I played the scene over a dozen times last night, which trumps your three viewings, and I'm still convinced that he doesn't say "aft nacelle".
There is nothing within the Star Trek lexicon that remotely sounds like aft nacelle...
Certainly not in the pre-JJverse Star Trek Lexicon. However within the JJverse itself, that may no longer be the case.
Also... in response to an earlier post:
"Located behind the ar-se-nal"?
A place where weapons and military equipment are stored or made.
That's the way the syllables of the word actually fall. Nothing laughable about it. Nor is it at all unthinkable that Khan would draw attention to every syllable, to drive home the point that he knew precisely where to hit them.