^ Thank you, Ikalugin
So if i understand this right (much simplified):
The big mechanism (gantry crane) in the background is for extracting/exchanging the fuel rods.
Control rods consist of two sets, one bigger and longer set can be extracted/inserted from the upper side, the other smaller and shorter set from the lower side (control rods are different depending on task)
As you said the mechanisms/engines to move the control rods must be somewhere in or near the area of the upper and lower biological shield.
There are two fuel rods stacked above each other in each one pressure pipe.
So the pairs are connected/linked to each other so they can be axtracted together from above with the ganty crane?
The mechanism/engines for inserting extracting the fuel rods are in the area of the control rod engines? If the pairs are connected then the engines for fuel rod control should only be in the upper part?
