QUANTITATIVE BORESCOPE INSPECTION OF NUCLEAR REACTOR COMPONENTS INCORPORATING LOW COHERENCE INTERFEROMETRY

Regular inspection of piping for corrosion damage is crucial in nuclear power plants to prevent leakage of radioactive material into the environment, and to allay concerns of residents living within the vicinity. However, currently used methods for detecting corrosion on interior surfaces of reactor components are difficult to apply in confined spaces and do not always provide enough information. A critical need exists for a compact sensor for inspecting surfaces more completely, especially inside small pipes and other hard to reach places in a nuclear power plant. An optical method is proposed for detecting and characterizing corrosion in components of a nuclear reactor using a compact sensor head that is fiber optically coupled to a detection system. The technique is low coherence interferometry, which enables three-dimensional surface profiling of the ID of a pipe with micrometer precision, and also provides diagnostic information about the oxide layer and corrosion that typically occurs inside the pipe. Because of its compact size and ability to operate remotely, coupled with the ability to rapidly profile and characterize corroded surfaces, the proposed sensor would enable inspections of critical difficult-to-access components of nuclear power plants, such as the drain line at the bottom of a boiling water reactors pressure vessel. This capability would increase the level of confidence in the safety of nuclear power plants as well as in a wide range of other facilities where inspection plays an important role in safety.