When you visit a C6 RB, you see a lot of empty space between the SG’s, above the reactor deck.....
It seems to me that it would have been relatively easy to position a spare calandria (or two) inside, before the dome is closed up.
Having decided against doing that, the building should have been made so as to allow calandria replacement.
Not having done either leaves us with few options :<( ....one of them being decommissioning w/o retubing, as at Pickering A.
In cdn-nucl-l digest, Vol 1 #2664 it was reported that the Bruce retube manager suggested at the recent CNS Conference in Calgary that it could be less costly to cut a large whole in the containment building and replace the entire reactor assembly as a module, instead of re tubing it.
Comments by Neil Craik;
1. This is not possible on the CANDU6s because the containment building prestressed cables are pressure grouted and cannot be removed/replaced. On some US containment buildings the prestressed cables are pressure oiled and so can be removed/placed. This may have been done on some US plants to replace the Steam Generators During the construction of at least one C6, the pressure grout seeped through cracks in the ring beam ensuring a solid structure. Pressure oil would worsen such cracking and also needs a steel liner.
2. The dousing system and support structure would have to be removed/replaced; a huge task.
3. I know that C6 calandria’s had CT’s installed before the calandria was moved in horizontally into the reactor building (RB), but I am not sure if the PTs were also installed outside of the RB. I can recall discussions about whether this would put a strain on the PT joints.