Local Announcement:“Chief of Project E, Dr. Ritsuko Akagi of the Bureau of Technology's First Division. Dr. Ritsuko Akagi.”
Keisuke-kun: Where is she? Doesn't look like the Cage.
MDWigs: And why is Ritsuko swimming around in it?
Reichu: It doesn't look like any place we see elsewhere in the anime. If it means anything, Shinji and the others go past this location during the hovercraft ride in the manga.
TheAtomicWaffle: I always assumed that this was some sort of work-engine for the coolant that the Evas reside in, seeing as how this large machine is very much swimming in it. Maybe Ritsuko was preparing it to work later, for when they needed the coolant to be drained. Given her closeness to Gendo, she probably knew that they were definitely going to launch EVA-01.
Reichu: If your idea about these pipes is correct, why put Ritsuko in charge? There are plenty of grunts in scuba gear (see C-233) to do this kind of menial work.
TheAtomicWaffle: Probably just a way for the writers to introduce the character, perhaps?