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# Digital Instrumentation and Controls Research

The U.S. Nuclear Regulatory Commission (NRC) Office of Nuclear Regulatory Research (RES) performs research related to tools, methods, procedures, acceptance criteria, and guidance to assess the safety and security of digital instrumentation and controls (DI&C) systems in the U.S. nuclear industry.  RES provides technical information to support licensing decisions and prepares for the future by evaluating the safety implications of new technologies and designs.  RES coordinates research and development activities with other NRC offices and external stakeholders (e.g., universities, national laboratories) to address DI&C issues and support the use of consensus standards.  RES collaborates research efforts domestically and internationally to support the sharing of issues encountered and resolution devised in other regulatory environments.  RES’ collaboration extends internationally, including sharing operational experience data and developing analysis techniques.

Following are summaries of past and ongoing research grouped by topics, as follows:
        - Safety of DI&C Systems
        - Risk Quantification and Risk-informing
        - Embedded Digital Devices and Emerging Technologies
        - Environmental Effects
        - Online Monitoring
        - Wireless Technologies
        - Cybersecurity of DI&C Systems

Since 1993, research on the safety and security of DI&C systems has influenced regulatory practice. Notable examples include providing the technical basis to support BTP 7-14, BTP 7-19, standard review plan chapter 7 sub-chapter 9, Appendix 7-A in the Design-Specific Review Standard (DSRS) for small modular reactors, and revision 3 of the chapter 19 of the standard review plan (SRP-19), Section III Design-Specific probabilistic risk assessment (PRA) (Procedures for Specific PRA Audit Topics).  See Figure 1.  RES also assisted with development of Regulatory Guide 5.71 to pilot the implementation of 10 CFR 73.54.

*Figure 1: Research contributions to support licensing activities*

## Safety of DI&C Systems

Past research has included characterizing failure and fault modes and mechanisms, analyzing operational experience, risk informing the safety evaluation process, methods to test software, method to perform and evaluate a DI&C hazard analysis, and emerging technologies such as embedded digital devices. Ongoing DI&C systems safety research topics include common-cause failure, risk-Informed reviews, assurance case approaches, and causality-based techniques for performing hazard analysis and learning from events encountered during operation.

To learn from experiences outside of the commercial nuclear power industry, such as defense, space flight, commercial aviation, medical devices, automobiles, telecommunications, and railways, NRC has engaged with experts outside the NRC and continues to elicit knowledge from experts with safety-critical software and systems research experience in non-nuclear application domains.  The NRC coordinates research with the Electric Power Research Institute (EPRI) under a Memorandum of Understanding for exchanging technical information.  International collaboration includes the OECD/NEAHalden Reactor Project ‒ now focused on the Human, Technology and Organization (HTO) aspects. The NRC has hosted many Halden workshops to learn about the common needs and issues experienced by industry and to learn about best practices and the state-of-the-art in DI&C safety assurance, including a series of six workshops in 2020.

Uncertainties in the assurance of DI&C systems for safety functions in a variety of application domains are increasingly emanating from systemic causes. Many of the challenges experienced in the licensing reviews were rooted in hazards from systemic causes. Table 1 summarizes the research performed to address these uncertainties, obtain risk insights, and provide decision support for safety evaluation.

*Table 1: Decision support for Safety Evaluation of DI&C Systems: Uncertainties; Risk Insights*

*Figure 2: Major sources of uncertainty in the assurance of a DI&C system design (source: RIL-1001*

## Risk Quantification and Risk-informing

The current I&C regulatory infrastructure is based on compliance with the Institute of Electrical and Electronic Engineers (IEEE) design and quality standards and the NRC's defense in depth policy. The NRC staff routinely applies engineering judgment, e.g. on safety importance, and operating experience, in evaluating individual designs against regulatory standards. The NRC seeks additional technical methods and tools to better quantify risks and integrate risk insights into technical reviews and inspections of digital systems, consistent with the principles defined in Regulatory Guide (RG) 1.174 and other relevant guidance. Table 2 summarizes the research, spanning almost two decades, to quantify the risk contributed through software.

*Table 2: Safety of DI&C systems – Quantifying software contribution to risk*

## Embedded Digital Devices and Emerging Technologies

Embedded digital devices (EDDs) and related emerging technologies may introduce new hazards or other safety concerns, as presented in Regulatory Issue Summary 2016-05, "Embedded Digital Devices in Safety-Related Systems," dated April 29, 2016.  Table 3 summarizes research reports on these topics. Ongoing research aims to develop the technical basis for evaluating EDDs and emerging technologies, along with relevant observations, based on their classification, functionality, configurability, consequences of failure, and potential for common-cause failure (CCF). This research reviews how other agencies worldwide, both nuclear and non-nuclear, regulate, approve the use of, and apply EDDs.

Areas of interest include the types of components in safety-related applications most likely to have EDDs, methods used by other industries and countries to regulate the use of EDDs, and potential issues noted in industry. This information serves to support the technical basis for a graded approach in the selection and use of EDDs. A tangential supply chain issue is the use of replacement parts or parts in upgrades that may contain an undeclared digital device, as it may not meet the requirements for the safety-related application in which it is being used.

Other attributes such as reliability (the ability to perform with correct, consistent results), diagnostics, operating experience, and failure modes were reviewed because of their use in risk informing the acceptance of the use of EDDs. Emerging technologies associated with EDDs were noted during this work and are described. Table 3 summarizes research concerning EDDs.

*Table 3: Embedded digital devices, including Emerging Technologies associated with EDDs *

## Environmental Effects

This research addresses the effects of fire, smoke and other environmental effects on equipment.  Fire is a design-basis event. To demonstrate that it can be handled, licensees perform a post-fire safe-shutdown analysis to assure that a train of shutdown structures, systems, and components remains free of fire damage for a single fire in any single plant fire area.  Industry has developed methods for evaluating the effects of fire-induced circuit failures on safe-shutdown capability.  Nuclear Energy Institute report NEI-00-01, Revision 2, "Guidance for Post-Fire Safe Shutdown Circuit Analysis," May 2009, provides one acceptable method for performing a post-fire safe-shutdown circuit analysis when used with RG 1.189, Revision 3, "Fire Protection for Nuclear Power Plants," issued February 2018.

The NRC has sponsored research to support the development of the agency position in this area.  Table 4 summarizes research concerning effects of fire-related (e.g., smoke, heat) environmental conditions. 

*Table 4: Smoke and other environmental effects on electronic equipment*

Electromagnetic pulse and space weather effects: RES has examined the impact of electromagnetic pulse (EMP) on U.S. nuclear power plants since the 1980s.  RES continues to monitor developments in this area and update the findings periodically, expanding the scope to include space weather events.  Research efforts support the NRC position that U.S. plants can safely shut down in the aftermath of either occurrence.  The NRC is currently participating in the interagency response to Executive Order (EO) 13865, “Coordinating National Resilience to Electromagnetic Pulses.”  This is a government-wide effort to ensure national infrastructure components will remain functional in the event of an EMP.  Table 5 summarizes research concerning electromagnetic effects.

*Table 5: Electromagnetic Effects on Digital Electronic Equipment*

## Online Monitoring

Online monitoring refers to automated techniques used to assess instrumentation performance or health while the facility is operating.  Online monitoring seeks to determine whether the equipment has encountered an anomaly or fault or if recalibration is needed.  For example, some systems can detect an eventual bearing failure in a pump by monitoring vibrations; other systems are capable of monitoring safety signals when a protection channel is drifting out of the allowable tolerance.

The availability of online monitoring may result in licensees seeking approval to change surveillance and maintenance practices at nuclear facilities.  For this reason, the NRC proactively seeks to ensure that it is prepared to evaluate, provide timely decisions, and offer regulatory guidance on the safe use of online monitoring methods. Table 6 summarizes online monitoring research.

*Table 6: Online Monitoring*

## Wireless Technologies

The nuclear industry has expressed interest in expanding the use of wireless technologies in Nuclear Power Plant applications. Examples include use in industrial control systems (ICS) and data acquisition monitoring systems for plant component/equipment health monitoring that are located near, or even on, safety related/ important-to-safety (SR/ITS) equipment. Expansion of wireless technology use must ensure it does not impact safe operation of the plant through adverse interactions with SR/ITS systems. Table 7 summarizes research concerning Wireless Technology.

*Table 7: Wireless Technology including Emerging Technologies*

## Cybersecurity of Digital I&C Systems

Following the terrorist attacks on September 11, 2001, the NRC issued a series of security advisories and orders requiring nuclear power plants to take actions to enhance the protection of certain computer systems at nuclear power plants.  In 2009, the NRC issued Title 10 of the *Code of Federal Regulations*(10 CFR) 73.54, "Protection of Digital Computer and Communication Systems and Network" – also known as the cybersecurity rule. It is a performance-based programmatic requirement to ensure that digital computers, communication systems, and networks, associated with a nuclear power plant's safety, important-to-safety, security, and emergency preparedness functions are protected from cyber-attacks. In support of 10 CFR 73.54, the NRC published Regulatory Guide (RG) 5.71, "Cyber Security Programs for Nuclear Facilities," in 2010.  Table 7 summarizes research on cyber security of DI&C systems.

RES continues to support the review of the revision to RG 5.71, to ensure that DI&C systems can maintain safe operating environments in nuclear facilities.  RES also engages with the U.S. Department of Energy and the Electric Power Research Institute to coordinate and collaborate on future research in cyber security. Ongoing research includes security of wireless technologies in DI&C systems and assessment of emerging methods to assess security in a risk-informed manner.  RES also participates in governmentwide, academic, and industry working groups that provide the latest information and tools to address cyber threats.

*Table 8: Cyber Security of Digital I&C Systems*

Page Last Reviewed/Updated Wednesday, December 1, 2021

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Page Last Reviewed/Updated Wednesday, December 1, 2021