Horizontal Control Rods - Inner Room

This view of the lower level of the inner room shows the two lower racks of horizontal control rods. Also visible is the entrance to a labyrinth that leads to the outer room.

The labyrinths that connected the inner and outer rooms blocked radiation while allowing access to the inner room. Safe entry to the inner room could only be made either when the rods were either fully inserted into the pile or after the pile had been shut down and the rods had cooled off for about a week.