Power nuclear train by FBR.

When having a FBR, the current recipes do not allow to construct nuclear rods for the nuclear train. Some solutions:
- Uranium (20%) -> Uranium rod recipe
- Enriched blanket fuel -> Uranium (4%) recipe
- Nuclear train accepting MOX rods
- Nuclear train accepting core fuel

It is in fact more efficient to make nuclear rods and burn them in Nuclear plant I or II and then reprocess it for FBR than direct yellow cake to blanked fuel (although more complicated). There could certainly be U20 to U4 recipe, but nuclear trains requiring only nuclear rods and not MOX/core makes sense, as it needs as simple reactor as possible.