When reaction technicians move radiation shields on casters, they maneuver them so easily that it's obvious the shields aren't made of real lead.
After Dr. Marshall finishes assembling the fusion bomb, he leaves it in the fissionable materials vault and locks the door. He is still inside at the time, and there is no other way for him to leave the vault.
The console below in the control room (below the window viewing the reactor room) is an audio control console. The meters seen on it are VU meters. This console would have nothing to do with radioactivity or experiments dealing with it.
At about the 19 minute mark, when Griffin bounds into the room to tell Dr. Marshall of the impending doom, the set floor flexes so much that the "equipment" stacked behind and to the side of Dr. Marshall sways back and forth very noticeably.
When Arndis Pollard rushes into the reactor room to rescue her husband moving flashes of light can be seen playing over the walls and furniture. Then when Griffin follows her into the room, the camera pulls back to briefly reveal a rotating "disco ball" at the edge of the frame, the reflections off which are the source of flickering lights.