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6 APRIL 2017 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 56, NO. 4 UP FRONT Automated System Boosts Nuclear Reactor Crack Detection Professor Mohammad R. Jahanshahi reviews results using the system with doctoral student Fu-Chen Chen. Image courtesy of Purdue University. Purdue University (West Lafayette, Indiana) researchers are working on an automated system to detect cracks in the steel compo- nents of nuclear power plants. "Periodic inspection of the components of nuclear power plants is important to avoid accidents and ensure safe operation," says Mohammad R. Jahanshahi, lead researcher and assistant professor. "However, current practices are time consuming, tedious, and subjective because they involve an operator manually locating cracks in metallic surfaces." Some algorithms struggle to detect cracks, the researchers say, because cracks are usually small, have low contrast, and are difficult to distinguish from welds, scratches, and grind marks. The group's crack recogni- tion and quantification (CRAQ) system, how- ever, uses a technique based on texture changes surrounding the cracks. "Cracking is an important factor in aging degradation that may cause leaking and result in hazardous incidents," Jahanshahi says. But manually inspecting each crack can be challenging. As a result, researchers have turned to video analysis and are searching for ways to improve its reliability. The CRAQ method, which has a patent pending, processes multiple video frames at once. "In contrast to other methods that only focus on detecting cracks in one image, we propose a method called Bayesian data fusion that tracks detected cracks in video frames and fuses the information obtained from multiple frames," Jahanshahi says. "Moreover, we can filter out falsely detected cracks." Future research is aimed at developing a more accurate and fully automated system using advanced software. To learn more, visit purdue.edu. Noncorrosive Flow Battery Cuts Upkeep Costs Researchers from the Harvard John A. Paul- son School of Engineering and Applied Sci- ences (SEAS) (Cambridge, Massachusetts) developed a noncorrosive flow battery to store energy in organic molecules dissolved in neutral pH water. Flow batteries store energy in liquid solutions in external tanks, with bigger tanks storing more energy. As such, they are a promising renewable energy solution. However, many of these batteries suffer degraded capacity after charge-discharge cycles, requiring maintenance of the electrolyte. By modifying molecules used in positive and negative electrolytes, the team engi- neered a battery that loses only 1% of its capacity per 1,000 cycles. "Lithium ion batteries don't even survive 1,000 complete charge/discharge cycles," says Michael Aziz, a professor on the team. "Because we were able to dissolve the electrolytes in neutral water, this is a long- lasting battery that you could put in your basement," adds contributing professor Roy Gordon. "If it spilled on the floor, it wouldn't eat the concrete and since the medium is noncorrosive, you can use cheaper materi- als to build the components, like the tanks and pumps." Researchers say the key was figuring out why previous molecules degraded so quickly in neutral solutions. By identifying how the molecule viologen in the negative electrolyte decomposed, they modified its structure for more resilience. They then used ferrocene, known for electrochemical properties, for the positive. By functionaliz- ing both the same way, they turned an insol- uble molecule into a soluble one that could be cycled stably. The neutral pH could lower the cost of the ion-selective membrane that separates the battery's two sides. Many flow batteries use polymers to withstand aggressive chem- istry, but those can account for one-third of the total cost, the team says. For more information, visit otd.harvard. edu. Cement Heals Itself from Cracks When geothermal wells are made using PNNL-developed self-healing cement, cracks and breaks in the well can heal automatically. Image courtesy of PNNL. Chemist Carlos Fernandez and other Pacific Northwest National Laboratory (PNNL) (Rich- land, Washington) researchers are developing cement for geothermal production wells that can heal themselves when cracks occur. Because wells with cracked cement are vulnerable to leakage, reduced strength, and corrosion, PNNL explains that it is important to repair them in a timely fashion. However, the costs of new materials, excavation, instal- lation, and halting power production can be significant. Fernandez discovered that adding syn- thetic polymers to cement could create self- healing properties. These chain-like mole- cules hold substances together, and Fernandez's team learned that by mixing in 5 to 20% of these polymers into cement before it is poured and cured, the cement could repair itself. The researchers say they have proven this cement can repair within days, and they say it has potential to heal within hours. Just as impressive, however, is the cement's projected ability for continuous self- healing, meaning it can repair itself repeatedly and still maintain its rheological and mechan- ical properties. The work is a collaboration between PNNL, Brookhaven National Laboratory (Upton, New York), and the National Energy Technology Laboratory, funded by the U.S. Department of Energy's Geothermal Technol- ogies Office (Washington, DC). For more information, visit pnnl.gov. —Ben DuBose