Synchronous vs. Asynchronous Coupling in the HUNTER Dynamic Human Reliability Analysis Framework
Authors: Ronald Boring, Thomas Ulrich, Roger Lew, Jooyoung Park
Abstract: The Human Unimodel for Nuclear Technology to Enhance Reliability (HUNTER) framework for dynamic human reliability analysis (HRA) has recently been developed into standalone software. HUNTER creates a virtual operator that is coupled to a virtual system model, in this case a nuclear power plant model. Asynchronous model coupling is most often found in the use of thermohydraulic codes like RELAP5-3D, which are designed to run in batch mode without interruption to determine the evolution of plant parameters from a particular set of conditions. Within RELAP5-3D, it is possible to schedule changes in the configuration, but conditions are determined a priori and not changed once a particular simulation run is started. In contrast, synchronous model coupling is most commonly found in interactive simulators, which feature a system model linked to real-time inputs from a human user. A model that is executed is a simulation, while a simulator is a simulation designed to interact with human inputs. Simulation is typically asynchronous to other models or humans, whereas simulators are synchronous with regular exchanges to other models or humans. For example, a training simulator at a nuclear power plant operates synchronously in such a manner that an input from the reactor operator at any point in time will change the evolution of the simulation run. The simulator provides an evolving response to dynamic contexts that reflect operator actions. The ability to change the simulation direction mid-course is the hallmark of synchronous coupling. HUNTER, as virtual operator, most accurately reflects human-system interactions when it is coupled synchronously with a plant model. In this paper, we explore synchronous and asynchronous coupling based on implementations in HUNTER.
Keywords: human reliability analysis, HUNTER, dynamic, coupling, simulator
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