NSUF 20-4134: Effects of Energy Deposition Resulting in Radiation Induced Defects on the Thermal Conductivity of UO2 Fuel Pellets with Negligible Burnup

Fission events occurring in UO2 fuel during the operation of nuclear power plants result in deposition of fission energy within the fuel pellets. Consequently, radiation induced defects are formed affecting the thermal properties of the UO2 fuel. The thermal conductivity of the fuel pellets is diminished giving rise to elevated fuel operating temperatures and large, few hundred degrees Celsius, temperature gradients within a single UO2 pellet. Thermal stresses caused by these large thermal gradients, in addition to the presence of fission and decay products retained within the fuel, eventually lead to pellet swelling initiating undesired pellet-cladding interactions (PCI). Although, using UO2 fuel from a commercial power plant, it is possible to gain insight on the overall effect of having both radiation induced defects as well as high burn up on the thermal conductivity of the fuel, this approach will not be sufficient in evaluating the significance of each of the two contributors. Therefore, examining the extent and mechanism by which defects induced by fission energy deposition in the fuel affect its thermal conductivity without interference from fission products, provides a step forward in developing a thorough understanding of heat transfer in nuclear fuel under real reactor conditions. Hence, the thermal conductivity on two TREAT specimens that have almost no burnup will be studied and compared to a pristine UO2 sample. In addition, via complementary transmission electron microscopy (TEM) analysis of these specimens, insights about the influence of defect formation due to fission energy deposition on their thermal conductivity will be derived.

추가 정보

필드	값
Abstract	Fission events occurring in UO2 fuel during the operation of nuclear power plants result in deposition of fission energy within the fuel pellets. Consequently, radiation induced defects are formed affecting the thermal properties of the UO2 fuel. The thermal conductivity of the fuel pellets is diminished giving rise to elevated fuel operating temperatures and large, few hundred degrees Celsius, temperature gradients within a single UO2 pellet. Thermal stresses caused by these large thermal gradients, in addition to the presence of fission and decay products retained within the fuel, eventually lead to pellet swelling initiating undesired pellet-cladding interactions (PCI). Although, using UO2 fuel from a commercial power plant, it is possible to gain insight on the overall effect of having both radiation induced defects as well as high burn up on the thermal conductivity of the fuel, this approach will not be sufficient in evaluating the significance of each of the two contributors. Therefore, examining the extent and mechanism by which defects induced by fission energy deposition in the fuel affect its thermal conductivity without interference from fission products, provides a step forward in developing a thorough understanding of heat transfer in nuclear fuel under real reactor conditions. Hence, the thermal conductivity on two TREAT specimens that have almost no burnup will be studied and compared to a pristine UO2 sample. In addition, via complementary transmission electron microscopy (TEM) analysis of these specimens, insights about the influence of defect formation due to fission energy deposition on their thermal conductivity will be derived.
Award Announced Date	2020-07-14T14:09:06.44
Awarded Institution	None
Facility	None
Facility Tech Lead	Alina Zackrone
Irradiation Facility	None
PI	Tro Babikian
PI Email	[email protected]
Project Type	RTE
RTE Number	4134