Sakharov wont talk to me

I just entered Yantar after helping prof. Kruglov get to Yantar. He isn't in Yantar and yet Sakharov does the first line of his dialogue. After that I can't possibly talk to him, only kill him and take his loot.

Hi alcheimers. Kruglov and Sakharov are important characters in Stalkersoup, so you should make sure they both survive or you won't get very far.

If Kruglov didn't make it to Yantar, chances are he got 'stuck' somewhere in the Wild Territory and was unable to follow you. I suggest that you reload an earlier game and watch to see if this happens. If he fails to follow you at any point, make a Quicksave and then Quickload and this will usually get him moving again.

One place where he frequently gets stuck is at the entrance to the underpass with the Burner (fire) anomalies. After he sends you through he is supposed to follow you, but sometimes he remains on the other side. 

If he makes it through the tunnel, he should stop and talk to you again. After that he makes his own way to the Yantar transition. However, if he detects an 'enemy' nearby, he may get distracted before he makes it through, so make sure you clear out any Mercs, zombies or other critters to clear his path.