Cost Saving When Using Enhanced Conductivity Nuclear Fuel Containing BeO in WWER-1000 Reactors

Current pressurized water reactors utilize sintered UO2 that has a number of advantages and disadvantages. Uranium Dioxide’s low thermal conductivity results in a large thermal gradient within the fuel pellet corresponding to higher centerline temperatures compared to other potential fuel forms. These gradients result in non-uniform thermal expansion leading to large internal stresses resulting in cracking of the pellet and fuel-clad interaction, which can lead to loss of the integrity of the fuel pin. Higher fuel temperatures also increase the release of fission gases. Fuels with higher thermal conductivity may alleviate or reduce the severity of these adverse conditions. It is shown that higher thermal conductivity can be obtained by adding BeO to the basic UO2 matrix. This paper focuses on WWER1000 hexagonal fuel geometry. Improvements when using 10% of BeO, as proposed in this paper, reduce the centerline nuclear fuel temperature by 234°C and improve the fuel economy while reducing its cost by 7%. The study was done for NPP Temelín which has two units WWER1000/320.