content: Those were just tourists on an authorized trip. They were exploring undamaged areas of Unit 4. This floor plan shows the layout of units 3 and 4 at ChNPP: https://carlwillis.files.wordpress.com/2011/08/chnpp_phase_ii_map_raw2.jpg. The control room they visited is in the middle, between the reactor building and the steam-turbine building. The radiation there is not too high, and they're wearing masks to avoid inhaling any "hot particles". If you want to see something really crazy, look what I found in the related videos list: https://youtu.be/NkwEfbIBnDU