A new series of Associated Press reports raising questions about nuclear power plant safety fails to acknowledge actions that the industry takes proactively to improve performance and address aging management and plant reliability issues.Over just the past four years, more than 20 of the Top Industry Practice awards presented to industry employees during the Nuclear Energy Institute’s annual conference in May have been for innovations that focus on aging management or long-term plant reliability. They are highlighted below.
• Tennessee Valley Authority (TVA) employees at the Browns Ferry nuclear energy facility in Alabama have been honored with the 2011 B. Ralph Sylvia “Best of the Best” Award for developing a state-of-the-art method to prevent reactor fuel rod defects. Using real-time stress monitoring of the sealed tubes that hold the uranium fuel pellets, a new methodology called XEDOR has proven highly effective.
Five years ago, the industry established a goal to eliminate by the end of 2010 fuel rod defects that could release radionuclides from fuel pellets. Some damage is caused by the interaction between fuel pellets and the metal tube material called cladding. The phenomenon can result in additional costs to utilities, affect plant operation and subject personnel performing repairs to additional radiation exposure.
Working with AREVA, the winning TVA team implemented a new methodology that performs real-time, online stress calculations for every six-inch fuel rod segment in all parts of the reactor core. It is the first method that can calculate how close fuel rods are to cladding damage, thus ensuring fuel integrity performance.
• Omaha Public Power District team members at Fort Calhoun Station in Nebraska garnered the 2011 Westinghouse Combustion Engineering Design Vendor Award by looking back 10 years to determine the future of critical metal components at their plant.
The Omaha Public Power District team devised a method to accurately track the development of microscopic “stress corrosion” cracking in nozzle welds for large pipes attached to the reactor vessel.
To achieve this technical advance, the team monitored surface changes of the metal over a 10-year period. By comparing the material condition and trending data, the team was able to determine the current status of the material, predict when granular cracking would take place and plan when to replace the components.
The team enhanced nuclear safety by monitoring the assurance of material condition of plant components and detecting flaws, thus lowering the probability of leaks and reducing worker radiation doses thanks to less frequent examinations. To date, their program has reduced expense for unnecessary nozzle replacements by more than $2 million.
• Exelon Nuclear employees at the LaSalle County power station in northern Illinois were awarded the 2011 GE Hitachi Nuclear Energy Vendor Award for collaborating with GE Hitachi on the design, construction, testing and installation of a digital Rod Control Management System that more precisely positions control rods and monitors their placement in the reactor.
The new integrated system displays a detailed map of the control rods with a digital touch screen. It has faster scan capabilities and retains information about control rods’ previous position.
The entire system was installed in just five days during a refueling outage at the LaSalle plant and has performed all control-rod manipulations. The system’s enhanced capabilities—including the ability to isolate rods for troubleshooting without affecting other rods—save maintenance resources and increase plant safety and efficiency.
• The 2011 Westinghouse Design Vendor Award was won by Southern Nuclear Operating Co. employees at the Farley nuclear plant in Alabama for their innovative reactor coolant pump shutdown seals that greatly reduce seal leakage and enhance safety at the plant.
Reactor coolant pump seals are necessary for safe operation of a pressurized water reactor to help prevent reactor coolant loss in severe events.
To combat the possibility of a loss of coolant accident, the winning team developed a first-of-a-kind shutdown seal called the Shield. The Shield is activated by heat and provides a leak-tight seal if cooling for the reactor coolant pump seals is lost. The design causes the seal components to constrict and reduce flow. The shield can be installed easily and does not require additional modifications to the reactor coolant pump.
• Exelon Nuclear employees at Byron power station in Illinois won the 2011 Equipment Reliability Process Award for their development of chemical injection during power operation that reduces iron buildup in heat exchanger tubes and helps maintain plant efficiency.
Iron can build up in the heat exchange tubes of the steam generators, reducing the efficiency of the transfer of heat and lowering power output by the plant. Injection of an iron dispersant into the water that goes through the heat exchange tubes slowed iron accumulation in the steam generators. The reduced need for tube cleanings lowers the radiation dose to workers who clean sludge deposits from the component.
• Duke Energy employees at the Oconee power plant in South Carolina earned one of two 2011 Maintenance Process Awards for improving automatic oilers for a large amount of rotating mechanical equipment.
Duke Energy developed a laser-guided handheld tool that is small, easy-to-use and inexpensive. The laser-guided tool ensures accuracy by generating a bright red line, which is projected onto the bearing housing to serve as a visual reference. Its ease of use means that the time required to check oil levels has dropped to about 30 seconds from five to 10 minutes.
Setting or checking oil levels with the new tool improves the reliability of rotating equipment. With millions of automatic oilers around the world in all industries, this new method is widely adaptable at nuclear energy facilities and other industries.
• Employees of American Electric Power at the Donald C. Cook Nuclear Plant in Michigan won the 2011 Plant Support Process Award for its comprehensive groundwater protection modeling software to maintain safety and enhance public confidence.
To enhance communications when there is leakage of tritium or other materials at plant sites, the winning team pioneered the use of comprehensive groundwater protection monitoring software. The software can display 3D modeling of the site’s systems, structures and components in relation to tritium leakage. The highly interactive software allows for vast amounts of information to be efficiently managed and easily interpreted. Most significant are its predictive and investigative abilities, which can identify the potential sources of a leak and the potential impacts it may have—information that can result in better public and environmental protection.
• Entergy Nuclear employees at the Palisades nuclear power station in western Michigan have been honored with the 2010 B. Ralph Sylvia Best of the Best Award for developing an innovative device that improves the quality of reactor vessel head inspections.
The device, called a gimbaled head, uses ultrasonic transducers to identify irregularities within the welded steel reactor vessel head nozzles used for control rod drive mechanisms and nuclear instrumentation. A vessel head is a massive, multi-ton component that helps house the uranium fuel assemblies that are the energy source for 20 percent of U.S. electricity supplies, as well as various instruments used to operate the reactor.
Previously, engineers at the Palisades plant needed four different kinds of testing devices to complete the inspection. The gimbaled head device performs the entire inspection, conducting an even more thorough, accurate and effective examination in less time. Additional improvements have enabled the ultrasonic transducers to produce higher quality and more consistent inspection information.
• Dominion Power employees at Virginia’s Surry power station collaborated with AREVA to win the 2010 AREVA Vendor Award for developing the Deposit Minimization Treatment process to decrease the buildup of sludge on the plant’s steam generator tubes.
Sludge buildup on the steam-producing side of the steam generator tubes had reduced steam pressure and could have affected power generation. The previous solution for cleaning such material from the tubes required harsh chemicals.
Dominion Engineering and Chemistry personnel developed a cost-effective and environmentally sound solution to eliminate the buildup and restore consistent power generation. The Deposit Minimization Treatment is a safer, simplified system that reduced deposits by 700 to 800 pounds and saved the company approximately $32 million. It does not require harsh chemicals, and waste from the process can be treated with filtration to decompose the active ingredient.
While the old system required that cumbersome equipment be connected to the steam generator in several places, the new system has smaller and fewer pieces and requires only a single connection. The equipment now can be placed in a remote location, eliminating the need for work within the reactor building and enhancing radiation safety and security. The process has application potential for other pressurized water reactors.
• FirstEnergy Nuclear Operating Co. employees at Beta Laboratory landed the 2010 Materials and Services Process Award for their success in upgrading integrated control system circuit cards to increase plant reliabilty. By developing an in-house solution based on manufacturing processes, the team enhanced the design and produced a more reliable circuit card while saving time and money.
Because integrated control system circuit card malfunctions can cause power reductions and other plant challenges, improved equipment reliability was also among the team’s top goals. The new circuit cards featured improved relay design and higher performance specifications, which enhances plant reliability and reduces the preventive maintenance needs of the plant.
All steps of the process were completed in-house including design enhancement, prototyping, manufacturing and assembly. The final step was a rigorous testing process conducted by a comprehensive automated program also developed in-house. The in-house solution upgraded a circuit card for eight percent of the cost of off-site manufacturing. This innovation saved more than $1 million and contributed to greater supply chain efficiency.
• Progress Energy employees at the Shearon Harris nuclear plant are recipients of the Vision & Leadership Award for their pioneering improvements in plant fire protection.
In 2004, the NRC approved use of the National Fire Protection Association’s performance-based standard. The Shearon Harris fire protection team has led the industry in implementing the standard, focusing on two actions in particular to improve fire protection.
First, because extreme heat can damage conventional cable, the team replaced vital and vulnerable cables with a fire-rated version that can withstand three hours of exposure up to 2,000 degrees Fahrenheit. The use of fire-rated cable in critical areas helps insure that the plant can be shut down safely in the event of fire.
Second, the team developed an early warning system that can detect fire-prone conditions before a fire can start. The new detection hardware combats fires by detecting precursor conditions. The system monitors critical equipment for signs of degradation and notifies operators so they can perform preventive maintenance before problems arise.
The Progress Energy team led the nuclear energy industry through this important strategic fire protection process. Their innovations will improve nuclear plant safety and produce significant savings across the industry.
• Employees of Omaha Public Power District at Fort Calhoun nuclear energy station have been honored with the nuclear energy industry’s 2009 B. Ralph Sylvia Best of the Best Award for developing a method to accurately assess the susceptibility of stainless steel and other alloys to stress corrosion cracking.
Untreated, stress corrosion cracking can weaken piping and other components. But the onset of stress corrosion cracking has been difficult to predict given that it can take 20 years or more to develop. Through extensive research, the OPPD team determined that eddy current testing, an electromagnetic process that can detect tiny flaws in metals, can accurately measure subtle changes on the inner surface of a metal component to determine if so-called “incubation” of this phenomenon is occurring at a microscopic level and, therefore, if the onset of stress corrosion cracking is imminent.
The initial area of concern at Fort Calhoun was in the housings that enclose the control rod drives within the reactor coolant system. Some housings were unnecessarily replaced because stress corrosion cracking was suspected, but was not actually present. By creatively using eddy current testing to accurately project the start of stress corrosion cracking, the Fort Calhoun team has helped avoid the unnecessary replacement of expensive plant components, saving money and significantly reducing radiation exposure to project teams. Since its inception in 1999, the eddy current testing program has saved nearly $7 million and 10 to 50 person-rem of combined radiation exposure to workers at Fort Calhoun. The Nuclear Regulatory Commission’s limit for radiation exposure to an industry worker is five rem per year.
• Employees of Exelon Nuclear at Pennsylvania’s Peach Bottom power station collaborated with Global Nuclear Fuel (GNF) to earn the 2009 GE Hitachi Nuclear Energy Vendor Award for their use of the Defender Debris Filter to prevent debris from entering and potentially damaging fuel assemblies. The Defender Debris Filter, developed by GNF, captures small segments of wire, metal shavings and the like that can lead to fuel rod damage.
Exelon installed the first Defender Debris Filters in Peach Bottom 2 in 2006, after debris-related fuel damage at two reactors there. It subsequently performed the first inspection of the filters during Unit 2’s refueling outage in 2008, finding their performance excellent. To date, all of the 544 fuel assemblies with Defender Debris Filters in Peach Bottom Unit 2, and the 276 fuel assemblies installed in Peach Bottom Unit 3 are damage free.
By preventing fuel damage, the Defender Debris Filter decreases personnel radiation exposure, increases electric generating capacity, and maximizes use of reactor fuel rods. Exelon estimates the use of the filter will reduce exposure 1 to 10 person-rem and avoid $7.25 million in costs over each plant’s two-year fuel cycle.
• PSEG Nuclear LLC employees at the Salem nuclear power plant were recognized with the 2009 Westinghouse Design Vendor Award for their Mechanical Stress Improvement Program (MSIP) that mitigates cracking of metal welds on reactor vessel nozzles. The MSIP process compresses the outside of a pipe, and subsequently compresses the inside of the pipe, to eliminate tensile stresses that contribute to stress corrosion cracking. PSEG partnered with Westinghouse to implement MSIP and successfully completed the mitigation of all eight Salem Unit 1 reactor vessel nozzles in less than six days in the fall 2008 maintenance outage. It marked the first time MSIP was successfully performed on nuclear plant piping of this size.
Through the successful completion of MSIP at the New Jersey power station, PSEG has developed an innovative solution that has lead to a 10-year inspection cycle on the Salem nozzles. This schedule will reduce worker exposure by 5 to 10 person-rem and reduce costs. The MSIP application at Salem 1 saves $3.6 million when compared to other mitigation techniques.
• Exelon Nuclear employees collaborated with Plastocor Inc. to earn the 2009 Equipment Reliability Process Award for managing condenser tube aging with internal epoxy coating. Main condenser tubes are subject to several modes of degradation over time. The most significant degradation mechanism is microbiologically influenced corrosion (MIC) that can cause pitting and penetrations through tube walls. Replacing main condenser tubes takes 60 to 100 days, costs $50 million to $80 million, and produces up to 70 person-rem exposure for boiling water reactors. The epoxy coating application can arrest MIC and repair leaking tubes, including tubes that were previously plugged due to leakage.
Exelon partnered with Plastocor Inc. to improve the condenser tube application that has been used in fossil plants. The inside of each tube is cleaned and dried. The epoxy is then injected into the tube and applied by a squeegee that is either propelled by air or pulled with a string through the tube. The epoxy coats the entire inner surface of the tube and plugs any holes. The thin coating prevents MIC, has little effect on heat transfer, and initial tests indicate that formerly plugged tubes can be returned to service. Exelon has four nuclear plants that may need to have their main condensers tubes replaced by 2014. A viable alternative is the in-situ epoxy coating of the tubes. Exelon estimates it will save at least $400 million and reduce radiation exposure to workers by a minimum 300 person-rem. Exelon is the first electric utility to apply in-situ epoxy coating to the main condenser tubing at nuclear plants.
• Exelon Nuclear employees earned the 2009 Nuclear Fuel Process Award for their Next Generation Core Design strategy for boiling water reactors. Collaborating with Global Nuclear Fuel (GNF), the team developed a multifaceted approach that improves reactor core designs. The challenges addressed include: minimizing reactivity manipulations by operators, meeting the demand for long fuel cycles with high energy demands, managing increasing uranium prices, and minimizing control rod interference with fuel assemblies.
The next generation core designs provide important benefits. Safety is improved by eliminating at least four reactivity manipulations per two-year fuel. Also, fewer control rods need to be inserted into the fuel, thus minimizing interference with fuel assemblies. And fuel cycle economics are improved through fuel cycle extension techniques that reduce the number of, or uranium concentration of, replacement fuel assemblies.
Fuel cost savings for Exelon BWRs that fully implemented Next Generation Core Designs from 2006 through 2008 was approximately $55 million. Outage time for maintenance has been reduced because fewer new fuel assemblies are loaded into the reactor. There also are back-end fuel cycle savings through a reduction in the amount of used fuel that is generated. The strategy also improves fuel efficiency by placing fuel assemblies entering their third cycle of operation in the outer three rows of fuel assemblies. This has a secondary benefit of extending the use of the reactor pressure vessel and internals by reducing their radiation exposure.
Exelon’s core design strategy is applicable to other boiling water reactors.
• Duke Energy employees at the Catawba nuclear station and AmerenUE employees at the Callaway nuclear plant shared the 2009 Materials and Services Process Award for the use of high-density polyethylene piping for plant service water systems. South Carolina’s Catawba station was the first U.S. nuclear plant to use polyethylene piping for the replacement of a water system. Missouri’s Callaway was the first U.S. plant to use polyethylene piping in a nuclear safety-related application. Unlike carbon steel piping, high-density polyethylene piping is not subject to corrosion, and it eliminates the need for system pipe cleaning that increases costs and decreases system availability. It also is less costly to install and maintain.
In 1998, Duke Energy employees at Catawba replaced six-inch, low-pressure water piping that provides cooling water to the generator hydrogen coolers. Following the replacement of more than 90 percent of the carbon steel piping with polyethylene piping, flow in the system greatly improved. Catawba is planning to replace 4,000 feet of buried, 10-inch carbon steel piping in the safety-related water system. The use of polyethylene piping will cost $12 million less than the alternative molybdenum piping, and it offers the long-term benefits of being non-corrosive and not requiring cleaning. In 2008, AmerenUE employees at Callaway successfully used high density polyethylene piping to replace 1,600 feet of underground piping in the safety related essential water system (EWS). The original carbon steel piping required numerous inspections and costly repairs. Callaway completed the replacement of one-half of the buried EWS piping in just eight days in December 2008. It will replace the other half in 2009.
Both Catawba and Callaway share information and technology with the nuclear industry for the use of polyethylene piping as a safe and cost effective alternative for replacement of service water piping systems. Their findings and achievements can yield benefits to the entire U.S. nuclear industry, including new nuclear plants.
• Dominion Nuclear Connecticut employees at the Millstone power station were honored with the 2008 Westinghouse Combustion Engineering Design Vendor Award for protecting steam generators at a reduced cost through innovations in condensate polishing. The results have been dramatic. Corrosion has been reduced by 80 percent and the number of steam generator inspections has been reduced significantly, lowering worker radiation exposure. Also, chemical use has been reduced by 50 percent and some resin charge changes have gone from a 10-day rotation to nearly two years. The plant has reduced water use by 16 million gallons a year and nitrogen use by 20,000 kilograms annually. The plant is saving $500,000 annually in chemical purchases, $50,000 in equipment use, and 3,000 worker-hours. It also will save $1 million in reduced maintenance during each maintenance shutdown. This innovation can be undertaken by many plants without major capital investment.
• Omaha Power Public District employees at the Fort Calhoun power station earned the 2008 Work Management Process Award for managing major nuclear refurbishments. Having received a license extension from the NRC in 2003, the OPPD team in 85 days refueled the reactor and replaced the steam generators, reactor vessel pressure head, pressurizer, main transformer, low-pressure turbines, main steam piping and hydrogen coolers. They accomplished all of this, plus typical refueling maintenance, tests and inspections, five days ahead of schedule and $35 million under budget with no lost-time accidents. The process included the creation (and resealing) of a 24-foot octagonal opening in the four-feet-thick steel and concrete containment structure that houses the reactor. The success of this undertaking—the industry’s most extensive plant renovation to date—required excellent planning and work management, and outstanding teamwork.
• Exelon Nuclear corporate employees were recognized with the 2008 Equipment Reliability Process Award for developing a system to effectively monitor plant system performance and equipment parameters at all of the company’s reactors. Based on a NASA-developed cluster algorithm to monitor space missions, the team modified the software to track hundreds of plant processes and identify changes in real time. The software alerts operators to anomalies so plant personnel can investigate situations to reduce the possibility of equipment failure. This improves safety and equipment reliability at all of the company’s plants. In just two months, the system saved the company an estimated $550,000 through avoided repairs.
• Exelon Generation Co. and Westinghouse Electric Co. employees also were recognized with a 2008 Nuclear Fuel Process Award for their zinc addition with high boiling duty pressurized water reactors at the Byron and Braidwood stations to reduce stress corrosion cracking over time. Faced with an alloy that was susceptible to stress corrosion cracking from water that circulates through the reactor, the team sought to mitigate the situation. Employing a decision analysis technique called Decision Advisor to provide extensive analysis, the team determined that the addition of zinc would provide significant benefits. Since the addition of zinc was initiated, the potential for stress corrosion cracking has significantly declined. Another important result is that radiation dose rates associated with the primary system have dropped by 56 percent and related worker exposure by 43 percent. The decision to inject zinc into the system showed a net value of $4.4 million per each pressurized water reactor.
• Exelon Nuclear employees at the Limerick power station are recipients a special 2008 Vision & Leadership Award for their Mine Water Augmentation and River Restoration Fund Project. Demonstrating environmental stewardship and their commitment to be a good, long-term neighbor, the program has enabled the company to secure its water needs for the plant and improve regional water management. By using ground water held in mining sites, the company developed a cost-efficient means to offset its consumptive water needs while helping to protect local community water supplies. The River Restoration and Monitoring Fund created by the team helps to clean up acid mine drainage from abandoned coal mines and provides funding for local and statewide water management and water quality improvement programs in Pennsylvania.