I think you are past this point, but you may not have seen this task as you have to return to Fanatic (at the camp fire in Cordon) several times.
Fanatic can teleport MO to three locations when he has the necessary data. The third location is to the Sarcophagus, and for this Fanatic needs info from a computer in the bus station in Pripyat. The dialogue (in sak_strings.xml) is:
MO: "Hey, right in the Sarcophagus can be reached?"
Fanatic: "Probably can only data out there, and I do not know where to get...
And this is where the geological survey of Pripyat is - I know..."
MO: "Ha! Certainly in most Pripyat..."
Fanatic: "Exactly! You'll be there, look in the building of the bus station, computer data such as should have been preserved..."
MO: (either:) "Okay, still in the wrong direction, look!"
(or:) "If get to Pripyat, things to do will..."
I think MO's options are a bit confusing as to which answer accepts the task. (The first option gives the task.)