Depending on the code on your code of record and the requirements of this slab what you are proposing may or may not be acceptable. For example, if the slab needs to meet ACI 318-19 and it is part of your seismic force resisting system (Cat C through F) you would have to repair the cut rebar...
I am not sure if the NRC provides a generic template. The steps for licensing of a nuclear power plant are outlined per 10 CFR Part 50:
https://www.nrc.gov/reading-rm/doc-collections/cfr/part050/full-text.html
You can also google a NRC approved design as an example ("AP1000 DCD").
Can the...
The code of record depends on the class of safety/seismic category of the structure you want to design.
Typically, the critical structural elements in containment are governed by AISC N690 (steel design) & ACI 349 (Reinforced Concrete design). Piping design codes typically falls under ASME...