Not sure I'm fully understanding but I'll take a crack at it....
1) App. 7-4(b) states if you are performing a repair it can not be deeper than 5% of the INTENDED thickness at the location of the defect. Otherwise welding will be required.
2) App. 7-4(c) will lead you back to 7-3, more...
There are quite a few variables determining how much and what level of ndt to use. I might be misunderstanding but an xray of a nozzle to shell joint (cat. D) would be not impossible but impractical and ultrasound would be more fitting due to the geometry of the joint. A weld neck flange (cat. C...