The Spatial Dimension in Human Reliability Analysis

Traditional static human reliability analysis (HRA) methods focus on producing human error probabilities based on qualitative insights derived from operating context such as performance shaping factors (PSF). Especially for field operations outside the control room, travel time between two locations largely determines how long it takes to complete tasks, which in turn affects the success likelihood of the task. While most HRA methods consider required or available time as a PSF, they do not adequately account for spatial dimensions that influence time. This paper outlines the importance of the spatial dimension for HRA. Location affects the availability of tools, the workload of the operator, and the complexity of the task. The need to travel from one location to another can considerably change the context of the task and even has implications for error dependency. This paper outlines considerations for location and movement and presents use cases to explore how spatial HRA could be treated for balance-of-plant and main control room tasks. The spatial dimension complements recent developments in dynamic HRA. Dynamic HRA, which uses simulation techniques to model human performance, implies primarily a temporal dimension. Dynamic HRA captures the evolution of an event over time; however, dynamic HRA is incomplete without consideration of location. Spatial HRA is part of a broader approach joined with dynamic HRA that is called computation-based HRA (CoBHRA).

Keywords: Human reliability analysis, Computational risk assessment, Dynamic, Spatial, Location, Movement.

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