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。     

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。     

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。     

加速器驱动的次临界系统散裂靶热工水力研究

散裂靶位于加速器驱动的次临界系统（ADS）的中心,为核嬗变提供所需的中子源。通过分析散裂靶的热工要求,选取铅铋合金（LBE）作为ADS的靶材料和冷却剂。使用MCNP程序计算质子束轰击靶区产生的能量沉积,并使用CFD程序FLUENT计算靶区热工特性。分析了不同设计参数及不同靶窗形状对ADS靶区温度分布和速度分布的影响,得到满足热工要求的可选方案。     

用DCE/CEM和LAHET软件计算ADS标准散裂靶的比较

利用蒙卡程序DCM／CEM和LAHET对加速器驱动的次临界系统ADS标准散裂中子靶进行了计算。长为0．6m、直径为0．2m的圆柱形^208Pb靶在0．15—1．6GeV的高能质子轰击的情况下,利用两软件对质子在靶内的能量沉积、Pb靶发生散裂反应产生的中子及靶内和表面的中子注量、中子能谱分布等进行了比较计算。结果表明：两者模拟结果在中能区(0．8—1．0GeV)符合很好,但在质子能量较高或较低时,两者略有差别。     

加速器驱动次临界系统的中高能质子轰击厚靶中子学实验研究

利用俄罗斯杜布纳联合核子研究所的高能加速器进行加速器驱动次临界系统 (ADS)靶区中子学研究。用 0 .5 33、1 .0、3.7和 7 4GeV质子轰击U(Pb)、Pb和Hg靶的测量结果表明 :U(Pb)和Pb与Hg靶的中子产额比分别为 ( 2 0 1± 0 1 0 )和 ( 1 76± 0 33) ,从获得较强中子的角度看 ,Hg作为ADS靶是不利的 ;沿厚 2 0cm靶的中子产额随入射质子穿透深度增大而下降 ,质子能量越低 ,中子产额下降越快 ,为在较大厚度范围内获得较均匀的中子场 ,质子能量不应低于 1GeV ;不同能量质子产生的次级中子能谱相近 ,但随质子能量提高 ,较高能量中子的比例逐渐增大。     

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。     

ADS中液态铅铋靶流动管道屏蔽计算

对于具有独立回路冷却液态铅铋(Liquid Lead-bismuth Eutectic,LBE)散裂靶的加速器驱动的次临界系统(Accelerator Driven Sub-critical System,ADS),高能质子束流辐照靶体产生的散裂产物进入管道后,会持续释放光子,会对靠近流动管道的工作人员造成辐射损伤。本文利用高能粒子输运程序Fluka计算散裂靶的散裂产物累积产额,然后利用放射性衰变计算程序Origen2计算散裂产物释放的光子强度及分群能谱,最后利用Fluka进行流动管道内光子源项的屏蔽计算。对一种典型的Y型LBE有窗靶进行的流动管道屏蔽计算结果表明,参照GB18871-2002职业性放射性工作人员年剂量当量限值20 m Sv的标准,若使用铅作为屏蔽材料,流动管道的管壁应该加厚20 cm。本文工作可为ADS系统LBE有窗靶的回路屏蔽设计提供参考。     

ADS散裂靶产生的放射性毒性

利用SHIELD程序计算不同能量质子照射不同靶产生的散裂产物分布。采用年摄入量限值(ALI)标准定义的放射性毒性，对散裂靶中散裂产物产生的放射性毒性进行研究分析。研究结果表明：散裂产物具有较大的毒性，特别是在加速器驱动的次临界系统(ADS)要求的入射粒子(质子)能量下，产生了一些处于稀土区长寿命的α放射性核素。这些核素若不能在辐射场中被嬗变掉，其毒性将对生物环境产生长期的影响。     

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。     

Implementation of an LBE spallation target in an accelerator-driven molten salt subcritical reactor

An accelerator-driven system (ADS) combined with a subcritical molten salt reactor (MSR) is a type of hybrid reactor originally designed to use Th/U (or U/Pu ) fuel cycles. In most accelerator-driven molten salt reactor (AD-MSR) concepts, the salt material is also used as a target for inducing spallation neutrons. Although a neutron source is an important component in the design of ADS, only a few studies have addressed the effects of the neutron spallation source in the AD-MSR. Incidentally, there is no quantitative study on how much the beam power can be reduced by installing a spallation target in a sodium chloride-based fast reactor. We studied the proton and the neutron source efficiencies of an AD-MSR with chloride fuels by considering an Lead Bismuth Eutectic (LBE) spallation target. This LBE target is found to increase the proton source efficiency significantly. The required beam power for an AD-MSR can be reduced by 33 % and 16 % for NaCl-Th/²³³U and NaCl-U/Pu fuels, respectively, relative to the AD-MSR without the LBE spallation target by keeping the same k_eff. The energy gain can be increased up to 1.5 times and 1.2 times for NaCl-Th/²³³U and NaCl-U/Pu fuels, respectively. Thus, incorporating a spallation target module in an AD-MSR can significantly reduce the burden on the accelerator.     

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.     

150 MeV加速器驱动的反应堆系统固态金属靶优化研究

对150MeV加速器驱动的反应堆系统的固态靶进行了优化，就靶的几何设计、靶中泄漏中子产额、泄漏中子能谱及靶中能量沉积问题进行了研究。提出了钨饼与水组成的组合靶的概念，在中子产额影响较小的情况下，较好地解决了固态靶散热问题。     

Preparation and verification of mixed high-energy neutron crosssection library for ADS

An accelerator-driven subcritical system(ADS)is driven by an external spallation neutron source, which is generated from a heavy metal spallation target to maintain stable operation of the subcritical core, where the energy of the spallation neutrons can reach several hundred megaelectron volts. However, the upper neutron energy limit of nuclear cross-section databases, which are widely used in critical reactor physics calculations, is generally 20 MeV.This is not suitable for simulating the transport of highenergy spallation neutrons in the ADS. We combine the Japanese JENDL-4.0/HE high-energy evaluation database and the ADS-HE and ADS 2.0 libraries from the International Atomic Energy Agency and process all the data files for nuclides with energies greater than 20 MeV. We use the continuous pointwise cross-section program NJOY2016 to generate the ACE-formatted cross-section data library IMPC-ADS at multiple temperature points. Using the IMPC-ADS library, we calculate 10 critical benchmarks of the International Criticality Safety Benchmark Evaluation Project manual, the 14-MeV fixed-source problem of the Godiva sphere, and the neutron flux of the ADS subcritical core by MCNPX. To verify the correctness of the IMPCADS, the results were compared with those calculated using the ENDF/B-VII.0 library. The results showed thatthe IMPC-ADS is reliable in effective multiplication factor and neutron flux calculations, and it can be applied to physical analysis of the ADS subcritical reactor core.     

Influence of geometrical and material parameters on flow rate in simplified ADS dense granular-flow target: a preliminary study

The spallation target is one of the key components of an accelerator-driven subcritical system (ADS). Following previous designs such as plate targets, rod targets, rotating targets, and liquid metal targets, the gravity-driven dense granular-flow target (DGT), which combines the advantages of solid and liquid metal targets, becomes a new attractive choice. The geometry of DGT consists of a cylindrical hopper and an internal coaxial cylindrical beam pipe. In this paper, using discrete element method simulations on graphics processing units, we research into the relations of the flow rate with the geometrical as well as the material parameters. For geometrical parameters, it is found that the existence of an internal pipe does not influence the flow rate when the distance from the bottom of the pipe to orifice is large enough. The results also reveal how the material parameters influence the flow rate. The whole research is helpful for the design of DGT.     

AFM and MFM characterization of oxide layers grown on stainless steels in lead bismuth eutectic

Fast reactors and spallation neutron sources may use lead bismuth eutectic (LBE) as a coolant. Its thermal physical and neutronic properties make it a high performance nuclear coolant and spallation target. The main disadvantage of LBE is that it is corrosive to most steels and container materials. Active control of oxygen in LBE will allow the growth of protective oxides on steels to mitigate corrosion. To understand corrosion and oxidation of candidate materials in this environment and to establish a solid scientific basis the surface structure, composition, and properties should be investigated carefully at the smallest scale. Atomic force microscopy (AFM) is a powerful tool to map out properties and structure on surfaces of virtually any material. This paper is a summary of the results from AFM measurements on ferritic/martensitic (HT-9) and austenitic (D9) steels that are candidates for liquid metal cooled reactors.     

Burn-up characteristics of ADS system utilizing the fuel composition from MOX PWRs spent fuel

Burn-up characteristics of accelerator-driven system, ADS has been evaluated utilizing the fuel composition from MOX PWRs spent fuel. The system consists of a high intensity proton beam accelerator, spallation target, and sub-critical reactor core. The liquid lead–bismuth, Pb–Bi, as spallation target, was put in the center of the core region. The general approach was conducted throughout the nitride fuel that allows the utilities to choose the strategy for destroying or minimizing the most dangerous high level wastes in a fast neutron spectrum. The fuel introduced surrounding the target region was the same with the composition of MOX from 33 GWd/t PWRs spent-fuel with 5 year cooling and has been compared with the fuel composition from 45 and 60 GWd/t PWRs spent-fuel with the same cooling time. The basic characteristics of the system such as burn-up reactivity swing, power density, neutron fluxes distribution, and nuclides densities were obtained from the results of the neutronics and burn-up analyses using ATRAS computer code of the Japan Atomic Energy research Institute, JAERI.     

Accelerator-driven system for transmutation of high-level waste

The accelerator-driven transmutation system has been studied at the Japan Atomic Energy Research Institute. This system is a hydrid system which consists of a high intensity accelerator, a spallation target and a subcritical core region. In the conceptual design study, two types of system concepts, sodium cooled and lead-bismuth cooled system, are being studied. In this study, we fucus on our lead-bismuth cooled accelerator-driven transmutation system to investigate basic characteristics. The fuel compositions were optimized for efficient transmutation of minor actinide. The transmutation of long-lived fission products was also considered.     

Design study of lead-bismuth cooled ADS dedicated to nuclear waste transmutation

Research and development on nuclear waste transmutation are being carried out with a special emphasis placed on dedicated accelerator-driven systems at the Japan Atomic Energy Research Institute under the Japanese OMEGA Program. The reference accelerator-driven system design employs eutectic lead-bismuth as spallation target material and coolant. The fuel for the subcritical core is minor-actinide mononitride. The system consists of a 1.5GeV, 14mA proton accelerator and an 800MWt subcritical core with an effective neutron multiplication factor of 0.95. The transmutation rate of minor actinides is approximately 250 kg/y at 80% load factor. The design has salient features that the coolant inventory is large due to the tank-type configuration, the temperature rise through the core is relatively low, and the power conversion is operated on a saturated steam turbine cycle. These features make the plant response to a beam trip slow and much less demanding.     

Investigation of Lead Target Nuclei Used on Accelerator-Driven Systems for Tritium Production

High-current proton accelerators are being researched at Los Alamos National Laboratory and other laboratories for accelerator production of tritium, transmuting long-lived radioactive waste into shorter-lived products, converting excess plutonium, and producing energy. These technologies make use of spallation neutrons produced in (p,xn) and (n,xn) nuclear reactions on high-Z targets. Through (p,xn) and (n,xn) nuclear reactions, neutrons are produced and are moderated by heavy water. These moderated neutrons are subsequently captured on ³He to produce tritium via the (n,p) reaction. Tritium self-sufficiency must be maintained for a commercial fusion power plant. Rubbia succeeded in a proposal of a full scale demonstration plant of the Energy Amplifier. This plant is to be known the accelerator-driven system (ADS). The ADS can be used for production of neutrons in spallation neutron source and they can act as an intense neutron source in accelerator-driven subcritical reactors, capable of incinerating nuclear waste and of producing energy. Thorium and Uranium are nuclear fuels and Lead, Bismuth, Tungsten are the target nuclei in these reactor systems. The spallation targets can be Pb, Bi, W, etc. isotopes and these target material can be liquid or solid. Naturally Lead includes the ²⁰⁴Pb (%1.42), ²⁰⁶Pb (%24.1), ²⁰⁷Pb (%22.1) and ²⁰⁸Pb (%52.3) isotopes. The design of ADS systems and also a fusion-fission hybrid reactor systems require the knowledge of a wide range of better data. In this study, by using Hartree–Fock method with an effective nucleon-nucleon Skyrme interactions rms nuclear charge radii, rms nuclear mass radii, rms nuclear proton, neutron radii and neutron skin thickness were calculated for the ^{204, 206, 208}Pb isotopes. The calculated results have been compared with those of the compiled experimental and theoretical values of other studies.