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利用MCNP程序建立了CFBR-Ⅱ堆结构的三维模型,借助中子倍增的方法实现了计算中子价值的功能.为消除实验中用中间钢托盘孔道内的中子价值代替上下半球的中子价值而引起的差异,利用均匀抽样技巧对各区域沿径向分层细致计算.结果表明,中子价值最大处位于高富集度铀区域中间某层而非系统中心或上下半球球心,其他区域中子价值则沿径向单调递减. 相似文献
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In this work,we developed a numerical analysis-associated experiment method to determine the effective multiplication factor k_(eff),which is difficult to obtain directly from conventional neutron source multiplication(NSM)method.The method is based on the relationship between k_(eff),subcritical multiplication factor k_s and external neutron source efficiency Φ~* in the subcritical system.On basis of the theoretical analysis,the dependence of k_s and Φ~* on subcriticality and source position was investigated at the Chinese Fast Burst Reactor-Ⅱ(CFBR-Ⅱ).A series of k_s were measured by NSM experiments at four subcritical states(k_(eff) = 0.996,0.994,0.991 and0.986) with the ~(252)Cf neutron source located at different positions(from the system center to outside) at each subcritical states.The Φ~* was obtained by Monte-Carlo simulation for each condition.With the measured k_s and calculated Φ~*,k_(eff) of the subcritical system was evaluated with a relative difference of 1%between values obtained by the improved method and by positive period method.Especially,the relative difference of 0.18%with the source located at the system center. 相似文献
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为提升快中子临界装置的实验能力,在实验大厅旁边扩建了附属建筑物,在实体连接位置形成了一个样品传输通道。为了保证工作人员的辐射安全,需要对通道进行屏蔽。采用蒙特卡罗方法进行屏蔽门的物理设计,确定了含硼石蜡为中子屏蔽材料,不锈钢为光子屏蔽材料。为保证硼在石蜡层上的均匀分布,防止石蜡内部形成空洞,采用了分层分次工艺进行屏蔽门浇铸。为保证屏蔽门对通道的有效覆盖,采用了分步工艺进行安装。辐射剂量监测结果表明,人员日常工作区域的辐射有效剂量为0.125 mSv/a,小于建设项目管理目标值2 mSv/a,远小于《电离辐射防护与辐射源安全基本标准》规定的放射性工作人员年剂量限值20 mSv/a,屏蔽门的研制满足设计和使用要求。 相似文献
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