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: 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: In this paper, a new model is proposed to calculate distribution of fission products in particles of different sizes. The model sensitivity to the effective volume and mass of vaporized soil particles is examined. Compared with other fractionation models, the new method has a much better performance in calculating r89,95, but the calculated cumulative activity fraction for particles in diameters over 100 m is in between the results using the F-T and G-X models. It is concluded that in a near surface nuclear explosion radioactivity is mainly distributed in soil particles which have not been vaporized, and according to the Henrys law and ideal gas law, r89,95 may vary in larger particles when effective volume of the fireball is changed.
分类: 核科学技术 >> 裂变堆工程技术 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: Neutron spectrum should be measured before test samples are irradiated. Neutron spectrum in an irradiation chamber of a research reactor was measured by using activation method when the reactor is in normal operation under 2 MW. Sixteen kinds of non-fission foils (19 reaction channels) were selected, of which 10 were sensitive to thermal and intermediate energy regions, while the others were of different threshold energy and sensitive to fast energy regions. By measuring the foil radioactivity, the neutron spectrum was unfolded with the iterative methods SAND-II and MSIT. Finally, shielding corrections of group cross-section and main factors affecting the calculation accuracy were studied and the uncertainty of solution was analyzed using the Monte Carlo method in the process of SAND-II.