Abstract: Collective dose is one of the important indicators of nuclear power operation performance, and it needs to be promoted to a favourable downward trend through management measures and technical means. Reducing collective dose is an important embodiment of following the principle of radiation protection optimization. The factors that affect the collective dose are not only of wholeprocess, including the design of nuclear power plants, equipment manufacturing and installations, unit debugging and operation stage control, etc.; but also omni-directional, with the control of radiation sources, the annual overhaul workload, and the efficiency of maintenance work involved. Through the combing and analysis of the factors influencing collective dose, we summarises that reducing the collective dose of nuclear power plants can be achieved mainly via source item control (for example, by implementing the replacement of easy-activated materials of primary-circuit equipments, water chemical control to reduce the corrosion of primary-circuit equipments, upgrading primary-circuit water filter elements to improve the purification efficiency, and other measures.) and the control of radiation working hours (such as optimising and extending the maintenance cycle of equipments through the optimisation and adjustment of the maintenance outline; improving the reliability of equipments and reducing their failure rate to reduce the maintenance workload; improving staff skills, improving work efficiency through the application of mechanisation and intelligent technology, etc.). Anyway, sufficient attention should be paid to organizational management and the support of management policies, for both the control of source terms and radiation work hours.

Key words: Pressurised water reactor nuclear power plant, Collective dose, Control, Radiation source items, Working hours