Many users are suffering a massive freeze whenever approaching the BoS Bunker, the game will start slowing down progressively, then eventually freeze. In many cases it'll freeze for a short while then continue, but it's bound to freeze again pretty soon. To solve the issue, all you have to do is:
When the game starts slowing down, simply save your game, then load it. It'll take from 10-15 minutes of loading, but the game won't freeze afterwards.
It's really disappointing to see Dead Money hit the PS3 with such a big bug. Hopefully it'll be fixed, but for now, You'll have to do this every time you do approach the bunker.