中国散裂中子源氢循环系统的氢排放方案设计

为保障中国散裂中子源(CSNS)氢循环系统停机时,顺利、安全地将低温氢排放至大气中,设计一套可靠的氢排放系统非常重要。设计的氢排放系统包括氢排放管道、氢放空管、净化吹扫管道以及排放控制阀、阻火器、止回阀等装置。介绍了CSNS氢循环系统流程,CSNS氢排放方式和氢排放系统的流程,详细阐述了氢排放管道的设计和允许排放流量的计算。CSNS氢排放系统的设计考虑了CSNS装置的现场环境、风向、风速及居民区的距离,并通过计算确定了氢排放管道的长度,氢排放的最小流量和最大流量。     

散裂中子源低温系统的概念设计

为促进中子散射技术在中国的进一步发展,中国科学院和广东省政府将在广东省东莞市建设一座基于加速器的散裂中子源装置(CSNS).设计的低温系统主要包括氦制冷机、氢循环冷箱和氢安全系统,其中氢循环系统采用单相超临界氢循环工质,氢泵强制循环的技术模式.氦制冷系统提供低温氦气,通过换热器将氢循环回路的全部热负荷带走,氢安全系统采用了多重屏障隔绝措施来确保低温系统的安全.介绍了CSNs低温系统的基本原理和布局,并详细说明了其主要技术参数及工作过程.     

中国散裂中子源低温系统的氢降温优化研究

为了保障中国散裂中子源(CSNS)低温系统的平稳、顺利降温,减小降温过程中的压力波动,避免放气造成冷源的损失和温度的反复,研究了低温系统近两年多轮降温实验的降温曲线和数据,逐渐优化了氢降温控制逻辑.通过制冷机控制软件的升级和控制逻辑的修改,实现了300-34K的平稳降温,使降温过程由完全不可控提升到了半可控阶段.通过3...     

中国散裂中子源小型非直冷式低温恒温器技术

中国散裂中子源(CSNS)中国自主建设的第一台散裂中子源,CSNS一期工程需设计并配置3套以上的小型低温恒温器。介绍了CSNS小型非直冷式低温恒温器及系统设计、系统控制设计以及测试结果,获得了该恒温器内真空腔的真空度、样品管氦气压力与温度之间的变化关系,为低温恒温器的设计和在CSNS应用中的运行维护提供了理论依据。     

散裂中子源超临界低温氢循环用氢氦换热器设计

中国散裂中子源工程(CSNS)采用氦制冷循环冷却超临界氢至20 K温区,进而用低温超临界氢慢化中子。根据冷却系统的运行工况和参数要求,使用MUSE软件对氢氦换热器进行设计计算,并分析了其压力、温度、传热系数的沿程分布。结果显示氦气侧的压降限制主导了换热器的主要结构尺寸。由于氦制冷机的氦气压力和质量流量较低,氦气侧的传热系数较低,研究表明这是该换热器性能提升的瓶颈。     

中国散裂中子源RCS真空系统

快循环同步加速器(RCS)作为中国散裂中子源(CSNS)的重要组成部分,主要功能是接受来自直线加速器加速至80MeV的负氢离子束,通过剥离膜转换成质子束并累计加速到1.6GeV引出,经RTBT传输至靶站打靶产生中子.RCS真空系统是实现这一功能的重要载体.本文从RCS总体布局入手,主要介绍RCS真空系统结构设计、设备布...     

中国散裂中子源低温系统氦制冷系统的安装与调试

氦制冷系统是中国散裂中子源(CSNS)低温系统的重要组成部分,能够为氢循环系统提供2 200 W@20 K的冷源。介绍了CSNS氦制冷系统的组成及设备布局图及氦制冷系统的调试原理,完成了控制界面图及氦制冷系统的安装和调试准备工作,详细说明了调试的过程,获得了700 W/1 400 W/2 200 W 3种制冷功率下的状态参数。氦制冷系统调试顺利完成,结果满足了验收指标。     

中国散裂中子源4K低温恒温器温度校正

介绍了中国散裂中子源(CSNS)一期4 K低温恒温器的结构、性能测试及样品温度测试结果。测试结果显示样品座测点温度与实际样品温度存在温差,所以必须对样品温度进行校正。通过对样品区域进行热工分析,设计了可以密封氦气的样品盒,实现了测点温度与样品温度的一致。     

ADS系统中子散裂靶的传热分析

在加速器驱动的次临界核能系统（简称ADS）的研究中，中子散裂靶的散热是一个重要的课题。本文阐述了散裂靶的选择，并利用LAHET程序模拟高能质子引起靶核散裂的过程，计算靶中的能量沉积，以及利用PHOENICS程序，在不同的功率状态对固体靶区进行散热分析。结果表明，在靶区功率较高的情况下，固体靶的传热效果差。因此，使用液体靶，将是更合理的选择。     

中国散裂中子源低温系统调试及运行进展（英文）

中国散裂中子源(简称CSNS)低温系统的主要作用是为靶站慢化器提供满足温度和压力要求的低温超临界氢。低温系统的调试历经1年,主要包括4个方面:(1)氦制冷机验收测试,使用制冷机内部的加热器作为热负载,测试制冷机的制冷量;(2)氦降温测试,使用模拟负载模拟慢化器动态热负荷,采用氦气降温至20K后复温并检漏。(3)氢降温测试,采样氢降温至20K并优化控制逻辑。(4)低温系统与慢化器的联合降温测试。CSNS低温系统目前已经完成了所有调试工作,并配合靶站谱仪的调试工作完成5次较长时间的持续稳定运行。     

Target station shielding issues at the spallation neutron source

Recent spallation neutron source shielding activities in support of the neutron beam shutters and the hot cell walls are presented. Existing neutron beam shutters can be replaced with concrete at low power or with concrete and steel at approximately 500 kW of beam power. Potential voids in the hot cell walls are analysed to determine the impact on dose rates as a function of void size. A change in the type of shielding work is noted as the project moved from the early design stages as a 'green field' site to the current stage as a construction project nearing completion, where issues to be addressed are approaching retrofit-type analyses.     

Activation calculations for the target of a spallation ultra-cold neutron source at PSI

A spallation ultra-cold neutron source--UCN source--is scheduled to start operation at PSI in 2006 using up to 2 mA 590 MeV protons from the ring cyclotron. It will be operated in a pulsed mode with an average current of 20 microA. For safe maintenance, during operation as well as handling, transport and storage of the UCN target assembly after its lifespan, detailed knowledge about the activation induced by the impinging protons and secondary radiation fields is required. The Monte Carlo transport code MCNPX was coupled with the European Activation System--EASY--to calculate the residual nuclide production in the UCN target assembly. The nuclide inventory is finally used to design the shielded exchange flask that is needed to safely remove and transport the UCN target assembly after its lifespan to a hotcell for dismantling.     

Initial neutronic target station studies for the national spallation neutron source (NSNS)

Results found during initial NSNS target station neutronic design efforts are reported including the success of comparing neutron sources at 1 eV and moderator performance normalized to 1 eV. The usefulness of an analytic form is demonstrated. The angular dependence of the neutron current from a moderator face is presented together with the changes in neutron current with variation of moderator width, poison plate location and moderator material. The formation of an equilibrium state at low neutron energy is also discussed.     

Water target at the ISIS spallation source: neutrino and neutron fluxes

Effects arising from a water target places in the ISIS spallation facility, used for both neutron and neutrino experiments, are considered. Calculations are presented for the neutrino flux from stopped μ⁺ decay, and for the neutron fluxes from the ISIS moderators, for several versions of a water target situated upstream of the ISIS spallation source. Two possible configurations, that enhance the neutrino flux by 39–80% and produce relatively little reduction in neutron flux, are outlined.     

-Ray background sources in the VESUVIO spectrometer at ISIS spallation neutron source

An investigation of the gamma background was carried out in the VESUVIO spectrometer at the ISIS spallation neutron source. This study, performed with a yttrium–aluminum–perovskite (YAP) scintillator, follows high resolution pulse height measurements of the gamma background carried out on the same instrument with the use of a high-purity germanium detector. In this experimental work, a mapping of the gamma background was attempted, trying to find the spatial distribution and degree of directionality of the different contributions identified in the previous study. It is found that the gamma background at low times is highly directional and mostly due to the gamma rays generated in the moderator–decoupler system. The other contributions, consistently to the findings of a previous experiment, are identified as a nearly isotropic one due to neutron absorption in the walls of the experimental hall, and a directional one coming from the beam dump.     

CW accelerators suitable for spallation neutron sources

An accelerator-driven steady state neutron source will require a high current, high energy, 100% duty factor accelerator. No suitable accelerator has yet been built, but the technology to do so existsand examples of all of the likely components have been tested. This paper reviews some of the component test programs with comments on the problems specific to this application.     

Advantages and limitations of nuclear physics experiments at an ISIS-class spallation neutron source

Nuclear physics experiments have a long history of being conducted on spallation neutron sources. Like other experiments, these measurements take advantage of the identification of the incident neutron energy by the time-of-flight (ToF) technique. However, in some ways these experiments are often in direct conflict with other experiments. Especially in large (ISIS or SNS class) facilities, the design of the source often reflects a compromise between different experimental needs and requirements. It has been a long standing question for nuclear physics experiments how limiting these compromises are and how they can be dealt with. We have therefore calculated the incident neutron energy spectrum, along with the gamma background spectrum, for flight path (FP) 5 at the Los Alamos Neutron Science Center (LANSCE) Manuel Lujan Jr. Neutron Scattering Center (Lujan Center) including a detailed evaluation of the signal shape. We will discuss the advantages and limitations of the nuclear physics experiments at FP-5 in the light of our results.