Seems there is no particular software for RT film interpretation. Almost is on handbook (Agfa e.g), or in NDT Training Doc. For interpretation, it almost will be based on the expert experience.
For acceptable limits for the defects, there is a lot International Codes/Standards ( ASME Code like ASME I, VIII, B31.1, B31.3, B31.8, API 1104, API 650, AWS D1.1....). It's depended on your applied code to the test object, equipment.
Regards
Howard
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There's nothing difficult, just afraid not much money. Mountain cutting and Ocean backfilling, if couldn't, so hire