蒙特卡罗法模拟γ谱仪无源效率刻度

介绍了蒙特卡罗模拟和分析计算相结合对γ谱仪进行无源效率刻度的方法。针对点源情况下不同探测器厚度、半径及源探距等几何条件,以及不同面源半径的面源,以蒙特卡罗模拟获得γ谱仪无源效率刻度效率数据作为基准,结合插值法和积分计算,从而实现无源效率刻度。并初步编写了一套与该方法配套无源效率刻度软件。将软件计算结果与蒙特卡罗模拟结果比较,最大相对误差为9.1%。     

航空伽玛谱仪校准因子的计算研究

为了确定不同高度飞行时航空伽玛谱仪对大面积伽玛源的校准因子,采用蒙特卡罗方法模拟了航测模型源和无限大地面源在机载NaI探测器上的计数响应过程,给出了标定高度1m处的计数响应能谱,得到了不同高度飞行测量时谱仪对地面无限大137Cs源的校准因子,计算结果和实验标定结果符合较好.     

几何因子对低脉冲辐射测量的影响

在弱脉冲辐射测量中,脉冲源尺寸、探测器灵敏体积和测量距离等几何因子对测量结果产生了很大的影响。根据目前的科研需求,模拟脉冲源与探测器的空间布局,导出几何因子物理公式。根据实验工作环境,运用数学方法,对物理公式中的源尺寸因子作等效处理,设置了计算中的偏差上限。结合实验工作,对实验现场脉冲源与探测器的测试空间布局进行了数值模拟计算,为目前某测试项目提供了参考数据。     

HPGeγ谱仪峰总比不变性的实验研究

测定了点源、面源和盘状源在距HPGe探测器表面不同距离上的峰总比，研究了探测器的峰总比随样品形状和测量几何条件的变化规律，验证了同一探测器不同测量条件下峰总比基本不变的特性，给出了所使用HPGeγ谱仪的峰总比曲线。      

磁谱β仪大面积源的静电补偿和几何修正

测量电子反中微子静止质量的最灵敏的方法是测量氚的β谱。采用大面积源能在保持β谱仪高分辨率的情况下,显著提高谱仪的亮度。利用传输矩阵方法和轨迹跟踪方法,分别在二级近似和高级近似下研究了大面积源的静电补偿和几何修正。计算了面源和面源上等位线的理想形状,讨论了它们的圆柱面近似和圆弧近似。以中国原子能科学研究院中微子质量测量β谱仪的磁场参数的依据。给出了一个宽9.6cm高10.0cm的大面积源算例,采用大面积源能使谱仪的亮度提高两个量级以上,而分辨却只加大一倍多点。理论计算结果与实验结果符合 的很好。     

^6LiF夹心谱仪探头用金硅面垒探测器性能测定

金硅面垒探测器是6LiF夹心谱仪探头的关键组成部分,其参数直接影响整个夹心谱仪的性能.通过实验测定了各金硅面垒探测器在不同偏压下的漏电电流、空气对α粒子的影响、金硅面垒的死层厚度、偏压对峰位和分辨率的影响,以及在180V偏压下各金硅面垒探测器的最大能量峰位.根据测量结果,选出了两组性能基本相同的金硅面垒探测器,将其组装成性能优良的6LiF夹心谱仪效应探头和本底探头.     

低温小立体角α谱仪的研制

研制了１套工作温度在室温至－２７．５℃、面源对探测器所张的相对立体角在５．２８７×１０－２—１．１１９×１０－４之间、分辨率达到１３．３ｋｅＶ的低温小立体角半导体α谱仪，研究了谱仪分辨率与探测器温度和相对立体角之间的关系。该谱仪已应用于α放射性比、α粒子能量、α粒子辐射几率和α放射性活度的测量。     

HPGe探测器的效率曲面研究

研究了高效率HPGe探测器测量近距离面源情况下的效率曲面。通过测量8种单能γ射线核素点源在探测器表面各点的相对效率及其面源效率,拟合得到了HPGe探测器的峰效率曲面和总效率曲面的解析表达式。使用该曲面计算的^60Co、^152Eu的真符合校正因子与实验测量结果基本一致。     

利用MCNP模拟气体裂变产物混合源的γ剂量率

西安脉冲反应堆辐照铀靶后,抽取Kr、Xe裂变气体,通过活性炭吸附于气体源盒内。HPGe γ谱仪测量源盒内混合气体活度,塑料闪烁探测器测量γ剂量率。将源盒、塑料闪烁探测器的几何结构、材料作为蒙特卡罗程序（MCNP）输入信息,模拟塑料闪烁探测器对源盒中核素活度与其γ剂量率对应关系,结合HPGe γ谱仪所测活度得到剂量率模拟值,结果与实测值偏差小于6%。该工作说明在已知放射源空间结构、放射性核素种类和活度的情况下,采用MCNP模拟计算复杂气体放射源γ剂量率的方法是可行的。     

NE230液体闪烁探测器对^24Naγ射线的响应

建立了NE230液体闪烁探测器γ射线谱仪,用该谱仪测量了^24Na源的γ射线,并将测量结果与NE213探测器的测量结果进行了比较。运用蒙特卡罗程序对实验所用探测器的γ射线进行了计算模拟,发现NE230实验结果与计算结果相差比较大。对探测效率及测量谱形的差异进行了探讨。     

Effect of Particle Recycling on Burn Control by Compression-Decompression

As a part of the development of a subcriticality monitoring system, a system which has a time series data acquisition function for detector signals and a real time evaluation function of the α value with the Feynman-α method was established, with which the kinetic parameter (α value) was measured at the STACY heterogeneous core. Hashimoto's difference filter was implemented in the system, enabling the measurement in a critical condition. The measurement result of the new system agreed with the pulsed neutron method. The α value was also evaluated by the newly developed algorithm of α-mode calculations for the Monte Carlo method, which was compared with the experimental value. Those computational and experimental α values show agreement within their uncertainties.     

Effect of environment humidity to radon measurement with SSNTD

moisture-absorbed film surface to α particles.Therefore, the calibration factor K should be corrected from the calculated result.     

Experimental analysis and uncertainty quantification using random sampling technique for ADS experiments at KUCA

Nuclear data-induced uncertainties of neutronics parameters (neutron multiplication factor k_eff, one-point kinetics parameters and prompt neutron decay constant α) are quantified for lead-bismuth zoned accelerator-driven system experiments at the Kyoto University Critical Assembly, in order to contribute validation for subcritical core analysis. The random sampling technique using SCALE6.2.1/Sampler/NEWT/PARTISN is utilized for the validation and the uncertainty quantification, because the random sampling technique is applicable for a problem which is not easy to apply the perturbation theory. Consequently, it is confirmed that the numerical results of α reasonably agree with the experimental ones, compared with the nuclear data-induced uncertainties. In addition, it is clarified that the nuclear data-induced correlations between α and k_eff and between α and neutron generation time Λ are strongly negative and positive, respectively. This fact implies that the numerical predictions of k_eff and Λ can be improved by the data assimilation technique using subcritical experimental results of α, which can be directly measured even for a deep subcritical system.     

反应堆动态参数的蒙特卡罗计算研究

介绍缓发中子有效份额(βeff)、有效中子代时间(Λeff)和本征值的概念及其蒙特卡罗程序计算方法。采用Prompt Method方法计算得到βeff;微扰法得到Λeff;采用瞬发中子密度衰减直接拟合法和间接求解法得到本征值;将各种反应性状态下的拟合得到临界c本征值,并与实验测量的c值进行比对,结果符合很好;并对动态参数蒙特卡罗程序计算的各种方法进行不确定度分析。     

BaF2探测器测量α粒子的时间分辨随温度变化实验研究

本工作对用于测量α粒子的BaF₂探测器的时间分辨随温度变化情况进行了实验研究。实验选用退激γ射线能量较高的²³⁷Npα源,利用α粒子与退激γ射线的时间关联性得到时间谱,在不改变任何条件的情况下对BaF₂晶体加热,加热到设定温度后保持恒温,在BaF₂晶体达到热平衡后开始测量时间谱,由该时间谱上读出的半高宽与标准偏差的线性关系得出α粒子的时间分辨随温度变化的情况。测量结果显示,时间分辨随温度变化在目前实验条件下较为明显,这为未来快时间分辨α粒子探测器的选择和优化使用提供了依据。     

GEM探测器α表面污染监测系统研制

研制了大面积GEM探测器,构建了位置灵敏α表面污染监测系统。该系统主要由GEM膜、多路读出电子学系统、数据获取与展示软件等组成。该系统对α粒子的本征探测效率可达95%以上,并实现了系统对α粒子的位置灵敏成像,可为表面污染类α粒子的精确位置测量提供一种有效手段。     

水中总α、总β放射性测量方法探究

利用低本底α、β测量仪研究影响水中总α、β放射性活度浓度测量的实验因素。通过一系列对比实验,获得样品放置时间、水样的贮存时间和贮存温度、样品制备方式等条件对实验结果的影响。结果表明:井水、自来水、地下水等水体内溶解的氡和红外线加热可能对水样残渣的计数产生干扰,样品制备完毕后,宜在室温且干燥环境下静置至少3小时后再进行上机测量;水样在密封贮存的情况下,贮存温度和时间对水样的总α、总β放射性活度无显著影响;采用现行国标推荐的硫酸酸化水样的方法可以有效避免样品可能存在的吸潮现象,减少实验误差。     

Study of the nuclide inventory of operational radioactive waste for the RBMK-1500 reactor

The experimental and modeling results on the radionuclide concentrations in the Ignalina NPP operational waste are presented in the work. The scaling factors between easy-to-measure γ emitters ¹³⁷Cs, ⁶⁰Co and a number of difficult-to-measure radionuclides, the activity measurements of which are related to radiochemical procedures, α and β spectrometry, have been determined. The study shows that the scaling factor method can be applied for RBMK-1500 reactor waste characterization. The scaling factors were used in determination of the nuclide composition of operational radioactive waste and characterization of radioactive waste during the Ignalina NPP decommissioning.     

Gamma ray absorption of cylindrical fissile material with dual shields

1 Introduction With the surging demand of nuclear energy from both military and civil industries, large quantities of nuclear fissile fuel, such as U and Pu, have been pro-duced and stockpiled. 235U and 239Pu, with the poten-tial risk of proliferation, have been the focal point of the international society. The International Atomic Energy Agency (IAEA) has been engaged in the nu-clear supervisory technology for many years. Since increased nuclear safeguards need more measurements, rapid m…     

Measuring energy loss of alpha particles in different vacuum conditions

In this paper,energy loss of alpha particles in different vacuum levels is studied experimentally and via theoretical analysis.A better understanding of energy loss of a particle in vacuum will help detect more exact numbers of alpha particles.Two ²³⁹Pu sources are used to measure the energy loss of a particle crossing different vacuum levels （different air pressures）.The experimental data are obtained from an instrument-PAM-100 developed by authors. The experimental results have shown that increasing vacuum levels will lead to more alpha residual energy but less energy loss.When the vacuum level reaches 0.04 MPa,alpha particles(²³⁹Pu,5.115 MeV)will lose the energy of about 0.175 MeV with traversing 5 mm distance.Theoretical calculations have shown a good agreement with experimental results.This implies that the instrument has a high accuracy and could be applied in field work.