@district
I'm thinking of using it as a setting a future book as I guess it's the kind of place most people haven't seen inside. Have to be careful what I say though for obvious reasons!
Most of the buildings are big warehouses in design. The thing I probably found most fascinating as a newbie was the changing room where you go from clean to dirty. It looks a bit like a swimming pool changing room, divided in half by a sort of ridge/bench that crosses the entire room and marks the separation of contaminated zone and clean zone. You change out of your clothes and put, as an absolute minimum, a boiler suit on (whatever your seniority). You have knee length regulation socks which you tuck the trousers into, so the socks can be seen up to your knees. Then, IIRC, you swing your legs over the barrier and straight into what are almost certainly bowling shoes, without touching the ground. You then add various types of protective clothing, depending on how contaminated the zone. From gloves and white suits through to gas masks and almost astronaut type suits.
You also wear personal dosimeter at all times, which measures your annual radiation dose, this is recorded by HR, because if you exceed your annual dose you have to leave the zone for months. In heavily contaminated buildings you also have a sort of personal geiger counter clipped to your boiler suit, which crackles all the time.
You cannot eat, drink, apply lipstick or, most bizarrely, take snuff (there are signs up everywhere warning against using snuff!), basically anything that passes your lips/nose is a risk. You also have to cover any even small open wounds with dressings. If you want even a sip of water you have to leave the dirty zone, decontaminate etc, which takes bloody ages.
Most of the buildings have lots of metal walkways, very 1960s looking computer equipment, all cream ceramics. The fuel ponds where they keep the rods cool are like deep swimming pools. The air is weirdly pressurised, to keep the contamination in, I think.
I've worked in a different nuclear site where the reactor was the size of a an average sized sitting room, and there was a gangway going up and around. It was like a giant box sitting in the middle of a warehouse.
To get clean you have to take off all your clothes (boiler suit etc), wash, swap sides - you sit on the bench things and swing your legs over to the clean side. Then redress. Then a number of different radiation scans and checks including a weird automatic gate a bit like a 3D scanner at the airport, where you press your hands on one plate and lean your arse on the other plate. Then to leave the building itself you use a hand held scanner before you can go, even the bottom of your feet get checked.
I've also lived in a Grade I * tourist site. Nothing like a crowd of tourists outside your window taking photos of you and your family eating breakfast.