Abstract: Radiographic tests by using Se75 ray source were used to verify the detection penetrameter sensitivity for nuclear power plant of thin-walled piping welds. By comparing the photographic characteristics of Se75 with Ir192 ray source, as well as photographic sensitivities for different radiation sources to meet the RCC-M The Design and Construction Rules Applicable to Mechanical Components of PWR Nuclear Islands specifications, applicable thickness rang of Se75 radiography was proposed, verified the photographic sensitivity while using Se75 ray source with different types of film and intensifying screen together to meet the RCC-M specification. The applicable radiographic film types while using Se75 ray source were recommended.