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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Fig.2. Levels of individual risk I is the region of unacceptable risks in which risk cannot be justified except in extraordinary circumstances. II is the region of tolerable risks where people and society are prepared to accept risk in order to secure benefits according with the ALARP principle III is the region of broadly acceptable risks where risks are regarded as negligible (or insignificant) and do not require special risk reduction measures Usually two criteria values of individual risks are established: the limit value of tolerable individual risks [ R i ] and the limit value of broadly acceptable (negligible) individual risks { R i } (Fig. 2). The establishment of a specific numerical value of the tolerable individual risk [ R i ] is a fundamental, socially significant issue. Obviously, the determination of this value falls within the competence of the country's political leadership and is based on the desire to establish a specific numerical value for the value of [ R i ] at such a low level as is technically achievable. However, it must be borne in mind that such a desire is associated with very high economic costs of the required risk reduction measures which could lead to the unprofitability of the economic activity itself. Thus, when establishing the specific value of the tolerable individual risk a priority should be given to the social aspects of the problem. But the level of economic development of the country should also be taken into account. The adopted specific value of [ R i ] must comply with social requirements and at the same time cannot become a prohibitive barrier (i.e. impose excessive restrictions) for the implementation of economic activity, ensuring efficiency and further development of the country's economy. The increase of the level of economic and technological development allows the regulatory authorities to establish lower levels for the criteria values of individual risk. In (Health and Safety Executive, 2001) the following formula was proposed to assess the limit value of tolerable individual risk: where β is the so called policy factor that depends on the degree of voluntariness with which a person is engaged in this activity and the degree of his interest in the results of this activity. The value of β varies in a wide range: - β ~0.01-0.1 if a person does not make voluntary decisions about being at risk, and does not receive any benefits from the activity that generates this risk; - β ~10-100 if a person consciously and voluntarily engages in hazardous activities, hoping to receive significant benefits: The criteria value of broadly acceptable risk is defined as: 4 [ ] i R 10     (4)