Fabrication of uranium oxide fuel pellets using the IDR powder process

The British Nuclear Fuels Limited (BNFL) IDR powder route is now well established and several papers have been published describing this short one-stage process, which has been operated at BNFL's Springfields Works, United Kingdom, for over ten years and has been licensed to other major fuel manufacturers. The IDR technique consists, in brief, of feeding UF6 vapour with steam through a jet to form a plume of UO2F2 powder which is then ejected into a rotating kiln where it meets a counter-current flow of hydrogen and steam. The product UO2 of high reactivity and fine particle size is discharged from the end of the kiln through check-hoppers into product containers. IDR powder has been used for both AGR and LWR fuel programmes. To date over 3000 t uranium of fuel has been fabricated using this powder. The consistent quality of the powder has been shown by its use for binder and binderless pelleting routes using both multi-punch hydraulic presses and multi-station rotary presses, and the versatility of the powder has been demonstrated by its ability to be used with additives for pellet density control, burnable poison fuel, and pellet grain refinement. The extensive use of IDR powder to make LWR fuel has enabled much irradiation proving to be logged, supported by post-irradiation examination. This has shown fuel performance in line with predictions. Over half a million fuel rods are under irradiation and several batches have completed full life burnup before discharge. (author)