In my opinion the welding inspector is correct in that UT of the corners is difficult. However, and also in my opinion, he is dead wrong if he believes that fact in and of itself means that you don't have to UT the corners. That is the Engineer's decision and has absolutely nothing to do with the opinions of any welding inspector.
Think about it from this point of view - the Engineer believes that these welds are important enough that they are specified to be CJP and they are required to be UT'd. The corners are the most difficult portions of these joints to weld (this can be surmised by additional welder qualification test requiring a macroetch that is required for box tubulars). Why would the Engineer simply say that it is okay to not inspect the most difficult portion of the joint to weld, simply because it is difficult to inspect.
Anyway, this is the Engineer's decision.
Mankenberg
I've performed this in the past, but your not going to do it with the standard AWS setup. Your weld inspector is stepping out of his or her bounds stating so in the manner you quote. The only really difficulty I see is that the engineer needs to be more specific with requirments and will likely need a D1.1 experienced LIII UT hand to design the test around the given acceptance criteria.
can it be done? Yes
Is it easy? no
Regards,
Gerald
CWI
LIII UT, MT, PT, VT, RT