The High-Temperature Gas-cooled Reactor (HTGR), recognized internationally as a nuclear power system with fourth-generation safety characteristics, has become a representative of advanced nuclear energy technologies due to its inherent safety, high electrical efficiency, and low radioactive waste generation. However, during its operation, the HTGR produces and releases 14C into the environment. With a half-life of 5730 years, 14C has an exceptionally long presence in the environment, which allows it to spread globally and potentially cause long-term impacts on the biosphere. Therefore, controlling the generation and release of 14C is crucial for both environmental protection and the sustainable development of nuclear energy. Previous studies have shown that the release of 14C from HTGR mainly originates from the neutron activation of 14N in the fuel ball pores, and the amount of 14N in the pores directly affects the amount of 14C produced. However, there is currently a lack of accurate experimental data on the content and distribution of 14N in the fuel ball pores, and the relevant parameters in existing models are largely based on assumptions. Therefore, this study aims to conduct experimental research to measure the content of 14N in the fuel ball pores at different radial positions and estimate the porosity of the fuel balls based on the experimental results. This research will not only help validate the accuracy of current assumptions about porosity and 14N content in the pores, but also provide data support for the optimization of future models. Additionally, this study will contribute to the ongoing development of nuclear energy in terms of environmental protection, providing essential scientific evidence for reducing 14N content in the fuel ball pores, minimizing 14C emissions from HTGR, and enabling safer and cleaner nuclear energy utilization.