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堆芯热通道因子是堆芯热工设计及安全分析的一项重要参数,确定热通道因子需用中子学计算给出较准确的燃料组件内元件棒功率分布。在三维六角形几何节块扩散理论基础上,使用多项式重构的方法计算节块内中子通量密度分布和功率密度分布。针对快堆六角形燃料组件的特点,用小六角形积分的方法计算组件内元件棒功率,得到组件内各元件棒功率分布。在NAS程序基础上,编制了元件棒功率分布计算模块NAS PIN。通过与蒙特卡罗程序的校验可发现,二者计算结果符合较好,计算精度可满足工程设计的需要。 相似文献
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在计算效率上,节块法加组件精细分布重构方法很有吸引力;而另一方面,采用不在子理论能使爱量精细分布更合理、更准确。本文通过直接用多项式展开方法来拟合细网扩散差分方程得出的组件通量分布,验证基于多项式展开的节块法组件精细分布重构方法的有效性和适应性。通过验算发现,在常规扩散方程的意义下,精细分布重构方法的精度在重要燃普组人可满足工程需要;但采用不连续因子修正扩散方程后,堆芯外围的组件以及相邻组件参数变 相似文献
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为了在压水堆(PWR)中限制控制棒尖齿效应,燃料管理计算程序系统NECP-Bamboo中的变分节块法(VNM)在之前的工作中通过将截面用分片多项式展开,具备了处理非均匀截面的能力。但半插的控制棒同时在节块表面带来了非均匀的不连续因子(DF)。本文提出了一个可以完全解决这个问题的方案。首先,通过包含非均匀不连续因子的表面积分将非均匀不连续因子显式地表达在变分节块法的泛函中,然后用分片多项式展开不连续因子,使其出现在响应矩阵的构建中。与现有的再均匀化方法相比,BEAVRS基准题的数值结果表明,含非均匀不连续因子的非均匀变分节块法可以消除控制棒尖齿效应,同时获得更准确的功率分布。 相似文献
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在采用调制法进行组件精细功率重构时,由于改进的格林函数节块法程序引入了组件不连续因子,导致重构时角点中子通量不连续,需引入角点不连续因子进行修正保证其连续性。文中利用改进格林函数节块法程序堆芯扩散计算的结果,采用高阶多项式展开的调制法来进行组件内的精细功率重构,探讨了角点不连续因子在精细功率重构中的重要作用。并通过秦山二期实际堆芯的两种工况对其进行了验证,与SIMULATE-3的计算结果对比表明:考虑角点不连续因子的精细功率重构具有较高的计算精度,能够满足工程计算的要求。 相似文献
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本文简要地叙述了用 INCA 法将固定的堆内自给能探测器的“读数”拟合成轴向功率分布曲线,提出了将固定的有限长度的自给能探测器的“读数”经简化处理后就可将拟合函数为 x 的4次多项式的最小二乘法进行曲线拟合。选择典型的功率分布曲线,用 INCA 法、拟合函数为 x 的4次多项式最小二乘法和二次样条函数法处理,并比较其结果。考虑了格架的影响后,用拟合函数为 x 的4次多项式的最小二乘法得到的结果是好的,它的计算比样条函数法简单。用这方法还可省去长钒自给能探测器。 相似文献
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本文叙述了局部精细分布计算的数学模型和数学处理,并给出了数值分析结果。该方法以粗网格展开法为基础,首先由粗网计算获得节块界面入射中子流,然后用有限差分方法在节块内部解一个具有固定源的中子扩散问题,从而获得节块内部通量和功率的精细分布。 相似文献
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为了研制高性能燃料组件,定位格架的阻力特性直接关系到燃料组件的热工性能和水力相容性。本文针对5×5规模的定位格架,从流动阻力的基本原理出发,利用CFD方法研究并建立了格架局部阻力特性的理论计算模型,并对计算结果进行验证。结果表明,基于计算模型获得的格架局部阻力系数与直接模拟结果基本一致,验证了计算模型的准确性。 相似文献
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A new method is proposed for calculating non-uniform LWR lattices. The method is based on some reasonable assumptions. A new fine-mesh algorithm is derived for the global reactor calculation. The balance equation can be considered as the generalization of the finite-difference form of the diffusion equation. Its coefficients are response matrix elements instead of the traditional homogenized macroscopic cross-sections. As not only cell boundary quantities but also cell-averaged reaction rates (including average flux) are connected with each other by response matrices, on solving the balance equation not only is the fine-mesh flux distribution obtained but also the effective cell parameters. The response matrix elements are obtained from cylindricalized cell transport calculations. In the proposed method several transport problems with different boundary conditions are to be solved for each cell type. The cell transport calculations and the global reactor calculation are coupled in a consistent manner. 相似文献
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《Journal of Nuclear Science and Technology》2013,50(11):1162-1168
A modified quasi-steady-state method has been developed in order to evaluate the mean power during a nuclear excursion in fissile solution. The conventional method used the critical equation based on the one-group theory in order to calculate the reactivity. However, the one-group approximation reduces the calculation accuracy, and the geometrical buckling used in the critical equation is not applicable to complex geometries. Thus, we have modified the method to use the reactivity feedback coefficients, which are widely used in the calculation of one-point reactor kinetics. Although the modified method requires an external calculation to obtain the feedback coefficients, it is applicable to complex geometries and provides more accurate results than does the one-group approximation when the proper coefficients are given. Moreover, a new method to calculate the boiling power has been developed. In this method, the power corresponding to the void fraction that compensated for the inserted reactivity along with the temperature feedback was calculated using the relationship, which was derived using the French SILENE experimental data. Experimental analyses have been conducted to validate the new method for the French CRAC and Japanese TRACY experiments. The analytical results showed close agreement with the experimental results. 相似文献
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《Journal of Nuclear Science and Technology》2013,50(8):681-683
A new method has been established to calculate sensitivity coefficients of cell parameters based on generalized perturbation theory using the collision probability method. The proposed method does not require the calculation of the changes of collision probabilities due to cross section changes, so it is as powerful as the commonly used generalized perturbation theory in diffusion theory, We demonstrate the validity of the method by comparing the calculated sensitivity coefficients with those obtained from the direct cell calculations. AS an application, we calculate the sensitivity coefficients of neutronic properties in cells with different moderator to fuel volume ratios, and discuss the physical meaning of the difference between the sensitivity coefficients. 相似文献
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双示踪剂Micro-PET显像评价大鼠心肌缺血模型 总被引:1,自引:0,他引:1
采用左前降支结扎法建立大鼠心肌缺血模型,氯化三苯基四氮氮唑(TTC)染色法作为金标准,比较传统方法(结扎后心电图T波改变)和Micro PET方法(13NH3·H2O和18F-FDG联合显像)评价此模型成功的准确性.12只大鼠进行结扎手术,9只经心电图显示T波改变,视为建模成功;Micro-PET结果显示,建模前12只大鼠心肌摄取均匀,心肌摄取13NH3·H2O和18F-FDG的标准摄取值分别为3.78±0.59和2.30±0.21,建模后,仅6只出现心肌灌注和代谢异常,心肌摄取13NH3·H2O和18F-FDG的标准摄取值分别为2.78±0.46和1.65±0.21;TTC染色法验证Micro-PET评价方法的准确率为100%,而传统T波改变法的准确率为66.67%.结果表明,Micro-PET显像评价心肌缺血模型更准确、更客观. 相似文献
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压水堆燃料组件输运燃耗耦合计算通常采用的是传统的预估-校正(PC)燃耗方法。然而,该方法本身的假设导致其存在一定的计算误差。为进一步提高燃耗计算的精度,本文针对传统的预估-校正燃耗方法的缺陷研究了改进的预估-校正燃耗方法,改进了对核反应率进行修正的高阶预估-校正燃耗方法,并在Bamboo-Lattice程序中进行了程序实现,对该方法进行了验证分析。结果表明:改进的预估-校正燃耗方法和高阶预估-校正燃耗方法在保证计算效率的前提下提高了燃耗计算的精度。 相似文献
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Perturbation theory formulas for the effect of the dimensions on the critical mass in a fast reactor
S. B. Shikhov 《Atomic Energy》1960,6(2):90-94
This paper deals with a method for calculating the critical mass of a reactor provided with a sufficiently thick reflector as a function of the composition of the core and its dimensions.The working formula is obtained by an application of the theory of similarity to the usual first-approximation scheme of perturbation theory. For the calculation of the coefficients of the formula it is necessary to have the spatial and energy spectra of the neutron fluxes and values calculated numerically for some fixed volume of the reactor with a sufficiently thick reflector. By means of the coefficients so obtained for the formula it is possible to predict the critical mass over a wide range of variation of the dimensions of the core (over a change by about a factor two).If the size of the core goes beyond the limits of the interval thus accessible, one has to calculate the coefficients for a new range of the dimensions, and this requires a new numerical computation of the spectra.In this paper we give a formula containing coefficients calculated for a certain typical spectrum of a fast reactor for a number of isotopes contained in the core. The formula is checked by a nine-group calculation for volumes of the core ranging from 200 to 1000 cubic decimeters. The constants for the nine-group calculation were obtained from Soviet and foreign material published up to 1955.In conclusion the writer thanks Active Member of the Academy of Sciences of the Ukrainian SSR A.I. Leipunskii, G.I. Marchuk, and L.N. Usachev for a discussion of the work. 相似文献