150MeV质子入射固态金属靶性质研究

对150MeV质子入射钨、铅和铅－铋合金固态金属靶的性质进行了研究。就靶的几何设计、靶材料选择、150MeV质子入射靶中子产额和从靶中泄漏的中子产额、泄漏中子的能谱和空间分布、靶的放射性活度累积以及靶的辐射损伤进行了研究。     

可用一台ADS验证装置的150 MeV固态金属散裂中子靶的性质研究

对可以用于中国“加速器驱动洁净核能系统”的入射质子能量为150MeV,束流为3 mA的固态金属靶进行了研究。采用锥型几何结构作为靶的结构,材料选择钨,靶厚度为3 mm,对“靶-束窗”一体化结构进行了研究。研究了泄露中子产额和中子产额,泄露中子的能谱分布和空间分布,散裂碎片的分布以及能量沉积和辐射损伤。     

用不同程序模拟计算ADS散裂靶结果的比对(英文)

利用不同的程序对ADS散裂靶进行了模拟计算。用SNSP,SHIELD,DCM\CEM(Dubna Cascade Model\Cascade EvaporationMode)和LAHET等程序计算了长60 cm,直径20 cm的圆柱形铅靶,分别在800,1000,1500 and 2000 MeV的质子轰击下所产生的泄漏中子产额和能谱分布。模拟结果与实验数据进行了比较,对泄漏中子产额而言,SNSP模拟的结果与实验符合较好,SHIELD,DCM\CEM和LAHET计算的泄漏中子能谱分布比较一致。     

用LAHET和MCNP程序研究散裂中子靶的中子学性能

利用LAHET和MCNP程序对ADS散裂中子靶进行模拟计算。因靶的基本物理性质随束流和靶形状的变化而改变,所以首先评估了源强和靶的几何形状对靶性质的可能影响,然后计算长1.2m、直径为0.6m的圆柱形液态铅靶在1GeV质子轰击下,靶内中子的产生和泄漏及能量的沉积等。与文献数据、实验数据进行了比较,符合良好。计算结果还表明:源强和几何的选择对中子产生和泄漏可产生较大影响;用液态铅作散裂靶时,中子产额和泄漏额较高,且泄漏能谱在可利用范围内,但能量沉积在靶中的分布极不均匀,这可能给传热带来问题。     

加速器驱动的次临界系统散裂靶泄漏中子谱研究

为研究加速器驱动的次临界系统（ADS）散裂靶的散裂中子学特性,采用Geant4计算不同能量质子轰击铅铋靶产生的泄漏中子产额、能谱、轴向积分分布。模拟得到1 GeV质子对应的靶的优化尺寸及优化后泄漏中子谱,计算结果可为ADS散裂靶件和堆芯设计提供参考。     

用于中子测井的自成靶密封中子管性能评价

采用自成靶工艺,研制了SNT-DT/25型密封氘氚中子管,对其工作温度、使用寿命、功耗、中子产额及其稳定性等性能参数进行了测试。结果表明:中子管使用温度可达175℃,最高中子产额≥1×109 n/s,中子产额浮动≤10%;在靶极电压-80kV、阳极电流300μA、靶流80μA的工作条件下,中子产额可达1×108 n/s,中子管的性能指标完全满足中子测井使用要求。此外,本文还对中子产额随靶极电压、阳极电流的影响进行了分析。     

密封中子管氘-氘产额及二次电子抑制

中子管的工作参数是影响中子产额的重要因素.为了更准确地调控D-D中子管的中子产额,对中子管的工作参数与产额关系进行了研究,同时为了提高中子管束流品质及寿命,对中子管的二次电子抑制进行实验.采用控制参数变量的方法分别研究了D-D中子管的热子电流、阳极高压、靶极高压对中子产额的影响,以及二次电子抑制电阻阻值与靶极电流之间的...     

离子源及厚靶参数对氘氚反应中子源中子产额的影响

用厚靶氘氚(D-T)反应中子产额的计算方法模拟计算了入射氘离子能量为120 keV时D-T中子源的中子产额。研究了氘离子源产生的束流中单原子氘离子(D+)及双原子氘离子(D2+)比例对中子产额的影响。结果表明,提高D+比例,同时降低D2+比例将有效提高中子产额。另外还研究了不同靶膜材料及组分引起的中子产额变化。表明中子产额与靶膜中氚的含量成正比,与靶膜元素的原子质量成反比。同时分析讨论了离子源品质及靶参数对中子源整体性能的影响,得出离子源束流品质的提高对中子源整体的设计至关重要。最后,模拟计算了靶膜表面有氧化层情况下中子产额的变化,并与实验结果作了对比。在此基础上提出了一种新的靶设计方案,并对其物理可行性进行了研究。     

厚铍靶9Be(d,n)反应中子产额测量

能量在3MeV以下厚靶D-Be反应的中子产额实验数据至关重要,但较为缺乏。本工作在北京大学4.5MV静电加速器上对氘束轰击厚铍靶的中子产额进行测量。对入射氘核能量在0.35~2MeV之间的若干能量点用长中子计数管进行了0°方向中子产额、中子角分布及中子总产额的测量。与已有的测量结果和经验公式进行了比较,并拟合出氘束轰击厚铍靶中子总产额的经验公式。     

44GeV或18GeV ^12C离子轰击Cu靶或Pb靶时中子产额的研究

用ＣＲ－３９迭层探测器测量了４４ＧｅＶ或１８ＧｅＶ１２Ｃ离子轰击Ｃｕ靶或Ｐｂ靶时中子产额与入射粒子能量以及靶核质量的关系。当入射能量由１８ＧｅＶ增至４４ＧｅＶ时，Ｃｕ靶的中子产额增大２．１２±０．１９倍，Ｐｂ靶的中子产额增大２．０４±０．１５倍。Ｐｂ靶和Ｃｕ靶中子产额之比在４４ＧｅＶ和１８ＧｅＶ分别为２．５４±０．２０和２．５６±０．２０。     

AB-BNCT中子靶物理设计分析

质子加速器适用于为硼中子俘获治疗提供中子源,其中子源强及能谱较反应堆中子源更具可调性。中子靶物理计算分析是加速器中子源设计的基础,为其提供粒子能量、流强等参数需求分析,并为靶体结构尺寸设计、中子慢化和屏蔽分析等提供前端参数。本文利用MCNPX蒙特卡罗程序,通过对质子打靶的中子产额和能谱、靶体能量沉积、打靶后靶材放射性活度和中子出射空间角分布等进行研究,提出能量2.5 MeV质子轰击100～200 μm锂靶的设计,并用模拟计算数据论证其合理性。该设计中子源在1 mA流强质子轰击下,源强可达9.74×10¹¹ s^-1;拟设计15 mA、2.5 MeV质子束产生的中子源,在治疗过程中靶材放射性活度累积最大值约为1.44×10¹³ Bq。     

ADS熔盐散裂靶中子学性能研究

与传统加速器驱动次临界系统（ADS）采用金属靶作为散裂中子靶的设计不同,加速器驱动次临界熔盐堆（AD-MSRs）采用靶堆一体的设计,直接使用燃料熔盐作为散裂中子靶。由于熔盐靶的中子学性能直接影响AD MSRs的能量放大系数、核废物的嬗变和核燃料增殖的效率,所以本研究基于MCNPX程序,详细计算了高能质子轰击氟盐和氯盐两种熔盐靶产生的散裂中子产额、散裂中子能谱、能量沉积分布以及散裂产物等中子学性能,并与液态Pb和铅铋共熔体（LBE）两种液态金属靶进行了对比。计算结果表明,熔盐靶在散裂中子产额上与液态金属靶有一定的差距,但熔盐靶内能量沉积分布的梯度较小,更有利于靶区的热量导出。与液态Pb和LBE靶相比,熔盐靶的散裂产物中包含更多的气体以及高质量数的α发射体核素。     

Heavy particle range and energy deposition distributions in solids

The transport equations describing incident ion locations as they slow to a stop in a solid target have been derived and solved in the approximation of a Gaussian distribution. These distributions have then been used to determine the local rate at which energy is deposited into structural damage and ionization by both the incident ion and the recoiling target atoms. Incident particle and energy deposition distributions are readily and easily obtained through this method for both simple and compound targets, including in particular those alloys and compounds of direct interest in CTR studies. The calculated final particle distributions have been found to agree well with experiment and the calculated damage energy distributions correlate well with measured distributions of simple and complex defects. The results of such calculations provide the first step in understanding the details of individual 14 MeV neutron damage clusters.     

Considerations for a cold moderator on a pulsed neutron source

The purpose of a cooled moderator on a pulsed neutron source may be to extend to longer wavelengths the neutron slowing down range with its narrow pulse widths, or to enhance the long wavelength intensity. The intensity and pulse length as a function of wavelength are determined by the rate of energy exchange, and by leakage and capture of neutrons. Energy deposition and radiation damage present serious problems, and restrict the choice of moderators. Radiation damage, in particular, may limit the lifetime and stability of the moderator, giving rise to problems of corrosion and, in the case of solid moderators, stored energy release. The advantages of solid ammonia are its high hydrogen atom density, and its thermal neutron absorption cross-section which allows the moderator to act as its own homogeneous poison. On the other hand this impairs its use for cold neutron production in those instances where neutron intensity rather than burst width is important. In such cases solid methane is favourable, though the radiation damage problem for methane at high intensity sources is severe, and liquid hydrogen is indicated.     

An innovative target for the RACE HP experiment

In the RACE (reactor-accelerator coupling experiments) project, a series of ADS (accelerator driven system) experiments are envisaged for the study of the coupling of a neutron source with sub-critical reactors. In these experiments, a continuous electron beam impacts on an actively cooled solid target where it is converted through photonuclear reactions in a neutron flux, able to feed the reactor. In a RACE foreseen ‘high power’ phase, where the beam power would be enhanced from 1 to about 30 kW, the target would be submitted to very severe conditions both from the mechanical and the thermal points of view. In this paper, the development of a new concept of uranium target is described with detailed neutron production analyses, power deposition distributions, thermo-mechanical simulations and cooling schemes. Two possible solutions are envisaged in order to control the power deposition distribution.     

铅散裂中子靶物理特性研究

利用蒙卡程序DCM/CEM对ADS标准散裂中子靶进行了计算。计算了长0.6 m,直径0.2 m的圆柱形208Pb靶,在0.1～1.6 GeV的质子轰击下,Pb靶发生散裂反应产生的中子产额及表面的中子注量、能谱分布以及靶内能量沉积分布,解释了以前的实验结果。计算结果与文献数据、实验数据进行了比较,符合良好,对进一步进行ADS堆芯设计具有较好的理论指导意义。     

Preliminary physics study of the Lead–Bismuth Eutectic spallation target for China Initiative Accelerator-Driven System

The Lead-Bismuth Eutectic(LBE) spallation target has been considered as one of the two alternatives for the spallation target for China Initiative Accelerator-Driven System.This paper reports the preliminary study on physical feasibility of a U-type LBE target with window.The simulation results based on Monte Carlo transport code MCNPX indicate that the spallation neutron yield is about 2.5 per proton.The maximum spallation neutron flux is observed at about 3 cm below the lowest part of the window.When the LBE target is coupled with the reactor,the reactor neutrons from the fission reaction increased the neutron field significantly.The energy deposition of highenergy protons is the main heat source;the spallation neutrons and reactor neutrons contribute only a small fraction.The maximum energy deposition in the LBE is about 590 W/cm~3 and that in the target window is about319 W/cm~3.To estimate the lifetime of the target window,we have calculated the radiation damages.The maximum displacement production rate in the target window is about10 dpa/FPY.The hydrogen and helium production rates generated during normal operation were also evaluated.By analyzing the residual nucleus in the target during the steady operation,we estimated the accumulated quantities of the extreme radioactivity toxicant ~(210)Po in the LBE target loop.The results would be helpful for the evaluation of the target behavior and will be beneficial to the optimization of the target design work of the experimental facilities.