Background: Gamma ray from the decay of 16N in main coolant of PWR is one important factor for radiation protection.Purpose: This paper attempts to develop a 16N specific activity calculating method based on the core neutron flux rate distribution.Methods: Firstly

the activation yield and the decay balance theory of 16N in main coolant of PWR were analyzed.A16N specific activity calculating model based on sum of fluid channels in core was founded.The model made use of velocity of flow and average neutron flux rate in the fluid channels as input data.The steady 16N specific activities in main coolant while the reactor running could be calculated using this model.Subsequently

the model was practiced using Qinshan-2 NPP data.The reactor core was modeling in MCNP accurately.Neutron flux rate distribution in the core was calculated via MCNP simulation.The neutron flux rate data was used as input parameter of the calculating model

and the integrative calculation of 16N specific activity in main coolant was completed.Results: Result of the calculation was Aout=3.34×106Bq/cm3.Tt well matched the referenced value of 3.28×106Bq/cm3.Conclusions: The method was useful to calculate the16N specific activity.