EPRI Bridges Industry R&D Gaps

By Arshad Mansoor, Electric Power Research Institute

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The technologies used to generate and distribute electricity will be radically transformed during the coming decade. Amid that change, the power industry must continue to meet customer reliability, safety, and cost-of-service expectations. Achieving the right balance among these often-conflicting goals is the primary focus of every utility. The Electric Power Research Institute is helping utilities achieve that balance with R&D programs for many new and emerging technologies.

The Electric Power Research Institute (EPRI) is an independent research and development (R&D) organization focused on solving the power industry’s most challenging technology, system reliability, environmental, and safety problems. In addition, EPRI provides direction and research support for emerging technologies of interest to the industry. EPRI members generate more than 90% of the electricity produced in the U.S., and international membership extends to 40 countries.

EPRI’s goal is to develop a comprehensive vision—broadly shared within the electricity sector, as well as by its stakeholders—of the innovations necessary to realize the industry’s opportunities and develop a comprehensive plan to overcome the associated challenges.

EPRI is working closely with more than 1,400 industry and public advisors and its Board of Directors to bring that vision to life. It has identified six key innovation and research paths that address both the opportunities for and challenges to the continued delivery of reliable, affordable, and environmentally responsible electricity: Long-Term Operations, Near-Zero Emissions, Renewable Resources and Integration, Water Resource Management, Energy Efficiency (End-to-End), and the Smart Grid. Included in the discussion below of each category are descriptions of several interesting projects and a short project status report.

Long-Term Operations

Long-term operations (LTO) research seeks to maximize the substantial value of existing generation, transmission, and distribution (T&D) assets. Obtaining the maximum operational lifetime from current assets will provide an essential economic buffer in the utility planning process. For example, high capacity factors and low operating costs make nuclear power plants some of the most economical, reliable, and environmentally responsible power generators available. Similarly, reliable, long-term performance of current fossil generation and T&D assets is essential to achieving a stable transition to a future electricity supply system.

Protect Nuclear Plants from Cyber Attack. In 2010, various media outlets reported that a computer worm called “Stuxnet”—designed to hijack control systems—had infected an Iranian nuclear fuel enrichment facility. This potential vulnerability highlights the need for more safeguards as nuclear plants replace old analog electronics-based instrumentation and control (I&C) systems with programmable digital systems. In October 2010, EPRI released a cyber security guideline that will help nuclear plant managers ensure that new digital systems comply with federal regulations designed to keep nuclear reactors safe from cyber attacks.

Cyber security is not a new concern. In the wake of the 2001 terrorist attacks, the U.S. Nuclear Regulatory Commission (NRC) mandated that nuclear power plants consider cyber security threats that could expose the public to radiation. The NRC also requires nuclear plants to maintain grid reliability. Therefore, the EPRI guideline also addresses systems that, if hacked, don’t directly pose a radiological risk, such as balance-of-plant control systems.

EPRI’s cyber security guideline provides procedures for implementing cyber security controls in 138 different areas, from passwords and wireless connections to encryption and intrusion detection. The document also provides four increasingly complex examples of how to apply the procedures in an operating nuclear plant. The examples range from a simple, firmware-based programmable relay without digital connections to other systems to a main turbine generator control system with digital assets both in the control room and on the turbine floor. Although demonstrating compliance with all controls requires extensive documentation, many controls can be addressed with existing plant programs such as the design change process and configuration management program. Plant owners and operators who incorporate cyber security into the design process early can make the final assessment of digital systems a much simpler process.

Because a variety of cyber security recommendations already exist, instead of developing controls and procedures from scratch, EPRI researchers built on existing guidance. The EPRI guideline can help plant managers prepare for that assessment and ensure a reliable transition to new digital I&C systems. This year, the team will release a training module outlining how to use the guidelines. The training will provide a brief, multimedia overview of the guidelines and procedures.

Monitor Equipment Health. EPRI has established proof of concept on the use of transient analysis methods for detecting indicators of performance degradation and incipient failure in electric motors and pumps before traditional online monitoring techniques can detect such degradation. Ongoing research is creating a generic methodology for health monitoring during startup and other transients to enhance prognostics, condition-based maintenance, and failure prevention for power plant equipment. Initial development is focused on electric motors, with field testing scheduled for 2012.

Current equipment-monitoring techniques, including advanced pattern recognition, continuously process steady-state sensor data to look for anomalies that may represent precursors of degradation, aging, and failure. However, components often don’t fail during steady-state operation, but during startup, load change, and shutdown cycles, when they are under more stress. Traditional monitoring techniques cannot easily detect anomalies during transient operation. In 2010, EPRI initiated exploratory research to determine whether certain failure precursors may be stronger—and more easily detected—during transients as opposed to during normal conditions.

EPRI assessed existing mathematical methods and algorithms that could be adapted to transient analysis for a variety of high-value components, such as electric motors, electric pumps, and steam turbine generators. Then, in proof-of-concept work at the University of Tennessee, data collected during previous run-to-failure tests of electric motors were analyzed using transient feature extraction techniques.

The EPRI study identified key transient data, including electrical, speed, and vibration signals, and developed prototype prognostic models. Notably, aging-related changes and performance degradation not detectable in high-speed motors under steady-state conditions were shown to be clearly evident in startup data. As a result, pertinent insights on remaining useful life and time to failure were available sooner than is possible using conventional methods.

Current EPRI research is creating transient analysis methods and models for online monitoring using real-time operating data from laboratory-scale motors and pumps. Once the methods are developed and host plants are identified, field testing of the transient analysis toolkit will begin in 2012 on full-scale, in-service components. Commercial vendors are expected to apply this novel prognostic approach to improve anomaly detection and remaining life assessment for a range of power generation and delivery system components.

Laser Welding for Nuclear Repairs. As nuclear reactors age, more neutrons are generated, and transmutation of elements occurs in the reactor internals and reactor pressure vessel. This increased “neutron flux” gradually increases the helium level in reactor internal components and reduces the material’s weldability via helium-induced cracking. The extent of cracking is heavily dependent on the heat input used for welding.

One area susceptible to such cracking is the riser brace attachment in boiling water reactors. Conventional arc welding techniques typically are not viable for repairing such components because their high heat input (millions of watts) would result in too much heating of the base metal. In contrast, laser welding, which operates at energy levels of only about 800 watts, provides the precise heat input control needed to avoid helium-induced cracking and excessive weld metal dilution. In addition, solid state laser technology is particularly promising for repairing reactor internals because it can be delivered to remote locations via optical fiber.

EPRI has been evaluating laser welding for several years, and for a variety of applications. Initial research focused on weld overlay of cracked components. Utility interest ultimately led to the first known application of laser technology in a nuclear setting: Eskom’s Koeberg plant in South Africa used laser welding in 2010 to mitigate through-wall cracking in an outdoor stainless steel storage tank. In early 2011, EPRI’s Welding and Repair Technology Center acquired and installed a 2-kW fiber laser system. A fiber laser is a compact, high-powered device that delivers a laser beam through an optical fiber, providing focused energy control.

An essential element of the research program will be to demonstrate the ability of laser welding to successfully repair irradiated material samples. Although EPRI can do much of the research to assess the process viability of the laser welding approach, full commercial viability can only be obtained using irradiated materials from a test reactor. EPRI is collaborating with the U.S. Department of Energy (DOE) to evaluate a hybrid laser welding process for repairing highly irradiated materials under EPRI’s Long-Term Operations Program and the DOE’s Light Water Reactor Sustainability Program. In addition, EPRI and the DOE are constructing a hot cell at Oak Ridge National Laboratory that will perform welding experiments on irradiated materials used to construct reactor internals and vessels.

Assess Concrete Integrity. Concrete is a key element in the reliable generation and delivery of electricity, and is found in everything from cooling towers to used fuel storage facilities and transmission infrastructure. The material is generally resistant to aging, becoming stronger over time as it cures. But high temperatures, freeze-and-thaw cycles, and exposure to radiation and chemicals can damage even the sturdiest concrete structures. Not every sign of wear and tear is visible, so EPRI is working to develop tools that can help see flaws deep inside a structure without damaging it—so-called nondestructive evaluation (NDE) methods.

NDE tools exist for other materials, such as metals. However, seeing inside concrete without damaging it is especially difficult because the material is a heterogeneous mix that varies with the composition of the local aggregate used. As plants apply to extend their operating licenses beyond 40 years, the need for new tools to test the integrity of dry cask storage containers, used fuel pools, cooling towers, containment buildings, and other structures will grow. Several NDE techniques have already been developed, and EPRI is working to design new ways of detecting and characterizing potential damage.

In 2011, EPRI installed fiber-optic strain gauges on some concrete structures at Ginna Nuclear Power Plant in upstate New York to measure real-time strain on the steel cables running through pre-stressed concrete. This included the concrete containment building. Engineers at Ginna periodically pressurize and depressurize the containment building to make sure it’s not leaking. During the most recent such test, EPRI researchers also measured the strain induced by such tests using digital image correlation.

In a separate project, EPRI engineers are examining how radiation can damage concrete in the reactor cavity’s walls and vessel supports, which may lead to the development of new NDE techniques to characterize such damage.

EPRI will be investigating how corrosive materials such as chlorides and boric acid affect concrete. Boric acid is found in used fuel pools at pressurized water reactors, and chloride damage can come from seawater or other sources. Researchers at the Materials Aging Institute in France—a collaborative R&D institute funded by EPRI, the French utility EDF, and the Japanese utilities Tokyo Electric Power Co. and Kansai Electric Power Co.—have already begun looking at the effects of boric acid on concrete. At the same time, the commercial sector is searching for new NDE methods to image voids, cracks, and other internal defects. The most promising techniques will likely be tested in the field in the next five years.