AFA 3G Operating Experience

The AFA technology was developed in the 80’s and since then has been continuously improved by Framatome to provide utilities with high performing products for more demanding plant operating conditions. Thermal hydraulic performance enhancements and transition to new materials for cladding, guide tubes and grids accomplished through the AFA 2G and 3G generations, accompanied the utility needs. The burn-up increase and the achievement of more demanding conditions was supported by the development of the M5Framatome alloy which allows the AFA 3G fuel assembly to achieve a licensed Fuel Assembly (FA) burn-up of 62 GWd/t. M5Framatome alloy brings to the fuel assembly a high resistance against corrosion and hydriding allowing burn-up increase. Moreover, the use of M5Framatome alloy provides the AFA 3G fuel assembly with a higher maneuverability allowing Extended Low Power Operating conditions and allows that LOCA margins would not be hindered by the presence of highly irradiated fuel assemblies for high burn-ups. The AFA 3G grid design results from improvements of the original AFA design and enables the AFA 3G fuel assemblies to support optimized fuel management and plant power up-rates. The fuel assembly performance can be further enhanced by addition of MSMGs (Mid Span Mixing Grids). The AFA 3G grid has also been optimized to facilitate the reshuffling of the cores. The evolution of the fuel managements mainly characterized by increased burn-ups and increased resident times required further improvement of the fuel assembly design with regards to the increased risk of Grid to Rod Fretting and Fuel Assembly bow in particular for 14 ft—4 loop plants. The AFA 3G 14ft design has been reinforced by the implementation of new structural material, the Framatome Q12 zirconium alloy, featuring enhanced creep resistance to preclude the risks of Fuel Assembly bow. This was done in a two-step approach with the implementation of Q12 MONOBLOC guide tubes followed more recently by the implementation of Q12 AFA 3G grids. The current AFA 3G fuel assembly design is the result of the integration of an extensive Operating Experience acquired by Framatome in many different types of reactors and more particularly in the 12ft and 14ft 17x17 plants. Framatome delivered more than 43000 AFA 3G 17x17 fuel assemblies providing an outstanding Operating Experience that will be highlighted in the paper.