In the next update, when the distilled water reactor is introduced, fuel rods will deplete based on their neutron output, but only for distilled water reactors.
In the update after that, that will be reverted and reactors, but at and after a certain fuel specific neutron output per tick, fuels will lose durability four times as fast and scaling with output. The reason this is done is to make fuel efficiency (i.e. total energy output per fuel rod) simpler to understand. Higher output equals higher efficiency up to a certain fuel specific point, where it suddenly becomes less efficient.
This update will also introduce a new mechanic of fuel breeding similar to IC2, so you can get U233 and Pu239 from breeder rods of Th232 and U238.
I may also do better byproduct recipes for the depleted fuel rod, but I’ll have to do a bit of research first.