We were playing this last night and the resident rules lawyer questioned the ability to use Nuclear Power to advance tech if it was not in the 5th slot, arguing that the wording on the card 'if in 5th slot' Then advance tech precludes the right to use the card in any slot but the 5th.

It seemed to me that one could use the tech advance in any slot.

Thanks in advance for clarifying.

I'd say your lawyer is wrong. The card has two steps: first, a condition that you may meet or not (if in the 5th slot, then X happens). Then , whether that step and its requirements were met or not, advance your tech dial a number of spaces equal to this slot's number.

If you could only use the card in the last slot, it wouldn't say "equal to this slot's number", it would simply say 5 spaces. Also I'm sure the card would be more specific as in "use only on the 5th slot".