The main problem here is that everyone wants to kill you. The Monolith defending the approaches to the station. Military stalkers storming the nuclear power plant from several sides. Mi-24 helicopters liberally spraying bullets and missiles. And even an infantry fighting vehicle, which will harass the player with its machine gun at the entrance.
The goal here is to enter the building near Reactor Unit 4. Prepare your sniper rifle and turn left following the pipe. When helicopters fly overhead and fire at the entrance (you can hear radio chatter from soldiers, snipers, and pilots), pick off a few Monolith stalkers in front of the gate and dive inside as quickly as possible. If you linger near the brick substation building, you'll attract the attention of helicopters, infantry fighting vehicles, and military stalkers armed with silent assault rifles.
You can climb into the trailer to catch your breath, but it's not a good idea to linger there. Run across the road and carefully move along the long building, hiding behind concrete structures, pipes, and rebar. The niches in the concrete blocks are your best friend; you can hide in them if things get too hot. The helicopters and military stalkers will distract the Monolith, but you'll get some. Look carefully to see if there is a stalker running ahead with a machine gun - a gray uniform on gray concrete is very difficult to see.
When the military stalkers enter the courtyard, the harbingers of the impending release will appear. This means you only have five minutes to get inside the building before the release kills you. It's not much time, but it's enough to take your time.
Note: the release only affects the main character and only if they're near the ground. This means you can run freely along the rooftops during the release, which we'll get to shortly.