After the release of new nuclear safety requirements SSR-2 / 1 (the latest version is 2016 Edition) in 2012, IAEA issued a new guideline SSG-30 “safety classification of structures, systems and components of nuclear power plants” in 2014 proposing a new safety classification method. Subsequently, IAEA published TECDOC-1787 “Application of Safety Classification of Structures, Systems and Components of Nuclear Power Plants” in 2016, which further explained the application of SSG-30. The safety classification method of SSG-30 based on the safety functions and design provisions. An SSC implemented as a design provision should, however, be classified directly because the significance of its postulated failure fully defines its safety class without any need for detailed analysis of the category of the associated safety function. The severity of consequences is divided into three levels (high, medium and low). The high, medium and low consequences are defined by the radiation dose criteria for the public and staff in different plant conditions. In order to classify the structures, systems and components of nuclear power plant, the specific meaning of the definition of high, medium and low “consequences” should be clarified firstly. In this paper, the radioactive dose criteria for the public and staff under different working conditions of nuclear power plant are studied and suggestions are put forward to make SSG-30 more operable when used in nuclear power plant SSCs classification.