The currently proposed SMRs (IAEA, 2014) have new design features and technologies that may require new tools and measures for safeguards and security. Some safeguards and security considerations for SMRs may be different from those for a large reactor.

For example, there may be issues associated with the fuels such that the existing accountancy tools and measures may need to be modified or further developed for reactors using non-conventional fuel types. Further, issues may arise about new fuel loading schemes, as reactor cores with extremely long lifetimes may require innovative surveillance tools and measures, and long-life sealed core replacement may present novel accountancy challenges.

International safeguards typically verify the operator’s declaration of activities with nuclear material. These declarations address the receipts, shipments, storage, movement, and production of nuclear material. Inspections depend on the material

type and whether the material is irradiated. The IAEA state level approach (IAEA, 2010) will in addition take into account the technical capabilities of the state including the possible existence of other nuclear activities (including commercial or academic R&D) and the location of the facilities.

Safeguards considerations will take into consideration differences in various factors; i. e., the accessibility to the nuclear material, whether the reactor facility is operated continuously, how the reactor facility is refueled, the location and mobility of the reactor facility, and the existence and locations of other nuclear facilities in a given state.

For example, for nuclear materials that are normally not available to the host state, if the vendor state delivers a sealed unit that operates until the vendor replaces it with a new one, at some later time, and there is no storage capability for used fuel in the host state nor equipment to handle used fuel — this could raise issues, such as whether the reactor can not only be ‘sealed’ by IAEA and treated as an item, but whether remote monitoring of the seal can readily detect any attempt to open the reactor. When comparing equivalent generating capacity, i. e., many SMRs with the same total capacity with one large LWR, inspection issues would deal with whether SMRs will be co-located or separated at different sites. Additional issues would deal with their refueling schemes and whether they would be different, and whether there would there be separate used-fuel storage for each module.

In the case of many small reactors in remote (e. g. arctic) separated locations compared to one large centrally located reactor with a large electric grid, it would be necessary to consider inspector ease of access to the remote site as well as the possibility of building an electrical distribution grid. Other considerations are: load — dependent vs. base-load reactors; stand-alone sole source of energy supply; offshore SMRs on floating barges tied to a state/regional grid; control vs. ownership.

The following considerations could apply to any new installation, including SMRs:

• Fuel leasing or supply arrangements that avoid on-site storage of fresh and/or used fuel.

• The isolation of the site or mobility of the reactor (sea or rail) might be a factor. Consideration should be given to access issues for both inspectorate and the adversary.

• Remote monitoring: There should be discussions between the operator/State/IAEA about small reactors which evaluate the potential of remote monitoring, including transmission of data off site.

• Will there be a different approach to physical protection and how might that affect the safeguards tools?

• Will the site or nearby sites have more or less ancillary equipment like hot cells, pin replacement capability, fuel storage, or nuclear research activities?

• Will the containment features be shared by multiple units; will there be underground containment?

The following discussion pertaining to physical security is derived in part from ideas in a white paper by the Nuclear Energy Institute (NEI, 2012), but with some change in emphasis.

Some of the same features that are being included in the design of SMRs as safety improvements may also improve their protection against physical threats. One feature common to some SMR designs is a compact reactor coolant boundary, contained mainly within the reactor pressure vessel (RPV). This feature may enhance the safety of light-water reactor-type SMRs, because large-break loss-of-coolant accidents (LOCAs) may not need to be considered for these reactor types. This could also be potentially advantageous against deliberate acts.

Some SMRs may have a number of passive physical barriers and simplicity in systems required for safe shutdown. These may include such features as RPVs and containment vessels located underwater or below grade, the reactor building located partially or completely below grade, and fewer safe shutdown systems and components requiring physical protection. The below-grade installation of some SMRs may provide additional security benefits, such as minimizing aircraft impact, limiting access to vital areas and the communication ability of adversaries. These features may provide a means of enhancing security system effectiveness against radiological sabotage. Use of the traditional multilayered defensive approach of deterrence, detection, assessment, delay, and interdiction can potentially be used effectively for physical protection of SMRs. Deterrence, detection, and delay concepts could be addressed in the early design phase of a facility in order to provide sufficient response time for on-site security force response. The ability to rely on an effective onsite response to a security threat is a potentially important factor that should be considered at the initial conceptual design phase to ensure sufficient intruder delays are included.

Examples of methods for extending adversary delay times, which in principle also apply to large plants that can be incorporated into SMR designs include:

• locating and configuring vital components so that gaining access to these components is extremely difficult and time consuming for an intruder;

• locating and configuring critical safety systems so that there is no capability to destroy a target set from a single location;

• incorporating multiple layers of delay barriers against intruders and minimizing the number of access points to areas containing vital assets.

To the extent that SMRs are in the early stages of design or conceptual development, the above bullet items could be considered without the need to do potentially costly retrofits if these are considered after a plant is built.

One should also consider physical security system design options which minimize human involvement in security events (i. e., lower security risk profile), minimize impact of necessary future system modifications, and maximize adversary delay times. Examples include:

• designing the facility with minimum access points and multiple passive barriers based on a defense-in-depth approach to physical security;

• using redundant detection, assessment and delay systems;

• using modular capabilities in physical security systems to minimize impact on station security staffing for system maintenance as well as upgrades needed to address system technology obsolescence and potential future increased design basis threats.

Again, to the extent that SMRs are in the early stages of design or conceptual

development, the above bullet items could be considered without the need for potentially costly retrofits if these are considered after a plant is built.

A regulatory issue of importance related to physical security of SMRs is security staffing. Security staffing directly impacts operations and maintenance (O&M) costs and as such constitutes a significant financial burden over the life of the facility. SMRs are significantly smaller in size and system complexity which translates to improving security efficiency.

Key features of the physical protection programs that affect staffing expectations for nuclear facilities include:

• defense in depth using graded physical protection areas: increasing protection and control as vital equipment is neared (with well-defined boundaries);

• access authorization programs;

• robustness of intrusion barriers;

• alarm assessment to distinguish between false or nuisance alarms and actual intrusions and to initiate response;

• likely response to intrusions.

As discussed above, some general considerations for PR&PP assessments of SMRs are as follows.

• Smaller power reactors have smaller radiological inventories and thus potentially smaller releases during off-normal conditions.

• Smaller reactors have a smaller physical footprint, which can potentially lead to a smaller security force and fewer needs for surveillance and otherwise reduces the target area size.

• Some designs have potentially longer fuel cycles, which can potentially lead to fuel being inaccessible for longer periods of time.

• Smaller designs have potentially constrained ingress and egress, which makes detection and monitoring simpler.

• Ease of fuel assembly transport for some designs, which needs to be recognized and assessed.

• Higher enrichment levels for some SMRs relative to conventional light-water reactors, which need to be recognized and assessed.

• Remote locations of facilities present new challenges for inspections.

• Transportable facilities present unique technical and institutional issues relative to stationary facilities.

• Potential for a reduced security force.

• Potential for a reduced emergency planning scope.

The discussion given above applies generally to many SMRs currently under consideration. For the integral pressurized water reactors (iPWRs), which is the focus of this section of the Handbook, there are some distinguishing characteristics that may be pertinent for non-proliferation and security. Since the iPWRs are based on the larger, more familiar PWRs, it can be anticipated that international safeguards for the iPWRs could be developed from the basis of the current safeguards for large PWRs. Less conventional SMRs, of more novel designs, may require the development of additional specialized safeguards approaches. For iPWRs that have fuel enrichments similar to large PWRs, the material attractiveness considerations should be similar.

If the iPWRs operate with closed reactor vessels in a manner similar to large PWRs and have comparable fueling periods, this then offers a comparable barrier to fuel accessibility. If the iPWR can maintain a small physical footprint relative to other SMR designs then this could be a security advantage.

10.6.1 Deterministic scenarios

The economic analysis and comparison between SMRs and LRs, has given great emphasis to the capital costs that dominate nuclear generation costs, as a very capital­intensive technology. The cost comparison between LRs and multiple SMRs has been

110

105

100 95

Figure 10.14 Design saving factor ranges of different SMR fleets deployed in large sites (4500 MWe), compared to a very large reactor unit (Boarin and Ricotti, 2011b).

assessed based on very conservative assumptions that almost disregard savings by design at SMRs. Under this assumption and considering ideal or expected construction costs and schedule for LRs (i. e. no delays and no cost overruns), scenario analysis of alternative LR and multiple SMR projects confirms a comparable or higher economic performance of LRs, essentially due to the economy of scale on construction costs. On average, investment IRR and profitability index (PI) of LRs are 1-1.5% higher than SMRs (Boarin and Ricotti, 2009). This slight difference, applied on a relevant project investment value, translates into a significant project value increase. This holds in deterministic scenario conditions, with conservative assumptions on SMRs and ideal assumption for LRs, with no uncertainties affecting the scenario evolution (Boarin and Ricotti, 2011a).

Nonetheless, multiple SMRs have economic features that make them competitive with large NPPs under different perspectives than mere profitability. Multiple SMRs offer financial benefits that encompass intrinsic investment modularity. Investment modularity and scalability are intrinsic features of multiple SMRs that allow adaptation of the investment program to the electricity and financial market evolution. Current projected schedules of SMRs are in the range of four years for the first-of-a-kind (FOAK) and down to two years for a n-th-of-a-kind (NOAK), in some designs. This shorter construction time is due mainly to smaller size, simpler design, increased modularization, higher degree of factory fabrication and series fabrication of components.

The shorter construction schedule and the smaller output size make SMRs more readily adaptable to market conditions, both temporally and spatially. The shorter lead times and the plant capacity allow to split the investment in a closer proximity to the market evolution: if not needed, the construction of an additional SMR unit can be avoided whereas a monolithic LR investment may result in an unexpected overcapacity installed. Whereas market conditions are highly uncertain, the SMR modularity translates in adaptability; the investment flexibility in the plant deployment has an associated economic value, which is caught by real option analysis. It is demonstrated that this economic value is positive and accounts for the possibility of avoiding financial losses in market downturn and reaping early revenues in favourable market conditions. The chance to better cope with the probability of a change in the economic environment reduces the gap of competitiveness between LRs and SMRs (Locatelli et al., 2012).

A short construction schedule limits the financial cost escalation during the construction period. During construction, when no revenues allow the capital repayment, financial interests are compound over a growing invested capital base, increasing exponentially. This is the reason why, assuming the same total overnight construction cost as large units, multiple SMR projects pay lower IDC than LR projects (Carelli et al., 2007b; Boarin et al., 2012).

Shorter PBT of each SMR unit allows to get a cash in-flow from the sale of power generated by early units. Average outstanding capital exposure may be relieved by suitable staggered deployment of successive units, and cash flow from early units may be employed to finance the construction of later units on the site. This capability to self-generate the sources of financing is not available to a single large NPP project
and is a valuable option to limit up-front capital requirements: the relevant share of total capital investment cost may be provided by self-financing (Figures 10.15 and 10.16).

SMRs’ investment scalability is a key value driver: by staggering the investment effort over time, the average capital-at risk and IDCs are decreased. Cash out-flow profile during the construction phase is smoother for SMRs (Figure 10.17). These features make of SMRs an affordable investment option by investors with financial constraints, despite the conservative assumption of higher total capital investment cost.

The ALM process can provide a number of advantages, both business and technical, over traditional manufacturing methods. The justification for considering ALM arises from the volume of the market. For a small reactor with product lifespans of 40 to 60 years it is clear that no single supply chain can support the surge of production volumes at product launch and then sustainment for replacement parts towards the tail end of the product life with the same supply chain. This again is a new challenge for the nuclear industry that has evolved around a culture of bespoke engineering, where support for a plant through life from the same bespoke supply base is acceptable. For a small reactor delivered as a volume product the sustaining engineering challenge to the manufacturing supply base is different. Sustaining the product through life can no longer use the same original equipment manufacturer (OEM) supply chain economically. Automotive manufacturers do not supply replacement door panels for 10-year-old vehicles using the same line that delivers for their current year models. The small reactor supply chain faces the same set of challenges. Techniques such as ALM that have lower volume applications come into play offering significant economic advantages over the initial OEM supply chain. This is part of a strategy to maintain the competitive support of the plant through its operating life.

More specifically the attributes of ALM can be considered as two groups, OEM benefits and through-life benefits. ALM-OEM benefits include the following:

• Unit and/or through-life cost saving from reduced material quantity and/or machining costs offered by the ALM process.

• Unit and/or through-life cost savings from a reduced part count, e. g. manufacturing an assembly of multiple parts as a single component.

• The availability of welding test pieces, non-destructive examination (NDE) test pieces and other assembly and manufacturing aids significantly ahead of lead units can greatly reduce development programmes.

ALM — through-life benefits include the following:

• ALM can provide an alternative strategic sourcing route to the traditional forging, casting or fabrication route. It is highly suited to the low-volume, high-quality requirements of supplying nuclear-grade components. It can therefore be used to mitigate the risk of an existing manufacturing route that is threatened and/or may not be viable in the future for through-life sustainment.

• Where the existing manufacturing route is causing significant difficulties in supporting build, due to length of the manufacturing timescales.

By manufacturing components in layers, geometries that could not previously be

manufactured can now be produced. This enables a number of potential benefits:

• Optimisation of design definition for improved performance.

• Assemblies can be consolidated into a single component, thus simplifying manufacturing processes, reducing through-life costs, removing welds and fabrication, reducing inventory.

• Multi-functional parts can be produced by integrating cooling channels, electrical controls and instrumentation and/or cable management channels within structures.

• A structural integrity improvement may be realised, e. g. elimination of welds.

• High stiffness to weight ratio parts can be manufactured with internal lattice structures driven by finite element analysis (FEA) optimisation algorithms. These structures have thicker lattices where loading is high and thinner lattices where loading is low.

• Graded structures can be produced, where the material type is varied within a single structure, e. g. a tube can be manufactured that is Type 316L stainless steel at one end and Inconel 625 at the other, without the need for a transition weld.

12.3.1 Electron beam melting (EBM)

Additive manufacture by electron beam manufactures parts by melting metal powder layer-by-layer using an electron beam in a high vacuum environment. Parts produced by electron beam melting (EBM) are usually smaller than those produced by the laser process, but the EBM process does yield components that are fully dense, void-free and extremely strong.

As with ALM, CAD geometry, a power source and metal powder is required. However unlike ALM, EBM-fabricated components do not require heat treatment because of their high densification and operating temperature of typically 700-1000 °C during the fabrication phase. EBM is used in the aerospace sector where titanium and titanium-alloy components are produced, although systems do exist which can produce components up to 450 mm X 100 mm X 100 mm in a small variety of high — value metals.

Nuclear component materials in nickel-based alloys could be manufactured by the EBM process, but a cost-benefit analysis should be made to determine the viability when compared to existing fabrication techniques.

Synthetic gasoline (syngas) may be produced from natural gas or coal via the conventional methanol-gasoline process. These processes produce methanol as an intermediate product, synthetic gasoline and liquefied petroleum gas as end products, and significant GHG emissions. The conventional coal and natural gas cases differ in the approach to generate syngas; however, from the syngas to gasoline via methanol production, the processes are the same.

The nuclear heat integration cases for methanol to gasoline are slightly different in their integration points for the coal and natural gas feedstocks. For the coal-to — gasoline process, hydrogen from nuclear-driven HTSE is used in the gasification process. Power from the reactor is used for compression and sulfur removal. For the natural gas-to-gasoline process, nuclear heat is used for the reforming process and electric power is used for compression. Nuclear integration provides significant reduction in carbon dioxide emissions relative to the conventional (non-nuclear) case [3, 21, 22]

A performance test of the major components such as the RCP, steam generator (SG), and control rod drive mechanism (CRDM) was carried out. In the SMART standard design approval program, additional performance tests for the RCP and CRDM are scheduled to be performed to verify the final design models.

Figure 15.2 Schematic diagram of the VISTA facility.

Current large PWRs utilize two to four separate large steam generators; one in each coolant loop. These steam generators are either U-tube or once-through type heat exchangers. In either case, the higher pressure primary water flows inside the steam generator tubes and the lower pressure secondary fluid is outside the tubes. In the U-tube steam generator design, dry slightly saturated steam is delivered to the turbine generator. In the once-through steam generator design, super-saturated steam is delivered to the turbine generator (NRC, 2006).

Current steam generators range up to 70 feet (21 m) tall and contain 3000 to 16 000 tubes welded to a tube sheet. The steam generator tube sheet and tubes are part of the RCS boundary. A steam generator tube rupture provides a short circuit path for primary coolant to escape containment with the secondary fluid (NRC, 2009). Steam generator tube issues include tube denting, wastage, thinning, corrosion, flow — induced vibrations, cracking and deformation of U-tube bend or of support plates, tube leakage and fractures (Bonavigo and De Salve, 2011).

The active iPWR designs that are the most developed are planning one of two principal steam generator heat exchanger designs. The least traditional iPWR heat exchanger design is a once-through helical coil steam generator. The second iPWR heat exchanger design is a once-through straight-tube steam generator. No iPWR vendors have publically indicated an intention to use a vertical U-tube type steam generator, which will eliminate the most significant current steam generator tube concerns regarding cracking and deformation of the U-tube bend. Helical coil steam generators provide additional heat transfer surface in a limited amount of space and the helical fluid flow generates less flow-induced vibration. Helical coil steam generators also reduce thermal stress on the feedwater and steam headers generated by thermal expansion of the tubes. Likewise, there is little flow-induced tube vibration in once-through straight-tube steam generators. Therefore, fewer tube supports would be required, which limits low fluid flow areas and the associated corrosion concern.

However, once-through straight-tube designs do generate larger thermal stress on the feedwater and steam headers due to thermal expansion of the tubes. Helical coil steam generators will likely be more costly to produce than once-through straight-tube steam generators because of the increased complexity of the design, but the cost and complexity may be worth the reduction in stress on the steam generator headers and the increase in heat transfer area compared to the once-through straight-tube steam generator design.

Variations on implementation of these designs exist. For example, the NuScale iPWR design plans to utilize two separate but intertwined helical coil steam generators with the high pressure primary fluid outside the steam generator tubes and the lower pressure secondary fluid inside the steam generator tubes (NuScale, 2012). The SMART iPWR is designed for eight separate mini helical coil steam generators in the downcomer space around the reactor pressure vessel riser section (Lee, 2010). Likewise, the CAREM iPWR is designed for 12 separate mini helical coil steam generators in the downcomer space (Mazzi, 2011). The SMART iPWR and CAREM iPWR utilize a more traditional design approach with the primary fluid inside the steam generator tubes. All three of these designs will produce superheated steam.

The Generation mPowerTM is currently designed for a single once-through straight — tube steam generator that completely surrounds the central riser section. The primary fluid will flow inside the tubes and the secondary fluid will flow in the shell. The secondary fluids will enter and exit low in the steam generator shell; superheated steam will be produced (Kim, 2010). The Westinghouse iPWR design will also use a single once-through straight-tube steam generator that completely surrounds the central riser section. However, in this application a separate steam drum, outside the reactor pressure vessel, will be used to remove entrapped moisture in the steam. Dry steam with minimal moisture content will be delivered to the turbine generator instead of superheated steam employed in other iPWR designs (Memmott et al, 2012).

The Holtec SMR-160 uses a steam generator and superheater that are directly flanged to the top section of the reactor pressure vessel. This has the advantage of providing more direct access to the reactor fuel during the refueling process. The Holtec design plans to exchange reactor fuel in a single cartridge replacement (Oneid, 2012).

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)

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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.

The HSI in older NPPs has always been a reasonably complex system, but it was possible to describe it in fairly simple terms as consisting of control boards, panels, gauges, controls and alarm annunciators. However, with increasing automation

and availability of digital I&C systems, the HSI in newer NPPs has also become progressively more complex. The HSI is now a system with many functions, components and interfaces to other systems and environments. Even a superficial review of its many components will show that the HSI is in fact not only a hierarchy of high — and low-level components, but many of the components at the same level are linked in some way. It is also possible to describe this structure from different viewpoints, depending upon, for example, whether it is a safety — or non-safety-related system, whether it is used in operations or in maintenance, and so on. It is also possible to describe it as either an abstract functional or a physical structure.

Because it is easy to get lost in this complexity, an HSI architecture or taxonomy is proposed to guide I&C designers and human factors engineers in their analyses and designs. The easiest way to do this is to provide a reference table that illustrates the various levels of the HSI architecture and the relationships between them.

Tables 7.1 and 7.2 illustrate the distinction between the functions of the HSI and its physical architecture. The physical architecture consists of the concrete components, which include the operating environment (control rooms and other workspaces described in Section 7.7) and all the hardware within it. These physical components in turn make it possible for the operating crew to perform all tasks in the work environment. All of these components could be broken down to several levels of decomposition.

The taxonomy also indicates the operator task support components and functions. The implementation of such functions is a subsystem that does not exist in current NPPs, but it is included here because it is likely to be an important area of research and development over the next 10-20 years.

The physical HSI architecture includes the physical workspaces (control rooms and other work areas) and the devices within those areas. Table 7.2 shows first the typical structure of the MCR with the HSI contained within it, and then the other areas where humans may interact with a range of devices. Note that the ‘Safety provisions’ and ‘Environmental Control’ for the remote shutdown facility in Table 7.2 include provisions for habitability and survivability, such as battery backed-up HVAC, communications and personal protection equipment (PPE). The table does not show lower-level components for the outage management centre, engineering room, TSC and EOF, but they are listed to indicate other areas outside the MCR that operators interact with during different operational, maintenance and emergency conditions (see also Section 7.7).

As mentioned before, this architecture is not definitive and could be structured and described in a number of different ways. This is presented as a starting point for engineers and designers involved in the definition of I&C and HSI requirements.

The process of framing an evaluation requires close interaction between the analysts and the sponsors to specify the scope, particularly the system elements (facilities, processes, materials) and the range and definition of threats. The institutional context in which safeguards and other international controls would be implemented (national and international safeguards requirements and regulatory guidance, etc.) must also be specified in sufficient detail.

The process allows for evaluation to be performed at many levels, depending on the sponsor’s needs. From pre-conceptual design to a fully operational facility, the evaluation can and must become progressively more detailed. Timeframe can also dictate the depth of analysis; quick and coarse evaluations may be needed when answers are required within weeks or months and, for some problems, potentially even sooner. Such shortcuts, however, entail a higher degree of uncertainty in the results.

Most SMR designs are intended to use multiple modules at one site as a complete ‘reference’ application of the technology. These designs also contemplate the control of multiple reactors from one control room. Current US NRC requirements for operator staffing outlined in 10 CFR 50.54(m) prescribe the number of operators required for each unit and for each control room. As an example, for three operating nuclear power units at one site, NRC regulations and guidelines assume there are at least two control rooms and a total of eight licensed operators. These requirements are based on the operation of a large LWR. They are not based on new SMR designs that are safer and simpler in operation and shutdown mode. Also, the regulation does not address a situation where three or more units are controlled from a single control room.

The NRC staff reviewed pre-application submittals from SMR vendors on operator staffing. The staff considered proposed operator staffing based on control room designs and new technologies, proposed human factors and instrument and controls, and proposed research and development in this area (both by the domestic and the international community) to resolve the issue. In SECY-11-0098 (22 July 2011), the NRC staff recommended a two step approach to this issue: (1) in the near term allow SMRs to deviate from current staffing requirements through the exemption process, and (2) conduct further assessments and propose revisions to NRC staffing requirements based on human factors engineering (HFE) analysis of staffing needs and design. Some international SMR applications are considering remote operation of a reactor from a considerable distance. This application is not considered in this chapter since the type of SMR that might support remote operation is not being considered for near-term licensing and deployment.