线缆X射线瞬态响应的电路模型计算

建立了同轴电缆和腔体内带保护层导线、裸导线X射线瞬态辐照响应的电路计算模型,该模型考虑了X射线辐照线缆时电子的运动规律及瞬态响应的产生机理,适用于瞬态响应的规律研究和工程预估。结合实例,介绍了计算模型中电流源、电容参数的物理意义及其计算方法,采用该模型计算了同轴屏蔽电缆的X射线瞬态响应,并与数值计算结果进行了比较。结果表明,电容的计算是采用电路模型计算响应的关键,采用衰减法计算的电子射程更适合计算电容。     

不同能量光子辐照电缆响应规律研究

利用时域传输线(TL)方法计算了不同能量光子辐照同轴屏蔽电缆时的响应规律。计算结果表明：光子能量不同时,电缆介质层中沉积电荷分布不同导致电缆响应极性发生了变化;光子能量增大到一定值后,响应变化幅度很小;1MeV的单能电子经钽靶发生韧致辐射后在电缆上的瞬态辐照响应是前向电子和光子在电缆上响应的综合,两者在电缆上的电压响应均为负值,幅度差别在1.8倍以内;钽靶后面增加一定厚度的铝材料,可明显减小前向电子在电缆响应中的比例。     

基于实验数据的吊篮表面脉动压力分析

基于堆内构件缩比模型流致振动实验实测得到的吊篮表面脉动压力数据,分析了吊篮表面不同位置脉动压力功率谱密度的分布特征,并对脉动压力功率谱密度的相关性进行分析得到相关长度的特性。结果表明,吊篮表面的脉动压力功率谱密度随频率的增大快速减小然后趋于平缓,是一种频率成份十分丰富的宽带衰减谱,在吊篮同一高度区域的脉动压力功率谱密度基本相同,不同高度区域的脉动压力功率谱密度的能量差别较大;脉动压力功率谱密度的相关长度随频率递增而急剧减小然后趋于常值;吊篮流致振动响应对脉动压力功率谱密度的影响较小,将吊篮流致振动简化为弱耦合问题是合理的。      

塑料闪烁光纤在γ光子下的康普顿能谱能量分辨率模拟分析

利用Geant4软件模拟了塑料闪烁光纤在中能γ光子(0.8–6 MeV)入射情况下的康普顿能谱,讨论了能量分辨率与半径的变化关系,分析了γ光子在闪烁光纤间串扰对能量分辨率的影响。结果表明,选择合适的光纤半径,能得到较好的康普顿能谱效应,半径为15–35 mm时,最佳的能量分辨率可达8.7%。     

严重事故下吸湿性气溶胶的自然去除研究

反应堆发生严重事故时,堆芯释放出的吸湿性气溶胶会在潮湿的安全壳内增大,从而影响其自然去除过程。本文理论推导了吸湿性气溶胶的增大模型并通过多种方法对其进行了验证。模型计算结果表明,气溶胶的增大过程由于受到溶解度的限制而存在临界湿度值,在该临界值以下时气溶胶不发生吸湿,但这未被其他严重事故分析程序所考虑。同时,基于某三代先进压水堆的特定严重事故工况,本文分析了干颗粒半径及湿度对气溶胶的平衡半径和自然去除系数的影响。结果表明:气溶胶的自然去除系数随干颗粒半径的增大将先减小后增加,并在1μm时达到最小值;相同湿度下,干颗粒半径对气溶胶半径的最大增大比例的影响不大;湿度的增加对不同干颗粒半径气溶胶去除系数的影响不同。     

液态熔盐堆堆芯功率模糊PID控制

液态熔盐堆采用熔融氟化盐为燃料,燃料熔盐出口温度是衡量熔盐堆安全的重要指标。通过堆芯功率控制可实现燃料熔盐出口温度控制。将液态熔盐堆堆芯划分成内区和外区,并基于能量守恒原理建立堆芯非线性模型,采用微扰理论对非线性模型进行线性化。基于堆芯线性化模型,采用模糊比例-积分-微分(PID)控制器设计堆芯功率控制系统。以熔盐增殖堆(MSBR)为例,开展堆芯功率控制仿真。结果表明,引入10^-3、2×10^-3阶跃反应性时,模糊PID控制器可以减小系统响应的上冲幅度和超调量,并且在堆芯功率发生了较大的负荷变化时,模糊PID控制器可以对堆芯功率的变化实现良好跟踪。故所采用的模糊PID控制器具有良好的动态性能,可实现对堆芯功率的良好控制。     

电子束与复合靶作用后辐射特性的数值模拟

建立了复合靶的蒙特卡罗粒子输运计算模型,以“闪光二号”加速器为电子束源,模拟了电子和光子在不同材料中的输运规律,研究了钽和聚乙烯组成的复合阳极靶对辐射X射线场的影响。模拟结果表明：随着钽厚度的增加,辐射X射线平均能量增大,能量转换效率先增大后减小;聚乙烯可明显减小辐射场中的电子份额。当钽和聚乙烯的厚度分别取20 μm、3 mm时,辐射场中平均光子能量为102.68 keV;光子总能量为88.62 J,远大于电子总能量0.02 J;X射线能量转换效率为0.57%。根据数值模拟结果和实验条件设计了复合靶,计算和测得的X射线平均能量分别为108和121 keV,二者符合得较好。     

双铅铋回路自然循环瞬态响应分析

为了研究液态金属双自然循环回路功率变化时的瞬态响应和回路的稳定性,利用SIMULINK在单个铅铋自然循环回路的基础上建立了双自然循环回路模型,并用FLUENT程序进行计算验证,分析了不同升功率和降功率过程中回路的流速振荡及双回路的稳定性。计算结果表明:延长升功率时间可减小流速振荡,且当升功率速率先慢后快时更有利于减小流速振荡和缩短流动到达稳定所需的时间;对于双自然循环回路,当降功率速率不同时,回路的流速均未发生明显的振荡,降功率速率对回路的稳定性影响并不显著。双自然循环回路比单回路更不稳定,通过减小中间换热面的热阻能有效提高双回路的稳定性。     

裂变气体气泡尺寸对弥散燃料颗粒内部特征的影响规律

在前期均匀裂变气体气泡尺寸弥散燃料颗粒开裂模型基础上,基于不同尺寸气泡压力作用于燃料相的米塞斯(Mises)应力相等这一假设条件,建立了非均匀气泡尺寸的燃料颗粒开裂模型,并通过模型计算了裂变气体气泡尺寸对燃料相等效层厚度、气泡中气体原子数、气泡压力、燃料相最大张应力等内部特征的影响规律。计算结果表明:当气泡半径较大时,燃料相等效层厚度与气泡半径近似呈线性关系,当气泡尺寸较小时,等效层厚度与气泡半径之比随气泡半径减小急剧增加;随着气泡半径减小,气体原子数浓度增加;在升温过程中气泡内壁最大张应力的增大速率明显高于开裂阻力,气泡半径越小,燃料颗粒开裂温度越低。     

基于MCNP对γ辐射积累因子不同影响因素的研究

通过蒙特卡罗程序来模拟计算γ辐射积累因子,以找出不同条件下积累因子受各因素的影响,为屏蔽研究提供一定的数据参考。就γ辐射积累因子的影响因素:γ光子能量,源的几何尺寸,辐射角和屏蔽层厚度,通过MCNP程序进行了模拟计算。初步结论为:轻元素和中等元素构成的介质在厚度一定的情况下,积累因子随着γ光子初始能量的减小而增大;相对于轻材料,重材料的积累因子较小;随着源的线度增大而增大;随着准直角进一步增大而增大,源的各向同性程度增高会导致积累因子增加;随着源与探测器之间介质厚度的增加,积累因子增大,对于高能辐射源和具有中偏低原子序数Z的元素,积累因子增长速率接近于线性。     

Primarily Experimental Results for a W Wire Array Z Pinch

Primarily experimental results are given for a W wire array Z pinch imploded with up to 2 MA in 100 ns on a Qiangguang-I pulsed power generator. The configuration and parameters of the generator, the W wire array load assembly and the diagnostic system for the experiment are described. The total X-ray energy has been obtained with a averaged power of X-ray radiation of 1.28 TW.     

Expansion of Plasma of Electrically Exploding Single Copper Wire Under 4.5kA～9.5kA/Wire

Abstract The experimental system for electrically exploding single metal wire has been de-signed and manufactured. Expansion of the dense plasma column formed from an electricallyexploding Cu wire of diameter 30 μm has been studied with a high-speed photographer to obtainthe time-dependent radius (R-t) curve. The experimental results demonstrate that the mean ex-pansion rate of the dense plasma column is 1.94 μm/ns, 2.6 μm/ns and 3.75 μm/ns according tothe peak pulse current 4.5 kA, 7 kA and 9.5 kA respectively. The results can be beneficial to givinga profound understanding of the early stage of wire-array Z-pinch physics and to improvement ontheir design.     

电缆屏蔽效能评估方法比较研究

针对核电磁脉冲,提出了具有工程实际应用价值的峰值屏蔽效能评估指标和脉冲时域测量系统;测试了某型镀银编织屏蔽电缆的转移阻抗,利用Kely理论模型与频域试验验证了测试数据的有效性,三者对比分析结论一致,效果良好。     

直流X射线模拟电缆X射线响应的可行性

本文对电缆X射线辐照响应的机理和模拟方法进行了研究,分析了电缆直流和脉冲X射线辐照响应的异同。建立了带状电缆X射线辐照响应一维计算模型,该模型包含电缆屏蔽层和介质层间隙、介质层瞬态辐射感应电导率等计算模型,模拟了带状电缆直流和脉冲X射线辐照电流响应。模拟结果表明,在X射线注量相同的条件下,电缆直流和方波脉冲X射线响应具有类似的波形特征及相同的间隙电压。因此,在该计算模型描述的电缆X射线辐照响应机制下,可利用直流X射线开展相应的脉冲X射线辐照响应机制模拟。     

自给能中子探测器关键材料及元件的研制进展

本文介绍了我国在运核电机组的基本状况以及国内核电自给能中子探测器的发展形势.详细分析了自给能中子探测器的结构特点、原理和应用,以及三代核电技术堆内核测系统的需求和使用寿命.阐述了自给能中子探测器用关键材料的国内外研制进展,重点分析了钒丝、铑丝和铠装信号电缆的制备工艺难点以及性能要求,阐明了钒丝、铑丝的高纯化与微量元素控...     

Discharge electrode configuration effects on the performance of a plasma sparker

A multi-electrode array is commonly applied in a plasma sparker to generate stable acoustic pulses.In this paper,the effects of the electrode configuration on the performance of a plasma sparker have been investigated.In terms of the load electrical characteristics,the electrode radius and distance have negligible influence on the electric characteristics,whereas a larger electrode number results in a smaller voltage and a larger current but has little effect on the load energy.Regarding the acoustic characteristics,both the expansion and collapse pulses can be increased by decreasing the electrode tip radius.the influence of the electrode number and electrode gap distance on the amplitude of the expansion pulse was found to be negligible.And the amplitude of the collapse pulse decreases significantly with increasing electrode number.Increasing the electrode number decreases the energy efficiency for intense bubble interactions,thus,a small electrode tip radius and a small electrode number are preferred for the design of a plasma sparker if the total discharge energy is given.     

Discharge and post-explosion behaviors of electrical explosion of conductors from a single wire to planar wire array

This work deals with an experimental study of a Cu planar wire array (PWA) in air and water under the stored energy 300–1200 J. A single Cu wire is adopted as a controlled trial. Four configurations of PWA and a wire with the same mass (cross-section area) but the different specific surface areas (15–223 cm² g⁻¹) are exploded. The transient process is analyzed using high-speed photography in combination with the results of optical emission and discharge. Discharge characteristics revealed that PWA always has a higher electric power peak, early but higher voltage peak, as well as faster vaporization and ionization process than the single-wire case. Two to three times stronger optical emission could be obtained when replacing the single-wire with PWA, indicating a higher energy-density state is reached. Phenomenologically, in both air and water, single-wire load tends to develop a transverse stratified structure, while PWA is dominated by the uneven energy deposition among wires. Finally, the synchronism and uniformity of the PWA explosion are discussed.     

Radiation Induced Currents in Subminiature Coaxial Cables

Subminiature coaxial cables smaller than RG-58 were exposed to intense pulsed irradiation from a plasma focus device, and the currents induced on the center conductors were measured in a vacuum environment. The incident photons had energies mostly below 70 keV, and filters were used to vary the average hardness of the irradiation. The measured cable responses in units of Coulomb/rad(Si)-cm were compared to values calculated on the basis of photoemission from metal surfaces and electron ranges in insulators. It was found that the currents induced on the center conductors were several times larger than predicted for an ideal coaxial geometry because of small gaps between the dielectric surface and overlapping braid wires. For a given cable type, such as RG-174/U, large variations in cable responses were found according to each manufacturer's construction techniques.