Nuclear Executive Update   
An EPRI Progress Report, September 2010
INNOVATION CORNER
Roadmap Defines Sensor Technology Challenges and Opportunities

New reports describe current needs and future opportunities for nuclear-grade sensors and outline plans for advancing measurement and on-line monitoring technologies for existing and advanced reactors.

Nuclear power plants typically incorporate hundreds of sensors that are subject to environmental, safety, seismic qualification, and performance verification requirements. EPRI’s Office of Technology Innovation is conducting strategic research to address the new demands being placed on existing nuclear-grade sensors as well as the sensor-related challenges and opportunities facing current and advanced plants.

Nuclear-grade sensors must provide accurate and timely data to reactor control and protection systems during normal operations and post-accident conditions. The technologies underlying today’s temperature, pressure, fluid level, and fluid flow transmitters and neutron detectors have not changed much in the past 50 years, but existing sensors are being required to perform new functions. In addition, novel sensor designs and concepts are emerging, and on-line monitoring is increasingly being applied for sensor calibration and validation and for condition assessment of key components.

A recent report, EPRI Nuclear Sensor Roadmap (1020956), describes sensor-related issues, needs, and technologies relating to aging and obsolescence, instrumentation and control (I&C) retrofits, power uprates, long-term operations, and new builds. A key conclusion is that the relatively small market for nuclear-grade sensors leaves the industry vulnerable to near-term supply shortages and may lead to under-investment in emerging technologies, many of which offer potential to meet the changing needs of existing plants and the challenges posed by advanced reactor designs.

According to the report, advanced feedwater flow and temperature instrumentation allows existing plants to operate closer to performance margins and produce additional power without compromising safety. Smart pressure sensors are entering commercial service, while wireless vibration, temperature, and humidity sensors show great promise for improved situational awareness and predictive maintenance by providing insight into operating conditions and the status of rotating machinery and other components. Radiation-hardened fiber-optic sensors are expected to contribute in the areas of temperature and strain monitoring, and they represent a leading platform for high-temperature gas reactors that will operate at coolant temperatures three or more times higher than those of light water reactors. These and other advances will expand the applicability of on-line monitoring for real-time process optimization, condition assessment, and sensor calibration and trending, highlighting the need to address data acquisition, storage, processing, and display capabilities during the design of I&C system upgrades and new plants.

The report concludes with a review of near- and long-term R&D priorities and application issues to be addressed by industry stakeholders in order to advance the state of the art in sensor technology for nuclear power plants. Two complementary reports (1020394, 1020496) provide detailed information on R&D needs specific to distributed fiber-optic Bragg grating sensors. By allowing measurements to be taken along the length of the fiber, rather than just at the fiber tip, these sensors could enable three-dimensional reactor temperature mapping, monitoring of flow-accelerated corrosion, evaluation of pressure vessel integrity, and other high-value uses. Ongoing strategic research at Penn State University is exploring corrosion monitoring applications for process piping; a longer-term development challenge involves mitigating the effects of radiation exposure on light transmission and of temperature embrittlement on survivability.

For more information, contact Rick Rusaw, 704.595.2690, rrusaw@epri.com.


Fiber Bragg grating-based sensor