The US Nuclear Regulatory Commission’s (NRC) review guidance on HSIs, NUREG-0700, defines the HSI as ‘that part of the nuclear power plant through which personnel interact to perform their functions and tasks. Major HSIs include alarms, information displays, controls, and procedures’ (O’Hara et al., 2002). The HSI is used to manipulate a device or system, to request and display stored data, or to actuate a single process or various pre-programmed command routines. HSIs can be organised into workstations consisting of consoles and panels and the arrangement of workstations and supporting equipment could be organised into physical work areas such as a main control room (MCR), remote shutdown station, local control station (LCS), technical support centre (TSC) and emergency operations facility (EOF). The HSI could also be characterised in terms of the environmental conditions in which the HSIs are used, including radiation, temperature, humidity, ventilation, illumination and noise.

The NUREG-0700 definition is generally valid for HSIs currently in use, but it does not take into account the latest advances in HSI hardware and software. (At the time of writing NUREG-0700 was being prepared for a revision.) The following characteristics would generally be associated with ‘advanced HSIs’.