Re: You join an expedition to retrieve data tapes deep within the Chernobyl catacombs
Nuclear power plants (with no power) are like concrete caves. Chernobyl inside the sarcophagus is more so a dark pit. One thing I noticed is that there are a lot of holes to fall in. That was my main worry last time I was in a similar building: We actually called the place "Super Death Plummet." Several types of machine and tankage are multifloor affairs, and once damaged they leave unguarded holes in the floor. My main concern would be having enough floody lighting to see my surroundings, enough runtime to make it in and out, and a more-throwy light to see distant 'landmarks.' Line of sight is usually short in nuclear plants, though. You'd want maps, whatever photos and notes from the fire event, protective equipment, and a death wish.
Edit: Oh, and headlamps are nice. Very nice. After all, those data tapes aren't going to carry themselves!