材料期刊网

准确测量并计算稀土尾矿砂的放射性活度浓度及其变化规律对制定相应的豁免标准和日后的处理处置具有重要的意义。根据选取的特征γ射线，分析对比平衡与非平衡状态下铀系、钍系、锕系三个天然衰变系的总活度浓度，结合衰变链的一般动力学方程，计算总放射性活度与每个核素的放射性活度，并研究钍系各核素在平衡被不同程度破坏的情况下随时间的变化规律。结果显示，按照非平衡情况下计算得出的总α和总β放射性活度浓度比平衡情况下的更接近实际测量结果，此外，钍系核素在平衡被破坏后的放射性活度随时间变化情况与母体和228Ra的初始放射性活度浓度有关，若228Ra小于232Th，则总放射性活度在60 a再次平衡后达到最大值，为10倍的母体活度；若228 Ra大于232 Th，则总放射性活度在3.82 a出现最大值，为4.57倍母体活度与5.25倍第一子体228 Ra的初始活度浓度之和。因此，可知稀土尾矿砂放射性活度已经遭到破坏，其总活度浓度应该采用非平衡情况下的几个特征核素的活度浓度共同计算得到，并且需计算分析其随时间变化出现的最大值，以此来确定是否超过相关法规标准。

It is of great significance to measure and calculate rare earth tailing radioactivity for the develop-ment of appropriate standards and exemption disposal. The total activity concentration of the three natural decay series (uranium series, thorium series, actinium series) was analyzed under the equilibrium and disequi-librium state according to the selected characteristic γ-rays. At the same time, we calculated the total activity concentration and the radioactivity for each radionuclide based on the general kinetic equations of decay chain and studied the trend of each radionuclide of thorium-series under different degrees of disequilibrium with time. The results demonstrated that the total radioactivity of α and β calculated in disequilibrium state was more closed to the actual measurement results compared to that in equilibrium state. In addition, the activity changes with time of thorium series in disequilibrium state are related to the initial activity concentration of the mother nuclide and 228Ra. If the activity concentration of 228Ra is less than that of 232Th, the total activity peak will be 10 times to maternal activity and appear after 60 a when the thorium series become balance again. If the activity concentration of 228Ra is greater than that of 232Th, the maximum total activity will appear in 3.82 a, and will be the sum of 4.57 times of the initial activity concentration of the mother nuclide and 5.25 times of the initial activity concentration of the first daughter 228Ra. Therefore, the rare earth tailings have been in disequilibrium state, and its total activity concentration should be determined based on the activity concentration of several feature radionuclides. In addition, the maximum value of the activity concentration is profitable to judge whether the activity concentration is fit with relevant regulations and standards.