Sammendrag
Identification and assessment of hazards and risks in the activities of the process industry are of paramount importance for the prevention of major accidents. Although several techniques of HAZard Identification (HAZID) and quantified risk analysis have often been proved effective in the industry, they generally lack the dynamic dimension of risk management. In other words, they lack the ability to learn from new risk notions, experience and early warnings. When carrying out HAZID and risk assessment, there is the need to know how to deal with atypical accident scenarios as soon as their emergence is demonstrated. The related risk needs to be addressed in an ever-changing environment. In fact, what is not identified or assessed cannot be prevented or mitigated and latent risk is more dangerous than recognized one due to the relative lack of preparedness. This study proposes a dynamic approach to risk by coupling an advanced technique for hazard identification to an innovative method for risk assessment: the Dynamic procedure for atypical scenarios identification (DyPASI) and the Dynamic risk assessment (DRA) method. DyPASI was developed within the EC project iNTeg-Risk. This technique aims to complete and update HAZID. Atypical accident scenarios, which by definition are deviating from normal expectations of unwanted events or worst case reference scenarios, are identified through a systematic screening of related emerging risk notions. The DRA method aims to estimate the updated expected frequency of accident scenarios by means of Bayesian inference. Real time abnormal situations or incident data are used as new information to update the failure probabilities of the system safety barriers, which necessarily affect the overall scenario frequencies and the related risk profile. The BP Texas City refinery accident, that occurred on 23 March 2005, was considered as a case study. The results obtained from the application of the dynamic risk approach show that the accident should have been expected and its occurrence probability could have been reduced through this approach. The results highlight the need of safety culture and decision-making processes capable of dealing dynamically with emerging and increasing risk issues.