PSI - Issue 28

Dmitry O. Reznikov et al. / Procedia Structural Integrity 28 (2020) 1360–1368 D.Reznikov, N.Makhutov,O.Yudina / Structural Integrity Procedia 00 (2019) 000–000

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the HIF, the presence of dangerous defects and local failures of individual HIF components capable of initiating accident scenarios). The implementation of these developments allows one to create a scientific and informational basis for making sound management decisions related to the functioning of HIF, in particular, to make decisions on the possibility of further operation of the facility, on the implementation of protective measures, repair programs, or, in other words, on carrying out risk based management of the hazardous industrial facility. Hazardous industrial facilities are complex technical systems, characterized by the non-linearity and non determinism of the processes occurring in them, the probabilistic nature of the dependencies between the parameters of their state, the presence of bifurcation modes and, therefore, the multiplicity of development scenarios, some of which are catastrophic. In this regard, the operation of these facilities becomes impossible without risk assessment, development of regulatory criteria for accepting risks and procedures aimed at reduction of risk to those levels which the company is ready to put up with for the sake of the benefits provided by these systems. Awareness of the impossibility of implementing the concept of absolute safety (zero risk) led to a transition to the concept of acceptable risk, the essence of which is that the risk cannot be completely eliminated, but can be reduced to an acceptable level which the state and society are ready to put up with at current stage of economic development. Currently, this concept forms the basis of almost all risk management programs. When using it, one of the key issues is the question of risk regulation, which is understood as the process of setting the level of unacceptable of risks [ R ], which cannot be exceeded under any circumstances, and the level of broadly acceptable (or negligible) of risks { R } that at the current stage of economic development the regulatory authorities consider as negligible. Risk regulation is a key element of the risk management process and the process of making decisions regarding the implementation of protective measures and the possibility of further operation of the facility. Moreover, the regulation can be based on: - probability of accident (for example, the limit probability of death in an accident can be established); - consequences (for example, losses exceeding a certain value may be considered as unacceptable); - combined indicators (for example, by the product of probability and consequences). The selection of the limit value of tolerable risk depends on many factors, in particular: on the availability of risk reduction technologies, the nature of requirements and restrictions on the part of supervisory authorities, the perception of risk in the society at large and by the specific decision-makers. The normative limit value of tolerable risk should be, on the one hand, low enough so as not to cause concern of the people who are exposed to it, and to ensure acceptable safety of society. On the other hand, it should be technically feasible and not impede economic development due to the excessively high costs that are needed to reduce risk to the selected acceptable level. A compromise between these two conflicting requirements depends on the level of technological, social and economic development of society and is achieved in the process of coordinating the interests of various parties involved. 2. Risk regulation The issue of risk regulation can be considered on the example of individual risks. When assessing individual risk, the possibility of human death is taken into account under all possible scenarios of accidents at the considered HIF, and only two states of a person are distinguished: “alive” (consequences are 0), “dead” (consequences are 1). In this formulation, the magnitude of the consequences will not be included in the expression for this risk index. Thus, the individual risk is defined as the probability of death of one pre-selected person (for example, an operator, a staff representative or a person living in a neighboring territory) over one year period, due to potential accidents at the facility under consideration (Makhutov, et al. 2006). The estimation of the individual risk induced by the hazardous industrial facility is based on the assessment of its scenario tree according to equation (1). It is a common practice to distinguish the average individual risk for the personnel of the HIF (or the population of adjacent territories) and the maximum individual risk for a person (operator), who is the most exposed to dangerous factors of the HIF.