PNNL-22622, Rev. 1 SMR/ICHMI/PNNL/TR-2013/04 Prepared for the U.S. Department of Energy under Contract DE-AC05-76RL01830 Technical Readiness and Gaps Analysis of Commercial Optical Materials and Measurement Systems for Advanced Small Modular Reactors NC Anheier M Bliss JD Suter BD Cannon A Qiao R Devanathan ES Andersen A Mendoza EJ Berglin DM Sheen August 2013 PNNL-22622, Rev. 1 SMR/ICHMI/PNNL/TR-2013/04 Technical Readiness and Gaps Analysis of Commercial Optical Materials and Measurement Systems for Advanced Small Modular Reactors NC Anheier M Bliss JD Suter BD Cannon A Qiao R Devanathan ES Andersen A Mendoza EJ Berglin DM Sheen August 2013 Prepared for the U.S. Department of Energy under Contract DE-AC05-76RL01830 Pacific Northwest National Laboratory Richland, Washington 99352 Executive Summary This report supports the U.S. Department of Energy’s Office of Nuclear Energy (DOE-NE) Nuclear Energy Research and Development Roadmap and industry stakeholders by evaluating optically based instrumentation and control (I&C) concepts for advanced small modular reactor (AdvSMR) applications. These advanced designs will require innovative thinking in terms of engineering approaches, materials integration, and I&C concepts to realize their eventual viability and deployment. The primary goals of this report include: 1. Establish preliminary I&C needs, performance requirements, and possible gaps for AdvSMR designs based on best-available published design data. 2. Document commercial off-the-shelf (COTS) optical sensors, components, and materials in terms of their technical readiness to support essential AdvSMR in-vessel I&C systems. 3. Identify technology gaps by comparing the in-vessel monitoring requirements and environmental constraints to COTS optical sensor and materials performance specifications. 4. Outline a future research, development, and demonstration (RD&D) program plan that addresses these gaps and develops optical-based I&C systems that enhance the viability of future AdvSMR designs. The DOE-NE roadmap outlines RD&D activities intended to overcome technical barriers that currently limit advances in nuclear energy. As part of this strategy, DOE-NE is sponsoring research on advanced reactor supportive technologies to reduce the identified barriers. Key challenges that must be overcome include the high capital costs to develop nuclear power plants, maintaining safety performance as the reactor fleet expands, minimizing nuclear waste, and maintaining strong proliferation resistance. AdvSMR designs are a major component of this strategy, because these designs offer a number of unique advantages. The modular and small size of AdvSMR designs naturally lead to reduced capital investments and, potentially, construction savings through factory fabrication. However, new economic and technical challenges accompany the many attractive features offered by AdvSMR designs. Specifically, the modest power output of AdvSMRs does not provide the economy of scale afforded by large reactors. In addition, many of the AdvSMR designs operate at much higher temperatures than light- water reactors and require instrumentation to withstand harsh, in-vessel environments arising from unconventional, chemically aggressive coolants and unique reactor system configurations. Addressing these I&C challenges will be critically important to the AdvSMR development program to ensure the viability and future success of advanced reactor designs. Solutions will likely be found through evolution of conventional reactor technology, and the development of entirely new concepts. Early pressure/boiling water reactors used conventional I&C technologies (e.g., thermocouples, ion- chambers, strain-gauge pressure sensors) to satisfy design requirements. Because these technologies worked well in the relatively low-temperature reactor designs, the demand for alternate I&C technologies was limited. At the time, optical-based reactor monitoring concepts were generally dismissed because of a number of economic and technical limitations. Optical sensor systems were not cost-competitive or failed to offer superior performance compared to conventional reactor monitoring systems. Reliability and service performance were in question because there was only a basic understanding of the radiation damage mechanisms in optical materials. In other cases, computational systems did not exist or have sufficient power to support the processing needs of optical-based monitoring systems. This trend iii continued through the next several decades (i.e., 1960–1990s), as conventional I&C systems continued to offer acceptable performance. Conventional design rules are unlikely to hold for future advanced reactor concepts, because of the demanding design requirements. Thus, new approaches will be needed to support AdvSMR I&C requirements. Because significant technology advancements have been made in the past several decades, current optical-based sensing and interface technologies now may have an impact in this area. Key elements include advancements in optical sensing performance, precision component fabrication, laser technology, integrated optoelectronics, and advanced computer signal processing hardware and software. New optical materials and purification methods that incrementally improved material properties, leading to enhanced suitability for more challenging applications, have been developed. Significant optical materials research was conducted to gain insight into radiation damage and other performance issues. This research established the physical damage pathways and productive development areas to minimize vulnerabilities to radiation-induced damage. Most likely, further advancements in many optical materials and monitoring systems will be required prior to possible use in future AdvSMR designs. Because optical systems offer many unique advantages over traditional approaches, further study commensurate with the abilities of optical systems may be very fruitful. Key advantages provided by optical systems include: • Noncontact, standoff sensing and monitoring – Both passive and active remote sensing can be performed by many different optical sensing techniques. Standoff sensing can also help to isolate sensitive components from high temperatures and radiation exposure. Laser vibrometry is an example of noncontact, standoff optical monitoring. • Drift-free monitoring – Many optical sensing techniques are based on first-principle measurements and therefore are less susceptible to signal drift. Time-dependent drift is a common problem in thermocouples, which estimate temperature based on changes in junction voltage. Drift in thermocouples is distinguished by metallurgical changes in the junction electrode (e.g., oxidation, depletion, contamination, strain). In contrast, optical pyrometry measures temperature based on direct measurement of black body optical emission. • High bandwidth – High-bandwidth measurements and data transfer can be made in the optical fiber. High-bandwidth sensors are well suited for high-speed measuring applications. Frequency analysis techniques can be used to extract additional signal information, such as component vibration. Signal averaging of high-bandwidth measurements can improve the signal-to-noise performance. Optically encoded data can be transmitted at significantly higher data rates (i.e., > 100 Gb/s) compared to traditional electronic methods. • Multi-parameter measurements – The same sensor system can support different modes of parameter monitoring (e.g., visualization, flow, and vibration). For example, advanced image processing methods can be used to extract vibration information from camera video data. • Multi-mode measurements – The same sensor system can support different modes of operation (e.g., inspection, refueling, and processing monitoring). For example, camera systems can provide remote visualization of in-vessel processes (i.e., rod control motion) and servicing operations (i.e., robotic fuel handling). • Distributed sensing – Optical fiber Bragg gratings and time domain reflectometry sensors are well known distributed sensing systems. Using this configuration, a single optical fiber can monitor parameters of interest along the entire length of the fiber. iv • Integrated path length measurements – Optical sensing techniques can provide integrated path length measurements, which can be superior to point measurements. Parameter profiles are commonly estimated using discrete sensing points, such as multiple-temperature sensors positioned to estimate primary reactor outlet temperatures. A preferred method is direct-profile measurements using a single measurement sensor. Many optical systems can directly measure parameter profiles. For example, optical absorption spectroscopy can be used to measure chemical concentration profiles of trace headspace gases. Optical-based measurement and sensing systems for AdvSMR applications have several key benefits over traditional instrumentation and control systems used to monitor reactor process parameters, such as temperature, flowrate, pressure, and coolant chemistry. However, technical challenges exist in the areas of 1) optical access that enables in-vessel optical monitoring, 2) optical materials under extreme conditions, and 3) performance limitations of COTS optical monitoring technologies. This report proposes a comprehensive, multi-year RD&D plan to advance the concept of in-vessel optical monitoring and the technical readiness of COTS optical materials, components, and sensing instrumentation.