Infrared Thermography Method to Detect Cracking of Nuclear Fuels in Real-Time

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The efficiency and performance of nuclear fuels are essential to the safety, reliability, and economics of nuclear energy. Crack formation occurs relatively early in the fuel operation cycle and lowers its life and efficiency; accordingly, understanding crack formation and propagation in fuels is key to evaluating and improving fuel performance. The harsh environment inside a nuclear reactor is the primary challenge for real-time fuel monitoring. A coherent fiber optic bundle (CFOB) based infrared thermography (IRT) method may be a viable method for real-time fuel monitoring. A radiation hardened, temperature resistant CFOB can be used to transmit a real-time image from inside the harsh reactor environment to the near infrared (NIR) camera outside the reactor. In this paper, the feasibility of the method was tested and confirmed on oxide nuclear fuel surrogates in a laboratory setting. Two different fuel surrogate materials are showcased with and without the CFOB using furnace heating, laser heating, and reflected illumination from an incandescent bulb. The behavior of common features, such as cracks, mounds and pits, were all compared in detail for the different heating/illumination techniques and samples for temperatures ranging from 23–500 °C. The effects of five different image processing techniques were also studied. Cracks down to ≈ 300 nm wide with a field of view of ≈ 6.4 × 5.12 nm were easily detected with the IRT system with and without the CFOB.