共查询到16条相似文献,搜索用时 15 毫秒
1.
《Journal of Nuclear Science and Technology》2012,49(12):1061-1062
ABSTRACTReactor Physics that treat the essentials of how fission nuclear reactors work fundamentally has played important roles in safe operations and design studies of various types of nuclear reactors. From the latest activities in the field of reactor physics, this report summarizes some outstanding researches and developments published in scientific journals, including the Journal of Nuclear Science and Technology and others. 相似文献
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This paper deals with the modeling of RBMK-1500 specific transients taking place at Ignalina NPP: measurements of void and fast power reactivity coefficients, as well as change of graphite cooling conditions transient. The simulation of these transients was performed using RELAP5-3D code model of RBMK-1500 reactor. At the Ignalina NPP void and fast power reactivity coefficients are measured on a regular basis and based on the obtained experimental results the actual values of these reactivity coefficients are determined. Graphite temperature reactivity coefficient at the plant is determined by changing graphite cooling conditions in the reactor cavity. This type of transient is unique and important from the point of view of model validation for the gap between fuel channel and the graphite bricks. The measurement results, obtained during this transient, enabled to determine the thermal conductivity coefficient for this gap and to validate the graphite temperature reactivity feedback model. The performed validation of RELAP5-3D model of Ignalina NPP RBMK-1500 reactor allowed to improve the model, which in the future would be used for the safety substantiation calculations of RBMK-1500 reactors. 相似文献
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在钍铀燃料循环过程中生成的232U的衰变子体具有强放射性,对燃料循环具有重要影响。本工作采用ORIGEN2、SCALE5程序,以及基于Bateman方法编写的程序,分析了在不同条件下,热堆中钍反应生成232U的规律。一般情况下,232U主要由232Th的(n,2n)反应链生成,而在中子能谱更软情况下,230Th对232U生成贡献增大;CANDU型重水堆和压水堆的含钍燃料组件的燃耗计算结果表明,铀中232U含量随燃耗深度增加而变大,同时初始230Th/Thtotal大小直接线性影响卸料燃耗时232U/Utotal或232U/233U。 相似文献
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中子活化分析法研究蕨类植物中稀土元素的分布特征 总被引:4,自引:0,他引:4
用中子活化分析(NAA)方法测定了11种蕨类植物中8个稀土元素(La、Ce、Nd、Sm、Eu、Tb、Yb和Lu)的含量,并研究了稀土元素(REE)在植物体内的分布特征。结果显示,蕨类植物叶中的稀土含量普遍较高。对于采自植物体不同部位的叶子,叶子越老,稀土元素含量越高。经球粒陨石归一化后,发现稀土元素分布模式主要是由母土性质决定的。然而,在植物从土壤吸收及输送过程中,稀土元素发生了某些不同程度的分异现象,分布模式曲线表现出与母土有明显的差异。如土壤中轻重稀土比为9.4,而芒黄叶中轻重稀土比为24—51,表明重稀土不易被植物体吸收输运。 相似文献
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In a working procedure qualification test weld representing a heavy section circumferential reactor pressure vessel (RPV) weld tested in 1968, lower toughness values were observed in the top layer region compared to those found in the filler region. Gleeble simulation, extensive microscopic evaluation, diligent Charpy V-notch testing and modelling of the bead sequence and distribution of alloying elements was applied to explain this effect. It could be revealed that the microstructure of the weld metal is the most important factor influencing the toughness. When an ‘as welded’ microstructure is partly or fully reaustenitised by the adjacent multilayer beads, the microstructure transforms and the toughness increases. In the filler region, 85% of the cross-section consists from transformed microstructure, whereas in the top layer only 20% are transformed. It is quite evident that, accidentally, the notch tip of Charpy samples in 1968 were placed in untransformed microstructures. When the top layer on the inner surface of the RPV is weld cladded by austenitic stainless steel, full transformation occurs and the toughness representing the filler region can be taken into account for safety evaluations. 相似文献
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Total neutron yields and neutron emission rates in the forward direction for 50MeV/u ^18O-ion on thick Be,Cu,Au targets have been measured using an activation technique.The results indicate that neutron yields and emission rates in the forward direction depend on the atomic number of target nuclei,i.e.the lighter target the greater neurtron yield and neutron emission rate.Meanwhile,the neutron yield of ^18O-ion is greater than that of 12C-ion when target nucleus and incident energy per nucleon are identical. 相似文献
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M. V. Fedulov 《Atomic Energy》1967,22(2):112-118
A method is presented for determining the spatial and energy distribution of thermal neutrons within the cells of a heterogeneous reactor. If the effect of the asymmetric part of the scattering cross section on the change in neutron energy is neglected, the problem of determining the integral parameters of a cell may, in many cases, be reduced to the solution of monoenergetic Boltzmarm equations for a certain set of energy values with a subsequent determination of the neutron energy spectrum. The possibility of using an iterative process for refining the results of the first approximation is investigated.Translated from Atomnaya Énergiya, Vol. 22, No. 2, pp. 108–113, February, 1967. 相似文献
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《Fusion Engineering and Design》2014,89(7-8):932-936
Measurement and calculations of long-lived gamma-emitting radionuclide activity forming in the fission reactor fast neutron field were done, for some ITER construction steels. The activation was conducted in fast neutron irradiation channel of the MARIA research fission reactor (Poland). The dimensions of steel samples were 10 mm × 10 mm × 1 mm and mass was approximately 0.8 g. The neutron flux density was measured by means of activation foil method and unfolding technique; fraction of neutrons above 1 keV was 95%. The activation lasted 242 h and cooling took 100 days; the mean neutron flux density was 2.9E12 n/(cm2 s) (neutrons above 500 keV are 53% of total) whereas total fluency 2.53E18 cm−2. The activity measurements were done by means of gamma-ray spectrometry. Activity calculations were done by means of FISPACT-II code using the activation libraries EAF-2010 and TENDL-2011 and experimentally determined neutron flux. Measured activity of long-lived gamma emitting radionuclides was, in average, about 6.3 MBq/g 100 days after activation; the dominant radionuclides were 58Co and 54Mn (about 81% and 14% of total activity respectively). The C/E ratio differs for particular radionuclides and is in the range 0.86–0.92 for 51Cr, 0.93–1.21 for 54Mn, 0.77–0.98 for 57Co, 0.91–1.21 for 58Co, 1.17–1.27 for 59Fe, and 1.75–2.44 for 60Co. 相似文献
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The effect on the spatial neutron flux distribution for both of water and fuel temperature increase as well as the change in the control rod position are presented in the Syrian miniature neutron source reactor (MNSR). The cross-sections of all the reactor components at different temperatures are generated using the WIMSD4 code. These group constants are used then in the CITATION code to calculate the spatial neutron flux distribution at different water and fuel temperatures and different control rod positions using four energy groups. This work shows that the increase in water and fuel temperatures during the reactor daily operating time does not affect the spatial neutron flux distribution in the reactor. The change in the control rod position does not affect as well the spatial neutron flux distribution in the reactor except in the region around the control rod position. 相似文献
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As a result of long-term neutron irradiation, the long-lived 14C is produced in the reactor graphite. The exothermic self-sustaining reaction 3C(graphite) + 4Al + 3TiO2 = 3TiC + 2Al2O3 was proposed for processing of such waste. In doing so, the carbon, including the 14C, is chemically bound in the stable TiC. The reaction products in the C-Al-TiO2 system were investigated both by thermodynamic simulation and experimentally in the course of this work. 相似文献
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The content analysis of radioactive waste and radiation dose evaluation is considered as one of the important factors in the reactor facility design.This kind of buildings consists of the concrete for the most part and uses it as the structure and shield of the building.Generally,the concrete has impurities such as cobalt,europium,nickel,and cesium with specific content depending on the production method or manufacturing company.Dominant radioactive nuclides generated from the fundamental compon... 相似文献
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R.G. Abrefah B.J.B. NyarkoE.H.K. Akaho S. Anim SampongR.B.M. Sogbadji 《Annals of Nuclear Energy》2010
The experimental method (foil activation) was used to determine the neutron fluxes in two outer irradiation channels of the Ghana Research Reactor-1. In the experimental procedure, it was observed that the fluxes rise to a peak before falling and then finally leveling out, axially. Axially and radially, it was also observed that the fluxes in the center of the channels were lower than those on the sides. Radially, the fluxes dipped in the center while they increased monotonically towards the sides of the channels. The results have shown that there are flux variations within the irradiation channels at both axial and radial directions. 相似文献
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I. Strašík E. Mustafin R. Hinca D. Schardt A. Golubev B. Sharkov G. Fehrenbacher H. Iwase G. Mustafina 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2008,266(15):3443-3452
As a preparatory work for constructing the FAIR facility at GSI, samples of stainless steel and copper were irradiated by 950 MeV/u 238U ions and depth-profiles of residual activity were measured by gamma-ray spectroscopy. The isotopes with dominating contribution to the residual activity were identified and their contributions were quantified. In contrast to the previous study performed at lower energies, the activities could no longer be determined from the full-assembly target measurements. Depth-profiling of residual activity of all identified isotopes had to be completed by measurements of individual target foils. The activity contributions were then obtained by integration of the depth-profiles. 相似文献