分类： 核科学技术 >> 辐射物理与技术 提交时间： 2025-03-10
摘要： Colloids are prevalent in nuclear waste repositories, with bentonite colloids posing an uncontrollable riskfactor for nuclide migration processes. In this study, static adsorption experiments were coupled with dynamicshower experiments to comprehensively investigate the influence of bentonite colloids on Sr2+ migration ingranite, considering adsorption capacity. Bentonite colloids have a considerably greater adsorption capacity thanboth bentonite and granite, with a maximum adsorption of 30.303 mg/g. The adsorption behavior of bentonitecolloids on Sr2+ is well described by the Langmuir isotherm and pseudo-second-order kinetic models, indicatingthat a single-layer chemical adsorption process is controlled by the site activation energy. The adsorbed Sr2+is unevenly distributed on the colloids, and the adsorption mechanism may involve ion exchange with Ca.Bentonite colloids exhibit superior adsorption in neutral environments. The cations in groundwater inhibit Sr2+adsorption, and the inhibition efficacy decreases in the order Fe3+>Ca2+>Mg2+>K+ . The presence of bentonitecolloids in a granite column slightly influences the retention of Sr2+ in the column while markedly reducingthe Sr2+ penetration time from 70 h to 18 h. However, the coexistence of Co2+, Ni2+, and Cs+ in a multinuclidesystem weakens the ability of the colloids to promote Sr2+ migration. In comigration of colloid and multinuclidesystems, the adsorption of nuclides by bentonite colloids causes the nuclide migration speed to decrease in theorder Sr2+>Cs+ >Ni2+>Co2+. This study provides insights into Sr2+ migration in cave repositories for low- andmedium-level radioactive waste.
分类： 核科学技术 >> 核材料与工艺技术 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： Diffusion behaviors of Se(IV) and Re(VII) in bentonite were investigated by a through-diffusion method in nitrate, sulfate, carbonate and silicate solutions. SEM-EDS analysis showed that Se(IV) was reduced to red precipitate Se(0) by sulfite. Se(IV) was sorbed on bentonite with distribution coefficient Kd of (2.65.3)10-4 m3/kg in sulfite, nitrate and sulfate solutions, whereas it was hardly sorbed in carbonate and silicate solutions. The effective diffusion coefficients were De= (0.817.0)10-11 m2/s for Se(IV) and De= (1.44.4)10-11 m2/s for Re(VII). The De value of Se(IV) exhibited a dependence on the inorganic salts in the order of sulfite nitrate sulfate > silicate > carbonate, whereas the salts had insignificant effect on Re(VII) diffusion. The results suggest that the discrepancy in diffusion mechanism may lead to the different impact of the salts on the diffusion of Se(IV) and Re(VII) in GMZ bentonite.
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-10-24
摘要： Light Gradient Boosting Machine (LightGBM) and Random Forest (RF) algorithms were used to predict the apparent diffusion coefficient of Se(IV) in compacted bentonite.Seven instances of Se(IV)were measured using through-diffusion method.LightGBM (R2= 0.98 and RMSE = 0.025) exhibited superior predictive accuracy with a trainingdataset consisting of 956instances and eight input featuresfrom Japan Atomic Energy Agency(JAEA-DDB).Shapley Additive Explanation and Partial Dependence Plots analysesrevealedvaluable insightsinto the diffusion mechanism of adsorbed anion obtained by evaluating the relationshipsbetween the apparent diffusion coefficient and the dependency of each input feature.
分类： 核科学技术 >> 核材料与工艺技术 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： The effect of humic acid (HA) on the diffusion of Re(VII) was investigated in compacted Gaomiaozi (GMZ) bentonite by the through- and out- diffusion method. The effective diffusion coefficient, De, and accessible porosity, acc, were measured in order to evaluate the impact of humic acid on Re(VII) diffusion. The De value was in the range of (5.28.3)10-12 m2/s. The diffusion of Re(VII) was enhanced in the presence of HA, and the De value increased with the increase of ageing time, indicating that the formation of HA-Re complexes was slow. Moreover, the acc was in the range of (0.06 0.16), which is less than the total porosity. It implies that the HA-Re complexes are anions.
分类： 环境科学技术及资源科学技术 >> 环境科学技术基础学科 提交时间： 2019-12-06 合作期刊: 《干旱区科学》
摘要： Excessive fertilization combined with unreasonable irrigation in farmland of the Hetao Irrigation Area (HIR), China, has resulted in a large amount of nitrogen (N) losses and agricultural non-point source pollution. Application of soil amendments has become one of the important strategies for reducing N losses of farmland. However, there is still no systematic study on the effects of various soil amendments on N losses in the HIR. In this study, three types of soil amendments (biochar, bentonite and polyacrylamide) were applied in a maize–wheat rotation system in the HIR during 2015–2017. Yields of maize and wheat, soil NH3 volatilization, N2O emission and NO3– leaching were determined and soil N balance was estimated. The results showed that applications of biochar, bentonite and polyacrylamide significantly increased yields of maize by 9.2%, 14.3% and 13.3%, respectively, and wheat by 9.2%, 16.6% and 12.3%, respectively, compared with the control (fertilization alone). Applications of biochar, bentonite and polyacrylamide significantly reduced soil N leaching by 23.1%, 35.5% and 27.1%, soil NH3-N volatilization by 34.8%, 52.7% and 37.8%, and soil N surplus by 23.9%, 37.4% and 30.6%, respectively. Applications of bentonite and polyacrylamide significantly reduced N2O-N emissions from soil by 37.3% and 35.8%, respectively, compared with the control. Compared with application of biochar, applications of bentonite and polyacrylamide increased yields of maize and wheat by 5.1% and 3.5%, respectively. Our results suggest that soil amendments (bentonite and polyacrylamide) can play important roles in reducing N losses and increasing yield for the maize–wheat rotation system in the HIR, China.
分类： 物理学 >> 核物理学 提交时间： 2025-01-12
Tian, Mr. Junlei
Feng, Mr. Jiaxing
Shen, Mr. Jiacong
Yao, Mr. Lei
Wang, Mr. Jingyan
WU, Dr. Tao
zhao, Dr. Yaolin 赵耀林
摘要： Missing values in radionuclide diffusion datasets can undermine the predictive accuracy and robustness of machine learning (ML) models. A regression-based missing data imputation method using light gradient boosting machine (LGBM) algorithm was employed to impute over 60% of the missing data, establishing a radionuclide diffusion dataset containing 16 input features and 813 instances. The effective diffusion coefficient (De) was predicted using ten ML models. The predictive accuracy of ensemble meta-models, namely LGBM-extreme gradient boosting (XGB) and LGBM-categorical boosting (CatB), surpassed the other ML models, with R2 values of 0.94. The models were applied in predicting the De values of EuEDTA- and HCrO4- in saturated compacted bentonites at compaction ranged from 1200 kg/m3 to 1800 kg/m3, which was measured using a through-diffusion method. The generalization ability of LGBM-XGB model surpassed that of LGB-CatB in predicting the De of HCrO4-. Shapley additive explanations identified the total porosity as the most significant influencing factor. In addition, the partial dependence plot analysis technique showed clearer results for univariate correlation analysis. This study provides a regression imputation technique to refine radionuclide diffusion datasets, offering a deeper insight into analyzing the diffusion mechanism of radionuclide and supporting the safety assessment of the geological disposal of high-level radioactive waste.
分类： 物理学 >> 核物理学 提交时间： 2024-12-03
Tian, Mr. Junlei
Feng, Mr. Jiaxing
Shen, Mr. Jiacong
Yao, Mr. Lei
Wang, Mr. Jingyan
WU, Dr. Tao
zhao, Dr. Yaolin 赵耀林
摘要： Missing values in radionuclide diffusion datasets can undermine the predictive accuracy and robustness of machine learning (ML) models. A regression-based missing data imputation method using light gradient boosting machine (LGBM) algorithm was employed to impute over 60% of the missing data, establishing a radionuclide diffusion dataset containing 16 input features and 813 instances. The effective diffusion coefficient (De) was predicted using ten ML models. The predictive accuracy of ensemble meta-models, namely LGBM-extreme gradient boosting (XGB) and LGBM-categorical boosting (CatB), surpassed the other ML models, with R2 values of 0.94. The models were applied in predicting the De values of EuEDTA- and HCrO4- in saturated compacted bentonites at compaction ranged from 1200 kg/m3 to 1800 kg/m3, which was measured using a through-diffusion method. The generalization ability of LGBM-XGB model surpassed that of LGB-CatB in predicting the De of HCrO4-. Shapley additive explanations identified the total porosity as the most significant influencing factor. In addition, the partial dependence plot analysis technique showed clearer results for univariate correlation analysis. This study provides a regression imputation technique to refine radionuclide diffusion datasets, offering a deeper insight into analyzing the diffusion mechanism of radionuclide and supporting the safety assessment of the geological disposal of high-level radioactive waste.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-05-02
Sheng, GD [Sheng, Guodong][ 1,3,4,5 ]
Alsaedi, A [Alsaedi, Ahmed][ 4 ]
Shammakh, W [Shammakh, Wafa][ 4 ]
Monaquel, S [Monaquel, Shatha][ 4 ]
Sheng, J [Sheng, Jiang][ 2 ]
Wang, XK [Wang, Xiangke][ 1,4 ]
Li, H [Li, Hui][ 1 ]
Huang, YY [Huang, Yuying]
摘要： n this paper, nanoscale zero-valent iron (NZVI) immobilized on carbon nanotube (CNT) composite (NZVI/CNT) was prepared, characterized and used for the sequestration of Se(IV) in water. The structural analysis revealed that NZVI were uniformly immobilized on CNT surfaces, and thus the oxidation and aggregation of NZVI was obviously minimized. Compared to bare NZVI, the NZVI/CNT exhibited much higher efficiency on Se(IV) sequestration due to the good synergistic effect between CNT adsorption and NZVI reduction. The results from X-ray absorption fine structure (XAFS) revealed that Se(IV) could be almost completely reduced into Se(0)/Se(-II) by NZVI/CNT, while partial reduction occurred on NZVI with a trace of Se(IV) adsorbed on the corrosion products. Besides, the role of pH in Se(IV) sequestration on NZVI/CNT was lower than that on NZVI due to the buffering effect of CNT. Moreover, CNT immobilization could also weaken the inhibition effect of humic acid (HA) on the removal of Se(IV) by NZVI, since CNT showed strong adsorption for HA that blocks potential reactivity. The excellent performance of NZVI/CNT offer a promising material for detoxification of Se(IV) from wastewater.
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