I'd like to enable Nuclearcraft's radiation mechanics, but everything related to radiation management requires bioplastic, which has no recipe.

Radiation mechanics are disabled in the pack and consequently the items only related to that are disabled. Removing these extraneous items pares down JEI to relevant items, which helps avoid confusion.

By design, NuclearCraft is used in this pack as a processing machine for turning fissile materials into other ones. The recipes are specifically adjusted for reduced fuel life to result in faster material throughput.

You can customize your own instance by editing the tweaker scripts to prevent items from being removed, but you may not be able to craft the items if other aspects of the mod (machines, items) are also disabled. It may also imbalance the pack, as we have customized almost every recipe for balance and progression gating.