I'm curious. The tour guide guy—since he's regularly giving tours of these areas, would he be exposed to enough radiation for it to have an effect on him?
I guess you'd want to monitor the levels and periods of exposure pretty closely. There are still people working at Chernobyl (containment, monitoring)... In fact, the plant kept operating for over a decade after the incident.
Not sure this is standard practice -- but there are also drugs you can take to lessen the impact.
Watching it now. At about the 36-minute mark a bunch of technicians dig a tunnel into the base of the reactor 15 days after the incident. The footage is terrifying.