Method for Enhancing Evaluation of the Human Error Probability in Disaster Risk Assessment for Industrial Plants
Authors: Mamiko Murahashi, Yusaku Okada
Abstract: An important part of considering countermeasures for disasters in industrial plants is to conduct an accurate risk assessment. In general, we assess risk based on two indicators: the harm severity and the probability. We first select candidate countermeasures based on the harm severity. Next, the specifications of countermeasures such as the scope of application, expected lifetime and cost are determined, taking into account of the probability. As a result, we introduce appropriate countermeasures in the field that can control risks within acceptable limits.Various countermeasures for disasters caused by human error are considered similarly and introduced in the field. It is necessary to analyze the factors related to human error, which are called performance shaping factors, in order to evaluate the human error probability. For this purpose, workers with appropriate knowledge and ability of human factors must be assigned to the risk assessment team. However, it is difficult for many industrial plants to secure the required number of workers who can accurately analyze and evaluate the effects of human factors. At the accident level, it is possible to invite human factor experts to the analysis team because the budget for the analysis is large. On the other hand, the budget for an incident analysis is limited because of the large number of incidents. The purpose of this study is to support the enhancement of incident-level disaster risk assessment. We examine the assessment method of the human error probability that can be conducted by those with limited knowledge of human factors.We attempted to evaluate on a scale of six (5: Certain, 4: Likely, 3: Possible, 2: Unlikely, 1: Rare, and 0: Eliminated), which are commonly used in risk assessments, rather than to calculate detailed values such as the human error probability.First, we organized and classified factors related to the occurrence of human error by text mining of disaster incident cases over the past 20 years. Second, we referred to a number of past studies on performance shaping factors and constructed [the database of factors influencing on human error risk]. Finally, we developed a system to evaluate the human error probability by extracting keywords and sentences from incident reports of industrial plants and matching them with [the database of factors influencing on human error risk]. The system consists of the following functions.(1)Extract keywords w_i and sentence data S_j=(w_1,w_2,…,w_k) that keywords are concatenated from an incident report.(2)Check S_j against [the database of factors influencing on human error risk] to estimate the influence on the human error probability. The estimated impact for S_j is x_i.(3)Comprehensively evaluated x_i. This overall impact evaluation value is denoted as Y.(4)Indicate the human error probability by a 6-level value based on Y.(5)Adapt the estimated human error probability and the harm severity entered separately to a commonly used risk matrix.We proposed a method that can be adapted to the risk matrix used in general disaster risk assessment. This method was validated by several safety administrator in an industrial plant and its validity and feasibility were confirmed. However, it is a problem for practical application to link with the incident report design because it is sometimes difficult to adapt to this method depending on the incident report design.
Keywords: Human Reliability, Risk Assessment, Accident Report Analysis
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