Analysis of Radioactivity Levels in Finished Cement in Chongqing

During the cement production process, certain materials with relatively high levels of natural radioactivity are commonly incorporated. Without control, this may lead to a residential environment with prolonged elevated radioactivity, posing a potential threat to human health. In this study, a systematic investigation of radioactivity levels was conducted on cement samples from the three major regions of Chongqing: the main urban area, northeastern Chongqing, and southeastern Chongqing. Key parameters, including the activity concentrations of the radionuclides ²²⁶Ra, ²³²Th, and ⁴⁰K; external hazard index; internal hazard index; the radium equivalent activity; and the additional annual effective dose from external gamma radiation, were calculated. X-ray fluorescence (XRF) analysis was also performed to examine the chemical composition of typical samples. The research findings indicate that all 57 tested cement samples from 20 plants complied with the radiation safety requirements. Among the sampled products, the radioactivity levels followed the order: main urban area > northeastern region > southeastern region. Specifically, the mean radium equivalent activity of samples from the main urban area was approximately 13.85% and 31.43% higher than those from northeastern and southeastern Chongqing, respectively. Statistical tests indicated that this regional difference was mainly driven by ²²⁶Ra, while ²³²Th and ⁴⁰K showed no significant regional differences. Through XRF analysis of cement products and mineral raw materials with varying radioactivity levels, combined with Pearson correlation analysis, the radium equivalent activity was found to be positively correlated with the contents of TiO₂ and ZrO₂. Further analysis of individual radionuclides suggested that this correlation was mainly driven by ²³²Th, with a secondary contribution from ²²⁶Ra, whereas ⁴⁰K showed no significant correlation. These results provide supporting data for evaluating the natural radioactivity levels in cement products from Chongqing.