Advanced Laser Ultrasonic Sensor for Fuel Rod Characterization

Advanced sensors and instrumentation are required to extend the life of current nuclear power reactors, and for use in next generation reactors. Sensors must operate effectively in the harsh reactor environment. Current fuel-rod sensors may be limited by low reliability or slow test procedures, may require disassembly of the fuel rod array, and/or are unable to measure pressure increase above nominal. Laser ultrasonic technology has demonstrated the capability to measure changes in internal pressure in a nuclear fuel rod, which can indicate gas leakage or buildup from fission gas generation, and in wall thickness of the cladding, which may indicate corrosion or oxide buildup. A small laser ultrasonic probe will be designed to make noncontact measurements of a fuel rod within a rod array assembly. In Phases I/II, the feasibility of applying laser ultrasonic testing for noncontact measurements of nuclear fuel rods was demonstrated in air and under water, such as in a spent fuel cooling pool. Novel signal- processing algorithms were developed for high measurement sensitivity and accuracy. A specialized testing station was designed and constructed to enable more thorough testing under a wider range of operating conditions. Novel probe designs for inspection of all fuel rods within an array without disassembly are being developed and tested. In Phase IIB the contractor is requesting additional financial support for new tasks and activities that extend beyond the scope of the Phase II project. The proposed work will develop new data-processing algorithms and software, establish new measurement methods that ensure high accuracy in the lab, redesign the miniaturized testing probe, test the prototype heat and radiation resistance, test the probe in a research cooling pool, integrate the probe design, and design a turnkey test system. End users of the developed laser ultrasonic sensors and instrumentation will be nuclear power utilities and laboratories developing test reactors. Beyond monitoring fuel rods, the sensor is also expected to find application in monitoring other reactor components such as the containment vessel and cooling components. The range of applications also extends to the new class of molten salt or liquid metal-cooled microreactors. Dual-use commercial markets include conventional coal-fired and gas-fired power utilities. This project will contribute to extending the operating life of current nuclear power plants and more efficient functioning of the next generation of plants; commercial plant operators and manufacturers of plant components, particularly fuel rods, will benefit. The public will benefit from reduced power costs and from safer, more reliable, and sustaining power generation. Summary for Members of Congress: This project will give nuclear researchers a valuable diagnostic capability that will eventually be implemented in existing and new nuclear power plants. The proposed laser-based ultrasonic measurement instrument will improve monitoring of the health of active fuel rods, improving reactor safety and reducing the cost of nuclear power.