A Taxonomy of Human Tasks for Human Reliability Analysis of Small Modular Reactors

Small Modular Reactors (SMRs) represent a radical shift in how nuclear power plants (NPPs) will be operated.SMR designs propose advanced characteristics such as smaller, simpler plants, increased use of automation, and increased reliance on inherent safety properties and passive safety systems.This allows for new operating paradigms such as remote, autonomous and/or multi-unit operation, reduced staffing plans, and alternative applications such as hydrogen production, and district heating.As a result, the role of the human in the operation of SMRs is anticipated to change by comparison to conventional large NPPs.For Human Reliability Analysis (HRA), this means that that our current knowledge and assumptions about human performance may no longer be valid, as these are based on analysis of operator actions at conventional plants.Further, existing HRA approaches may not adequately capture the extent, or impact, of the potential changes to operational tasks and scenarios.At the same time, the role of the operator as a safety barrier in an SMR is expected to be at least as important as at a conventional NPP as it is highly likely that human operators will still form part of the defence-in-depth strategy if automated, inherent, or passive safety systems fail or do not work as required.The Swedish Radiation Authority has recently awarded funding to Risk Pilot AB for a project to investigate the types of tasks that operators will be expected to perform in an SMR plant, with emphasis on the identification of new types of tasks that differ from conventional NPPs.In this paper we will present some key findings from a literature review and how these inform our initial attempts at the development of a task taxonomy to support HRA for SMRs.