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以中国第Ⅱ号快中子脉冲反应堆(CFBR-Ⅱ)为试验平台,采用高功率稳定和多注量点拟合的试验方法测定了典型硅整流二极管的中子辐照实验损伤常数,验证了硅整流二极管的中子辐射损伤规律。试验结果表明:以正向压降为观测效应参数的硅整流二极管对于CFBR-Ⅱ堆泄漏中子能谱的试验损伤常数在3~4×10-15 V.cm2范围,硅整流二极管正向压降随中子注量的变化近似遵从指数增长规律。 相似文献
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本文提出了一个改进的能级密度参数a(E)的形式。通过171个核的中子共振实验资料,用最小二乘法,计算了a(F)中的参量。还分核区进行了计算,着重对锕系核进行了计算和分析。 相似文献
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比起传统的X射线探测方法,快中子对爆炸物的检测更加准确,因而备受各国研究者的重视。利用中子源的快中子共振连续谱,准确计算待测物体的核素比例以达到检测爆炸物的目的。采用蒙特卡罗程序(Monte Carlo N-Particle code,MCNP)结合中子飞行时间(Time of Flight,TOF)方法模拟了4种爆炸物的中子共振谱,通过伴随γ粒子法测量252Cf源TOF谱,并运用L-M(Levenberg-Marquardt)算法对各核素的相对比例进行拟合计算。考虑时间分辨、中子飞行距离、待测物体厚度以及统计涨落对计算结果的影响,提出了更准确的TOF谱测量方法。研究结果表明,在能量分辨率较好的条件下,L-M拟合算法能较为准确地计算爆炸物的核素比例,最大误差不超过10%;能量分辨变差,物体厚度增大都会造成计算误差增大;统计涨落的影响使得该方法对于中子计数有一定的要求,总计数达到106条件下的误差在可接受范围内。通过拟合快中子共振连续谱的方式能够获得物质的精确的核素比例以实现爆炸物的检测,但是要想将这种方法应用到现场测量中还需要进一步的研究。 相似文献
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中子辐射俘获截面及共振参数在核工程设计、核天体物理等研究领域中有重要的应用价值。在中国散裂中子源(CSNS)反角白光中子束线(Back n)上,使用C6D6测量系统开展了169Tm辐射俘获反应测量。通过脉冲高度权重技术、共振吸收法和饱和归一法得到169Tm辐射俘获反应的产额。利用SAMMY程序拟合169Tm的产额数据,得到169Tm在1~100 eV能量区间的共振能量、中子宽度、辐射俘获宽度等共振参数。使用实验测得的共振参数和Reich Moore近似计算了169Tm在1~100 eV能量区间的辐射俘获截面。实验测量结果与ENDF/B Ⅷ.0数据库的推荐值总体符合较好,部分共振参数和截面存在一定的差异。产生这些差异的原因与Back n的源中子能谱结构、能量分辨率、实验本底的精度有关。 相似文献
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《Journal of Nuclear Science and Technology》2013,50(10):1097-1104
The resonance interaction effect between hot sample and adjacent cold core was evaluated in a small sample 238U Doppler effect measurement. For this analysis a collision probability code with an ultra-fine group structure PEACO-X was developed. The previously measured Doppler effect reactivity coefficients at FCA are systematically analyzed by using the PEACO-X code. The results were compared with the conventional calculation results using the SLAROM code. From these results, it was shown that this effect depends on the background cross section for 238U in a core, and also depends on the radius and density of the sample. When this resonance interaction effect is taken into account, the calculated Doppler reactivity worths becomes larger than those using the conventional method and the sample dependency of calculation disappeared. The reliability of Doppler effect calculation was significantly improved. 相似文献
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G. Sibona R. E. Mayer V. H. Gillette C. Bonetto J. R. Granada 《Annals of Nuclear Energy》1991,18(12):689-696
The neutron total cross section of Plexiglass has been measured for energies between 10−3 and 103 eV by the transmission method with pulsed-neutron time-of-flight techniques. A calculation based on a synthetic scattering function shows a very good agreement with the measured values over the entire energy range. This model has been used to evaluate other quantities of interest in moderator design problems, including energy-transfer kernels and thermal neutron diffusion parameters. These experimental and theoretical results are compared with available data for Plexiglass. 相似文献
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核数据处理是连接评价核数据库和中子输运程序的重要接口,其中对不可辨共振能区的处理是核数据处理的关键技术点之一。不可辨共振能区的共振峰极为密集,在物理计算中必须考虑其共振自屏效应,概率表方法是获得不可分辨能区自屏截面的常用方法。Ladder Sampling方法是目前使用最广泛的概率表产生方法,该方法通过构造随机共振序列等效真实共振结构来统计概率表。基于Ladder Sampling方法在NECP-Atlas程序中开发了概率表计算模块,对计算过程中的复误差函数计算、卡方随机数产生、概率表划分、共振公式选取、Ladder数目以及排序算法进行了敏感性分析,最终确定了最优的计算方法,实现了概率表的精确、高效效率。 相似文献
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Dielectronic recombination is an important process in high temperature plasmas.In the present work,the KLn (n =L,M,N and O) DR resonance strengths of He-like to O-like xenon ions are measured at the Shanghai electron beam ion trap using a fast electron beam energy scanning method.The experiment uncertainty reaches about 6% with significant improvement of statistics.A relativistic configuration interaction calculation is also made.Theoretical results agree with the experiment results within 15% in most cases. 相似文献
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基于NECP-X程序中已经研发的全局-局部耦合共振计算方法,研究了针对非棒状几何燃料的共振计算方法。首先,采用中子流方法计算真实问题的丹可夫修正因子,以处理全局的空间效应;其次,基于丹可夫修正因子等效获得小规模问题周围慢化剂的几何信息;最后,对于小规模问题燃料区的有效自屏截面的计算采用共振伪核素子群方法。将该方法应用于非棒状几何燃料数值计算,结果表明,该方法在处理非棒状几何燃料栅元的共振计算时,与蒙特卡罗结果程序相比,微观吸收截面偏差不超过1.8%,无限介质增殖因数偏差不超过110 pcm(1 pcm=10-5),具有较高的计算精度;在大规模问题的计算中,基于板状燃料的JRR-3M实验堆全堆在整个燃耗过程有效增殖因数偏差均在300pcm左右,组件功率偏差在整个燃耗过程不超过0.62%。因此,本研究提出的共振计算方法具有较高的正确率和精度。 相似文献
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Based on the combination of subgroup method and characteristics method, a resonance self-shielding calculation code SGMOC is programmed. SGMOC code can handle the complex (both in geometry and resonant components) resonance problems. The numerical results are in good agreement with those of MCNP. In order to improve the SGMOC calculation accuracy, two techniques are utilized, i.e., the resonance interference effects between resonant nuclides are considered, and on the other hand, the elastic scattering resonance is taken into account. These two techniques can enhance the accuracy remarkably. 相似文献
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用贝叶斯定理从可分辨共振参数估算平均能级间距。此法充分利用能级间距和宽度分布提供的信息,对测量样本的弱能级丢失做比较精确的修正,因而获得比较好的平均能级间距的估值。我们已完成了S波的计算,并与其它工作进行了比较。 相似文献
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《核技术(英文版)》2016,(2):122-130
An improvement for application of Dancoff factor is developed. It combines Stamm'ler's two-term method for resonance integral calculation with neutron current method for Dancoff factor calculation. Stamm'ler's formulation, which is originally derived for the infinite lattice geometry, can be easily revised to contain the Dancoff factor explicitly, while the neutron current method can easily calculate the Dancoff factor for general irregular assembly geometry. For the resonance interference effects the resonance interference factor table is built in pairs of nuclides, only for the interference between 238 U and other resonance nuclides, spanning over a range of background cross-section and number density ratio of the pairing nuclides. A series of verification calculations have been carried out for problems of infinite lattice and single assembly geometry, with two or multiple resonance absorbers. For these verification calculations, our improvement on Dancoff factor application and resonance interference give good results. 相似文献