{"id":27461,"date":"2020-07-09T08:10:32","date_gmt":"2020-07-09T08:10:32","guid":{"rendered":"http:\/\/sitepourvtc.com\/?page_id=27461"},"modified":"2023-08-02T06:21:17","modified_gmt":"2023-08-02T06:21:17","slug":"uranium-dioxide-uo2","status":"publish","type":"page","link":"https:\/\/sitepourvtc.com\/nuclear-power-plant\/nuclear-fuel\/fuel-assembly\/fuel-pellets\/uranium-dioxide-uo2\/","title":{"rendered":"Uranium Dioxide – UO2"},"content":{"rendered":"
Uranium dioxide is a ceramic refractory uranium compound, in many cases, used as a nuclear fuel. Most LWRs<\/a> use uranium fuel<\/strong>\u00a0in the form of uranium dioxide (chemically UO<\/strong>2<\/sub><\/strong>)<\/strong>. Uranium dioxide is a black semiconducting solid with very low thermal conductivity. On the other hand, uranium dioxide has a very high melting point and has well-known behavior.<\/p>\n Uranium dioxide has a significantly lower density than uranium in metal form. Uranium dioxide has a density of 10.97 g\/cm<\/strong>3<\/sup><\/strong>, but this value may vary with fuel burnup because, at low burnup, densification of pellets can occur, and at higher burnup, swelling occurs.<\/p>\n See also:\u00a0Thermal Conduction of Uranium Dioxide<\/a><\/p>\n The\u00a0thermal conductivity\u00a0<\/strong>of\u00a0uranium dioxide<\/strong> is very low when compared with metal uranium, uranium nitride, uranium carbide, and zirconium cladding material. Thermal conductivity is one of the parameters determining the fuel centerline temperature<\/strong>. This low thermal conductivity can result in localized overheating in the fuel centerline; therefore, this overheating must be avoided. Overheating of the fuel is prevented by maintaining the steady state peak linear heat rate<\/strong>\u00a0(LHR) or the\u00a0Heat Flux Hot Channel Factor \u2013 FQ<\/sub>(z)<\/a> below the level at which fuel centerline melting occurs. Expansion of the fuel pellet upon centerline melting may cause the pellet to stress the cladding to the point of failure.<\/p>\n Thermal conductivity<\/strong>\u00a0of solid UO2<\/sub> with a density of 95% is estimated by the following correlation [Klimenko; Zorin]:<\/p>\nThermal Conductivity of Uranium Dioxide<\/h2>\n