Abstract
Instrumentation, controls, and human-machine interfaces (ICHMI) are essential enabling technologies that strongly influence nuclear power plant performance and operational costs. The nuclear power industry is currently engaged in a transition from traditional analog-based instrumentation, controls, and human-machine interface systems to implementations employing digital technologies. This transition has primarily occurred in an ad hoc fashion through individual system upgrades at existing plants and has been constrained by licenseability concerns. Although the recent progress in constructing new plants has spurred design of more fully digital plant-wide ICHMI systems, the experience base in the nuclear power application domain is limited. Additionally, development of advanced reactor concepts, such as Generation IV designs and small modular reactors, introduces different plant conditions (e.g., higher temperatures, different coolants, etc.) and unique plant configurations (e.g., multiunit plants with shared systems, balance of plant architectures with reconfigurable co-generation options) that increase the need for enhanced ICHMI capabilities to fully achieve industry goals related to economic competitiveness, safety and reliability, sustainability, and proliferation resistance and physical protection. As a result, significant challenges remain to be addressed to enable the nuclear power industry to complete the transition to safe and comprehensive use of modern ICHMI technology.
The U.S. Department of Energy (DOE) has recognized that ICHMI research, development, and demonstration (RD&D) is needed to resolve the technical challenges that may compromise the effective and efficient utilization of modern ICHMI technology and consequently inhibit realization of the benefits offered by expanded utilization of nuclear power. Consequently, several DOE programs have substantial ICHMI RD&D elements within their respective research portfolios. This paper describes current ICHMI research in support of advanced small modular reactors. The objectives that can be achieved through execution of the defined RD&D are to provide optimal technical solutions to critical ICHMI issues, resolve technology gaps arising from the unique measurement and control characteristics of advanced reactor concepts, provide demonstration of needed technologies and methodologies in the nuclear power application domain, mature emerging technologies to facilitate commercialization, and establish necessary technical evidence and application experience to enable timely and predictable licensing.
1 Introduction
Instrumentation, controls, and human-machine interfaces are essential enabling technologies that strongly influence nuclear power plant performance and operational costs. The nuclear power industry is currently engaged in a transition from traditional analog-based instrumentation, controls, and human-machine interface (ICHMI) systems to implementations employing digital technologies. This transition has primarily occurred in an ad hoc fashion through individual system upgrades at existing plants and has been constrained by licenseability concerns. Although the recent progress in constructing new plants has spurred design of more fully digital plant-wide ICHMI systems, the experience base in the nuclear power application domain is limited. Additionally, development of advanced reactor concepts, such as Generation IV designs and small modular reactors, introduces different plant conditions (e.g., higher temperatures, different coolants, etc.) and unique plant configurations (e.g., multiunit plants with shared systems, balance of plant architectures with reconfigurable co-generation options) that increase the need for enhanced ICHMI capabilities to fully achieve industry goals related to economic competitiveness, safety and reliability, sustainability, and proliferation resistance and physical protection. As a result, significant challenges remain to be addressed to enable the nuclear power industry to complete the transition to safe and comprehensive use of modern ICHMI technology.
The U.S. Department of Energy (DOE) has recognized that ICHMI research, development, and demonstration (RD&D) is needed to resolve the technical challenges that may compromise the effective and efficient utilization of modern ICHMI technology and consequently inhibit realization of the benefits offered by expanded utilization of nuclear power. Consequently, several DOE programs have substantial ICHMI RD&D elements to their respective research portfolio. The objectives that can be achieved through execution of the defined RD&D are to provide optimal technical solutions to critical ICHMI issues, resolve technology gaps arising from the unique measurement and control characteristics of advanced reactor concepts, provide demonstration of needed technologies and methodologies in the nuclear power application domain, mature emerging technologies to facilitate commercialization, and establish necessary technical evidence and application experience to enable timely and predictable licensing. This article discusses the ICHMI RD&D being conducted under a key DOE nuclear power program. Specifically, the Small Modular Reactor (SMR) Program has a dedicated research pathway to address ICHMI issues.
2 Advanced SMR R&D program overview
The overall program for supporting the development, demonstration, and deployment of SMRs consists two distinctly different elements: the SMR Licensing and Technical Support (LTS) Program and the Advanced SMR (AdvSMR) Research and Development (R&D) Program. The SMR LTS Program focus is on certification, licensing, and deployment of the most mature light-water-cooled SMR designs (i.e., integral primary system reactors or IPSRs) through cost-shared partnerships with multiple reactor vendor/licensee teams. The AdvSMR R&D Program focus is on non-light-water-cooled high-temperature designs (e.g., liquid metal, fluoride salt, gas) with activities to provide for the development of next-generation, advanced SMR concepts. However, provisions to support resolution of lessons learned from the certification and first-of-a-kind deployment of near-term SMR designs are also in place. Thus, the AdvSMR R&D program is principally an objective and “technology neutral” endeavor placing no particular preference on a specific design.
The primary goal of the AdvSMR R&D Program is the demonstration and deployment of advanced SMR designs that can provide safe, simple, and robust sources of energy to meet expanding needs for electricity, process heat, or other applications at an affordable price, including developing advanced SMR concepts that can achieve significantly enhanced performance and utility for a broader range of energy applications and developing transformational technologies that will enable the next generation of SMR designs to be deployed by 2030. For these objectives, the AdvSMR R&D Program supports nuclear technology that enables the development and demonstration of new innovative SMR designs.
RD&D planning is guided by identification of technology gaps and challenges that could either inhibit the maturation of advanced designs or compromise the economic viability of SMRs as a class of plants. In addition, technology development opportunities that can facilitate improved economic competitiveness and enhanced safety are addressed as well.
Advanced SMRs face significant technical hurdles to design completion and commercialization due to the unique features and characteristics inherent to their compact designs. These features may include new fuels and materials of construction, tighter integration of primary system components within the primary system pressure boundary, the employment of modular fabrication techniques, or the use of long-life cores and advanced sensors and instrumentation.
3 DOE research on ICHMI technology for SMRs
The benefits of SMRs can include reduced financial risk, operational flexibility, and modular construction. Achieving these benefits can lead to a new paradigm for plant design, construction, and management to address multi-unit, multi-product-stream generating stations and to offset the reduced economy-of-scale savings. Fulfilling the goals of SMR deployment also depends on the resolution of technical challenges related to the unique characteristics of these reactor concepts. ICHMI technologies provide the foundation for what is the equivalent of the central nervous system of a nuclear power plant. Therefore, ICHMI RD&D can play a significant role in resolving challenges and realizing benefits specific to SMRs.
3.1 ICHMI research drivers for SMRs
ICHMI research drivers arise to resolve outstanding challenges and realize the prospective benefits posed by development and deployment of SMRs. These drivers translate into technology needs and innovation opportunities. The basis for identifying ICHMI challenges and the resulting RD&D needs can be categorized into three major elements. These three major elements are (1) ICHMI issues that arise from the unique operational and process characteristics that are the consequence of fundamental design differences between advanced SMRs and previous or current large plants, (2) ICHMI technologies that can ensure and then further enhance the affordability of SMR plants, and (3) ICHMI technologies that can further expand the functionality of SMRs.
3.1.1 Unique operational and process characteristics
Small reactors have different process measurement needs from large light-water reactors (LWRs). For advanced SMRs with different coolants (e.g., gas, liquid salt, liquid metals) operating at higher temperatures, the process measurement instrumentation needs to be both chemically compatible with the coolant as well as tolerant of the higher temperature. Similarly, diagnostic measurements are different for reactors with different coolants.
The unique operational characteristics of most SMR designs arise from the dynamic behavior of each general reactor class and differences in plant configurations. For SMR concepts that involve passive process systems, the impact of those systems on operability and plant performance needs to be evaluated to ensure proper consideration in control and safety requirements.
3.1.2 Affordability
Two factors for the economic competitiveness of SMRs that can be notably affected by design and implementation are the up-front capital cost to construct the plant and the day-to-day cost of plant management, including operations and maintenance (O&M). The former cost is primarily dependent on the size and complexity of the components that must be fabricated and the methods of installation. A simplified design, smaller components, and modular fabrication and construction are among the characteristics of SMRs that can reduce this cost.
However, reduction in cost for capital equipment tends to increase the significance of ICHMI costs, which do not tend to scale with size. Thus, effective use of advanced technology to minimize cable runs and consolidate functions in highly reliable systems can contribute to managing up-front costs for ICHMI. Selection of innovative technologies may also provide some benefit in reducing the fabrication, installation and inspection costs, financing costs, and O&M costs. The most significant controllable contributor to day-to-day costs arises from O&M activities, which are heavily dependent on staffing size and plant availability. Efficient, effective operational approaches and strategic maintenance can help contain these costs and ensure economic viability.
3.1.3 Enhanced functionality
SMR designs can provide the benefit of sustained output from a plant composed of multiple modules. By building a large power park of many SMR modules, the plant has the advantage of only losing a small percentage of its power output should one unit be out of service for a planned outage or unplanned trip. Effective plant management through advanced control and predictive maintenance capabilities enhances this benefit. The expected impacts are minimization of unplanned shutdowns and optimization of maintenance demands through condition determination (monitoring) and stress reduction (control).
3.2 Needs and challenges for ICHMI technology research
Based on consideration of the drivers related to the benefits and challenges of SMRs, corresponding technology needs and innovation opportunities are identified. The needs and opportunities identified for advanced SMR development and deployment that should be addressed through RD&D into ICHMI technologies can be organized according to four subactivity areas. Based on high-level technology groupings, these areas are defined as follows: Sensors and Measurement Systems, Diagnostics and Prognostics Methods, Plant Operations and Control, and ICHMI Architectures and Infrastructure.
Sensors and measurement systems present the primary source of technology gaps for advanced SMR concepts. There simply exist no viable, commercially available sensing capabilities that can directly measure some key parameters given the harsh environments, chemically different coolants, and unique configurations of many advanced concepts. Failing an advance in the technology, indirect measurements, with their attendant uncertainties leading to greater safety margins and less efficient operation, constitute the principal option, thereby limiting designs. Addressing the need for direct sensing capabilities can remove design constraints and enable improved efficiency while reducing the uncertainties built into margins.
Diagnostics and prognostics capabilities provide a technical means for enhancing affordability of SMRs over their lifetime. Advanced diagnostics and prognostic systems have the potential to reduce labor demands arising from currently required periodic equipment surveillance and inspection, thereby reducing manpower demands. Additionally, these systems can significantly reduce risks to safety and investment protection due to a greater understanding of precise plant equipment conditions and margins to failure. Also, development of diagnostic and prognostic methods allows evidence to be developed to support a science-based justification for extended plant lifetime.
Regarding plant operations and control, innovative concepts of operation and advanced human-automation collaboration are aspects of control room operations and human factors engineering that can contribute to enhanced affordability of SMRs through optimal performance and reduced O&M costs. Effective use of human resources based on advanced human-automation collaboration can enable O&M cost containment through reduced staffing requirements. In addition, control of SMRs will benefit from a high degree of automation to enable efficient operations while minimizing the need for a large operational staff. This is especially true for multiple SMR units in a multi-modular nuclear plant.
The fourth subactivity area addresses the infrastructure to support ICHMI technology development and the architectural elements that constitute the necessary plant ICHMI systems. Immediate development activities can provide tools for representing the SMR systems of interest and establish a common resource to facilitate an efficient RD&D program. Longer-term research addresses architectural innovations that enable needed capabilities (e.g., measurement, monitoring) to be implemented under adverse conditions (i.e., harsh environments) and within imposed application constraints (i.e., limited wired interconnections).
4 Conclusions
Energy security and the reduction of greenhouse gas emissions are two key energy priorities that can be met in a sustainable manner through nuclear power. The development of deployable small modular reactors (SMRs) can provide another economically viable energy option, diversify the available nuclear power alternatives, and enhance economic competitiveness by ensuring a domestic capability to supply demonstrated reactor technology to a growing global market for clean and affordable energy sources. Achieving these objectives requires technology development. As part of its research portfolio, DOE recognizes that ICHMI technology development is necessary to resolve impediments to the realization of SMR deployment.
A comprehensive SMR research effort addresses key needs and challenges to enable optimal technology solutions. In particular, technical advancements and demonstration of technological maturity must move forward to effectively realize the safe, economic, and effective deployment of SMRs. Consequently, the AdvSMR R&D Program is proceeding with a set of ICHMI research projects. Key RD&D areas include sensors and measurement systems, diagnostics and prognostics methods, plant operations and control, and ICHMI architecture (e.g., communications, power, interfaces, and shared components) and infrastructure. As noted, some RD&D drivers arise from the unique operational and process characteristics that are the consequence of fundamental design differences between SMRs and current large plants. Other ICHMI technologies must be developed to further enhance the affordability of new SMRs by achieving lower O&M costs by reducing staffing and maintenance requirements via innovative concept of operation strategies, intelligent human-system interfaces and functional allocation. The functionality of SMRs can be expanded through the development of advanced control capabilities that enable sophisticated operational approaches such as intelligent control to facilitate automated load following for multi-unit plants to offset the grid impact of intermittent power generators such as wind turbines or photovoltaic arrays.