API 1104 is silent with respect to welder qualification (See Sections 6 and 12.6). Although it may provide guidance for destructive and non-destructive testing, the prevailing code will determine if qualification via radiography is acceptable.
For example, qualification via radiography alone for compliance to 49CFR Part 192.229 (gas service) is acceptable for pipeline work, but is specifically prohibited for compression facility.
When in doubt, destructively test...you can't possibly go wrong this way...
Having said all that, and you didn't ask this question, procedure qualification is always performed with destructive testing. Additionally, if the application falls under API 1104 Section 12 -Mechanized Welding with Filler Metal Additions, both destrictive eand NDE is required.