July-August 2018 NPJ

50 NuclearPlantJournal.com Nuclear Plant Journal, July-August 2018 I&C System... ( Continued from page 49) and corrosive coolants expected in the primary systems of advanced reactors. For example, at high temperatures (i.e. above 500°C), RTDs become susceptible to metal ion contamination of the platinum wire sensing element which affects its purity and ultimately the electrical characteristics of the RTD. This effect is irreversible and results in calibration drift. This is a liability because frequent sensor maintenance or replacement to combat increased calibration drift or premature response time degradation is not practical for advanced reactors with extended operating cycles. Therefore, new I&C sensors must be developed and qualified for service in these unique operating environments. These sensors must also be in-situ testable as installed in the plant for calibration and response time. Currently, researchers at national and international laboratories, universi- ties, and commercial organizations are working to develop I&C sensors for next generation nuclear reactors. These sen- sor technologies include Johnson Noise Thermometry, Fiber Optics (for tempera- ture and pressure), and ultrasonics (for temperature and flow). Table 3 provides a list of some of these emerging sensor technologies. Although many of these concepts are promising, it is important for sensor developers to understand themany aspects of sensor performance in an operating plant as well as the nuclear qualification Table 3.- Examples of Emerging Sensors for Next Generation Reactors process to supply robust products to the industry and support the deployment of advanced reactors. Also, it is important to involve sensor manufacturers early to ensure that a viable supply chain will exist to support the next generation of reactors for years to come. Today, there is less than a handful of reliable suppliers of nuclear qualified sensors for the nearly 450 nuclear power plants operating around the world. It is anticipated that less than a dozen advanced reactors will enter operation in the next two decades. Therefore, the small market for process sensors for new reactors is not a very big incentive for manufactures to invest to design, develop and qualify new sensors for advanced reactors. Ongoing Research As a part of a research and development (R&D) project funded by