RESUMEN
Off-line gamma-ray spectrometry was used to accurately measure the Cumulative fission product yields (CFPYs) of fission products in the 235U (n, f) reaction induced by 2.8 MeV neutrons. The 2.8 MeV quasi-monoenergetic neutron beam was produced by the CPNG-600 Cockcroft Walton accelerator at the China Institute of Atomic Energy ï¼CIAEï¼and the gamma spectra were measured by the HPGe γ-ray Spectrometer. After fully considering and revising the sources of uncertainty, high-precision CFPYs of 4 fission products were obtained. This study has important applications in reactor design and operation and is conducive to the establishment of an evaluated nuclear database.
RESUMEN
Room temperature ferromagnetism (RTFM) was observed in unirradiated rutile TiO2 single crystals prepared by the floating zone method due to oxygen vacancy (VO) defects. D-D neutrons mainly collide elastically with TiO2, producing VO, titanium vacancies (VTi) and other point defects; the density and kind of defect is related to the neutron irradiation fluence. D-D neutron irradiation is used to regulate the concentration and type of defect, avoiding impurity elements. As the irradiation fluence increases, the saturation magnetization (Ms) first increases, then decreases and then increases. To verify the origin of RTFM, the CASTEP module was used to calculate the magnetic and structural properties of point defects in TiO2. VO induces a 2.39 µ B magnetic moment, Ti3+ and F+ induce 1.28 µ B and 1.70 µ B magnetic moments, respectively, while VTi induces a magnetic moment of â¼4 µ B. Combining experimental and theoretical results, increases in VO concentration lead to Ms increases; more VO combine with electrons to form F+, inducing a smaller magnetic moment. VO and VTi play a key role and Ms changes accordingly with larger fluence. VO, F+ and VTi are the most likely origins of RTFM.
RESUMEN
The cross-sections of 180W(n,2n)179mW, 186W(n,2n)185mW, 165Ho(n,2n)164mHo, 64Ni(n,alpha)61Fe, 165Ho(n,alpha)162Tb and 51V(n,p)51Ti reactions induced by neutrons around 14 MeV were measured using activation technique and calculated by a previously developed formula in this work. The neutron flux was determined using the monitor reactions 93Nb(n,2n)92mNb and 27Al(n,alpha)24Na, the neutron energies were measured with the method of cross-section ratios for 90Zr(n,2n)89Zr to 93Nb(n,2n)92mNb reactions. The results of this work are compared with data published previously.
RESUMEN
The cross section for the (182)W(n,p)(182(m+g))Ta and (184)W(n,p)(184)Ta reactions has been measured in the neutron energy range of 13.5-14.7MeV using the activation technique and a coaxial HPGe γ-ray detector. In our experiment, the fast neutrons were produced by the T(d,n)(4)He reaction at the ZF-300-II Intense Neutron Generator at Lanzhou University. Natural wolfram foils of 99.9% purity were used as target materials. The neutron flux was determined using the monitor reaction (93)Nb(n,2n)(92m)Nb and the neutron energies were determined using the method of cross-section ratio measurements employing the (90)Zr(n,2n)(89)Zr to (93)Nb(n,2n)(92m)Nb reactions. The results of this work are compared with experimental data found in the literature and the estimates obtained from a published empirical formula based on the statistical model with Q-value dependence and odd-even effects taken into consideration.
RESUMEN
In order to investigate the fission process in more detail, and to compare with the measurement of cumulative fission yields, the fission cross section of the (232)Th(n,x)(89)Rb reaction induced by 14 MeV neutron was measured using the activation technique. In our measurement the neutron flux was determined using the monitor (27)Al(n,α)(24)Na reaction, and the neutron energies were measured by the method of cross-section ratios of (90)Zr(n,2n)(89)Zr to (93)Nb(n,2n)(92m)Nb reactions. The cross sections were deduced as 14.0±0.9 mb at E(n)=14.7±0.3 MeV and 13.2±1.0 mb at E(n)=14.1±0.3 MeV.