I'm not familiar with foundry NDE requirements but I would think that there should be procedures to follow in the companies Quality Manual.
That being said, I would suggest MT in addition to UT if it is a ferromagnetic material.
There may be a defect or discontinuity just below the surface that might not be detected by UT. Just happened to us on a Produced Crude pipe. UT didn't catch it because it was so close to the surface but when we applied heat to the pipe OD, large blisters developed, causing us to stop work and re-evaluate the situation.
I'll try to post pics when I am on another computer. A pretty odd situation.
You wouldn't happen to be working Southern Peru Copper would you? ASARCO had standards and procedures in place before they were sold to Grupo Mexico. Grupo also has those procedures in place as well. I ask because that pot design looks extremely familiar to me, in particular the trunnion area. I've seen a lot of those pots in various parts of the world, and those were unique in my experience.
Assuming the above, I strongly advise you not to reinvent that particular wheel if you don't have to. However, if you must, be sure to apply straight beam UT exams down the trunnion axis with an eye towards hot cracking, and florescent MT on, and around the trunnion areas. Those are the weakest points in that design. In any case, I would also strongly suggest getting a third party involved if they will let you. Last time I was in Peru, RTDApplus was still alive and active, as well as SGS. One of those two will very likely have personnel that have performed those exams already.
My two cents worth on that.