCDF format for each selected traffic segment. The risk-related results are integrated on a software platform, structured as a decision support system using intelligent maps and a variety of GIS (Geographical Information System) data processing procedures. The introduction of the hot spot approach, allows us to focus on the most risk-relevant areas and to use information on various railway infrastructure elements (e.g. points, tunnels), are the basis of the new models employed. The software is applicable to any railway transportation system, comprising its technical infrastructure, rolling stock, human actions, regulation and management procedures. It provides the determination of the annual societal risk due to potential accident scenarios, while also revealing information on the potential causes of an accident taking into account spatial parameters. The approach and software have been validated by a case study done for a particular traffic segment of the Swiss Federal Railway company.

Analyzing maintenance strategies by agent-based simulations: A feasibility study

Abstract Thoroughly planned and implemented maintenance strategies save time and cost. However, the integration of maintenance work into reliability analysis is difficult as common modeling techniques are often not applicable due to state explosion which calls for restrictive model assumptions and oversimplification. From authors’ point of view, agent-based modeling (ABM) of technical and organizational systems is a promising approach to overcome such problems. But since ABM is not well established in reliability analysis its feasibility in this area still has to be demonstrated. For this purpose ABM is compared with Markov chains, namely by analyzing the reliability of a maintained n -unit system with dependent repair events, applying both modeling approaches. Although ABM and Markov chains lead to the same numerical results, the former points out the potentiality of an improved system state handling. This is demonstrated by extending the ABM with operators as additional “agents” featuring their location ( x ; y ) availability (0;1) and different maintenance strategies. This extension highlights the capability of ABM to analyze complex emergent system behavior and allows a systematic refinement and optimization of the maintenance strategies.

Analyzing vulnerabilities between SCADA system and SUC due to interdependencies

Interdependencies within and among Critical Infrastructures (CIs), e.g., between Industrial Control Systems (ICSs), in particular Supervisory Control and Data Acquisition (SCADA) system, and the underlying System Under Control (SUC), have dramatically increased the overall complexity of related systems, causing the emergence of unpredictable behaviors and making them more vulnerable to cascading failures. It is vital to get a clear understanding of these often hidden interdependency issues and tackle them with advanced modeling and simulation techniques. In this paper, vulnerabilities due to interdependencies between these two exemplary systems (SCADA and SUC) are investigated and analyzed comprehensively using a modified five-step methodical framework. Furthermore, suggestions for system performance improvements based on the investigation and analysis results, which could be useful to minimize the negative effects and improve their coping capacities, are also presented in this paper.

Critical infrastructures: the need for international risk governance

Infrastructures (e.g., electric power system, transportation system, information and communication systems) were not designed as integrated systems, as they are operating today. Some infrastructures, e.g., energy, water supply and telecommunications, are so vital and ubiquitous that their incapacity or destruction would affect security and the social welfare of any nation and cascade across borders. They are exposed to multiple threats (terrorist attacks, natural disasters, institutional changes) and their failure might induce risks to other interconnected systems. The paper outlines the urgent need to address such problems with appropriate risk governance and in-time policy analysis at an international level.

Risk assessment of regional systems

Abstract This paper introduces the field of integrated regional risk assessment and safety management for energy and other complex industrial systems. The international initiative includes compilation of methods and guidelines, development of various models and Decision Support Systems (DSS) to assist implementation of various tasks of risk assessment at the regional level. The merit of Geographic Information Systems technology and the use of specialized DSS and stakeholder processes are highlighted.

Advanced Spatial Modelling for Risk Analysis of Transportation Dangerous Goods

The present paper outlines a new proposed risk assessment methodology for transportation of dangerous goods, either by rail or by road, taking into account for the joint calculation of frequencies and consequences, the spatial infrastructure related information embedded into a GIS type database. The methodology is implemented through a user-friendly decision support system (DSS), a specialised type of software platform named CARGO.

Building an Integrated Metric for Quantifying the Resilience of Interdependent Infrastructure Systems

Resilience is a dynamic multi-faceted term and complements other terms commonly used in risk analysis, e.g., reliability, availability, vulnerability, etc. The importance of fully understanding system resilience and identifying ways to enhance it, especially for infrastructure systems our daily life depends on, has been recognized not only by researchers, but also by public. During last decade, researchers have proposed different methods and frameworks to quantify/assess system resilience. However, they are tailored to specific disruptive hazards/events, or fail to properly include all the phases such as mitigation, adaptation and recovery. In this paper, an integrated metric for resilience quantification with capabilities of incorporating different performance measures is proposed, which can be used to quantify the performance of interdependent infrastructure systems in a more comprehensive way. The feasibility and applicability of the proposed metric will be tested using an electric power supply system as the exemplary system with the help of advanced modelling and simulation techniques. Furthermore, the discussion related to the effects of interdependencies among systems on their resilience capabilities is also included in this paper.

Balancing safety and economics

Abstract The safety requirements of NPPs have always aimed at limiting societal risks. This risk approach initially resulted in deterministic design criteria and concepts. In the 1980s the paradigm ‘safety at all costs’ arose and often led to questionable backfitting measures. Conflicts between new requirements, classical design concepts and operational demands were often ignored. The design requirements for advanced reactors ensure enhanced protection against severe accidents. Still, it is questionable whether the ‘no-damage-outside-the-fence’ criteria can be achieved deterministically and at competitive costs. Market deregulation and utility privatisation call for a balance between safety and costs, without jeopardising basic safety concepts. An ideal approach must be risk-based and imply modern PSAs and new methods for cost–benefit and ALARA analyses, embed nuclear risks in a wider risk spectrum, but also make benefits transparent within the context of a broader life experience. Governments should define basic requirements, minimum standards and consistent comparison criteria, and strengthen operator responsibility. Internationally sufficient and binding safety requirements must be established and nuclear technology transfer handled in a responsible way, while existing plants, with their continuous backfitting investments, should receive particular attention.