J. Hugo

Idaho National Laboratory, Idaho Falls, ID, USA

7.1 Introduction

Current and emerging nuclear power plant (NPP) design strategies include ambitious goals of reliability and safety. It is expected that these goals would be met partly by judicious implementation of new materials, new technologies and new concepts of operations. The general consensus is that current levels of safety could only be enhanced by smaller reactor units designed for a high level of passive or inherent safety in the event of malfunctions and that efficiency could only be improved by extending the energy output of the reactors to more diverse customers. To meet these challenges, several emerging designs for small modular reactors (SMRs) make provision for non-electrical applications in their concepts of operations. These new concepts require advanced technologies like instrumentation and control systems to support thermal-hydraulic processes associated with different fuels, different reactor coolants and different product streams (steam, process heat and electricity in various combinations). New technologies are also required to support new concepts of operations like modular plant operation, high levels of automation and reduced staffing.

Other chapters in the Handbook discuss the functional and physical characteristics of SMRs as well as their economic considerations, but the following two paragraphs will briefly put those considerations into context for human-system interfaces (HSIs) and human factors.

The term ‘modular’ refers to the ability to fabricate major components of these new plants in a factory and shipping them to the construction site. Although current large NPPs incorporate factory-fabricated components (or modules) in their designs, a substantial amount of fieldwork is still required to assemble components into an operational power plant. In contrast, SMRs are envisioned to require limited on­site preparation and to substantially reduce the lengthy construction times that are typical of the larger units. SMRs would provide simplicity of design, enhanced safety features, the economics and quality afforded by factory production, and more flexibility in terms of financing, siting, sizing and end-use applications, compared to larger NPPs. ‘Modular’ also refers to the incremental or phased approach to establishing total plant electrical output. This means that additional modules can be added and commissioned incrementally as the demand for energy increases and thus allowing for an early return on investment.

Economy of scale (that is, total cost defrayed against a larger electrical output)

Handbook of Small Modular Nuclear Reactors. http://dx. doi. Org/10.1533/9780857098535.2.149

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is a key advantage for the operation of large reactors, but their capital cost and operations and maintenance costs (O&M) are very high. Although SMRs lose the benefit of economy of scale due to the lower electrical output per reactor, they compensate instead with lower capital cost due to smaller components and the use of standardized, relatively mass-produced components and systems. O&M cost for SMRs includes the normal production management activities such as scheduling, procedures, and work control and optimisation. It also includes the maintenance activities such as routine, preventive, predictive, scheduled and unscheduled actions aimed at preventing equipment failure or decline with the goal of increasing efficiency, reliability and safety. In order to be competitive, SMRs therefore need to compensate by achieving operations economy through innovative concepts of operations, which includes higher levels of automation, reduced staffing, on-line refuelling of separate modules, remote monitoring of operations and advanced HSI technologies to support error-resistant operations.

HSI technologies will play an important role as part of resilient control systems that aim to limit the occurrence and effect of human error, while also contributing to overall plant performance. However, these advantages will not be achieved without far more rigorous attention to the roles and functions of both humans and systems. Because of this, designers of the new generation of power plants need to include human factor considerations in the overall engineering process right from the start of the project, and specifically in the selection and deployment of HSI devices. In many older NPPs human factor considerations were often an after-thought in design (Three Mile Island being a classic example). Designers of new power plants, however, have an opportunity to eliminate many of the errors of the past by integrating human factors right from the start and by following the excellent guidance currently available from the sources listed in the Reference section of this chapter.

Unlike a past generation of analogue control and display devices, modern HSIs are not designed exclusively for the nuclear industry. Many of the new devices are consumer appliances that are functionally suitable for deployment in the control room or outside in the plant. However, there may be several instances where the nuclear plant’s technical and environmental conditions would impose requirements that are not generally met by standard consumer devices. For example, there would be requirements for ruggedisation of handheld devices, seismic and vibration protection of mounted devices, protection from electromagnetic interference, protection against cyber-attacks, and many more. Also, consideration of the roles of humans and machines requires more critical analysis of how the implementation of new technology would affect the way functions are allocated between humans and systems than ever before.

Although new HSI technologies have the potential significantly to improve operator performance in the field and in the control room, the nuclear industry lacks well-defined criteria to ensure that new displays and controls would support human performance and also ensure operational effectiveness and safety. Without such criteria to guide the selection and deployment of new HSI technologies, designers may unwittingly create opportunities for error.

The simple rule that instrumentation and control engineers will have to learn in

NPP design is that functions should not be automated just because technology makes it possible. Instead, human-factor principles would dictate that automation decisions should be based upon a rational trade-off between the contribution that either system or human, or a combination of the two, would make to operational effectiveness and safety.

To understand these trade-offs, system engineers and human factors engineers should understand the context and conditions where new technologies would be applied most effectively. This includes interdependent aspects such as human performance requirements as well as process and system characteristics like reliability, quality and usability. In combination, these aspects would help to determine the most appropriate selection of HSI technologies.

In anticipation of requirements that may be unique to advanced reactor designs like SMRs, designers are now facing a number of tough requirements. For example, they must identify the advantages and disadvantages of technologies and accommodate them in the power plant design. This must include the context of use (for example, the operational domain, such as control room, field operations, maintenance or materials handling, and the operational condition that determines the nature of the operator’s task). It also requires consideration of specific human-factor constraints (perceptual limitations, workload, human reliability, situation awareness and performance-shaping factors), safety requirements, and the projected lifetime of products.

One of the requirements that demands considerable insight into the nature of HSI and operational requirements is to determine the optimal interaction modalities for different operational contexts. This needs to take into account spatial and physical work space characteristics and collaborative functions such as crew-system coordination, contextual adaptation, and means of communication to support shared situation awareness. Designers would also have to consider alternative perceptual and interaction modalities offered by new technologies like touch and voice interaction to simplify information access, communication and decision-making and to reduce errors. Ultimately they have to determine how new technology characteristics affect human performance and therefore the need for advanced capabilities to support new power plant requirements, such as reducing operational and maintenance costs by reducing the number of operators needed to manage control room tasks. This requirement leads to questions about the need for adaptive automation, computational intelligence, operator support systems and other methods of reducing complexity, to optimise human-automation interaction. Where appropriate nuclear operating experience of advanced technologies is lacking, designers may have to resort to obtaining research information to resolve these issues.

In spite of all the requirements that will be imposed on designers to verify and validate their choice of technologies, there is already ample evidence in other industries of the benefits of the advanced technologies described in this chapter. These HSIs offer support for substantial improvement in the safety and economics of all nuclear power plants. The SMRs that are the subject of this Handbook promise to be safer and more economical plants that will reach the market in the next decade in various countries. That is just one reason why the adoption of the HSI described here is a logical approach in current SMRs and other advanced designs. Nevertheless, designers cannot simply assume that any new technology would contribute to safety or better human performance. Addressing issues of automation, function allocation, error reduction and overall operator efficiency is still a major challenge. To address those challenges three main topics are discussed in this chapter:

• The technical characteristics of HSIs for a new generation of NPPs and the human factors considerations associated with them.

• Implementation and design strategies: special considerations for the selection and deployment of advanced technologies in NPPs, whether modernised, new, conventional or first-of-a-kind (FOAK), including strategies for the integration of human factors and regulatory aspects into systems engineering processes.

• Future trends: how technologies are likely to develop over the next 10-15 years and how this will affect design choices for the nuclear industry.