This paper will report on the development of this novel LUT instrument based on a unique patented fiber-optic detector that is especially well adapted for field use. The detector design consists of merged Sagnac and Polarimetric interferometers. It is built with polarization-maintaining optical fiber and fiber-connectorized components. Key features such as auto-focus and a fiber-optic integrated generation and detection probe make this LUT system efficient and easy to use. The LUT probe is compact and uses a flexible link (electric cables and optical fibers) to connect to the main unit. It also dynamically adapts its position to the inspected surface in order to detect ultrasound waves. This new LUT capability is has been demonstarted in fossil power plant environemnt and is now ready for application in nuclear power plant environment.

The LUT system has been tested on a section of a hot welded pipe section from a nuclear power plant. We were successful in demonstrating the ability to accurately measure thickness and the capability to detect flow assisted corrosion under the weld crown. Numerous applications in power plants could benefit from this technology, in particular the inspection of hot components for thermal fatigue damage and corrosion.