Infrared Thermography for In-Pile Imaging of Nuclear Fuel Cracking

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Conference Proceeding

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The objective of this paper is to present preliminary thermal and imaging analysis of infrared thermography applied for crack detection in nuclear fuel. Cracking of nuclear fuel has notable implications on the fuel performance. Cracks provide a pathway for faster fission gas release and buildup of pressure inside the fuel rod. Crack induced relocation of fuel results in pellet cladding mechanical interaction. Lastly the fragmentation of the fuel under severe thermal stress leads to loss of fuel ability to maintain coolable geometry. The aforementioned phenomena impact the life time of the fuel. In-pile detection of the solid material cracking will allow for better understanding of the fuel's thermo-mechanical behavior and allow validation and development of fuel performance codes. In this report, we summarize the result of the modeling efforts to identify an optimal configuration for infrared thermography for detecting structural evolution of the fuel such cracking. Similar approaches can be further expanded and consider fuel void formation, relocation and pellet claddinh interaction. In this modeling effort, various heater configurations including source and geometry as well as ambient temperature conditions were considered. For sources of heating: internal heat generation by fission or gamma rays and external surface heating by a laser were considered. For the external heater geometry, the condition of uniform and point source surface heater were analyzed. A free space setup implementing IR camera with lock-in detection capability has been identified as a first step for achieving in-pile implementation. The ability to detect cracks in-pile will open up possibilities for further advancements in fuel performance.

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