In this paper, we study a monitoring method for neutron flux for the spaUation target used in an accelerator driven sub-critical （ADS） system, where a spallation target located vertically at the centre of a sub-crit...In this paper, we study a monitoring method for neutron flux for the spaUation target used in an accelerator driven sub-critical （ADS） system, where a spallation target located vertically at the centre of a sub-critical core is bombarded vertically by high-energy protons from an accelerator. First, by considering the characteristics in the spatial variation of neutron flux from the spallation target, we propose a multi-point measurement technique, i.e. the spallation neutron flux should be measured at multiple vertical locations. To explain why the flux should be measured at multiple locations, we have studied neutron production from a tungsten target bombarded by a 250 MeV-proton beam with Geant4-based Monte Carlo simulations. The simulation results indicate that the neutron flux at the central location is up to three orders of magnitude higher than the flux at lower locations. Secondly, we have developed an effective technique in order to measure the spallation neutron flux with a fission chamber （FC）, by establishing the relation between the fission rate measured by FC and the spallation neutron flux. Since this relation is linear for a FC, a constant calibration factor is used to derive the neutron flux from the measured fission rate. This calibration factor can be extracted from the energy spectra of spallation neutrons. Finally, we have evaluated the proposed calibration method for a FC in the environment of an ADS system. The results indicate that the proposed method functions very well.展开更多
基于固体和液体散裂靶,近期国内外研究学者提出了一种新概念重金属颗粒流散裂靶。加速器驱动次临界系统(ADS)中重金属散裂靶在高能质子轰击作用下,出现能量沉积现象,而这些热量必须进行有效冷却以保证ADS的安全性。本文针对这种新概念...基于固体和液体散裂靶,近期国内外研究学者提出了一种新概念重金属颗粒流散裂靶。加速器驱动次临界系统(ADS)中重金属散裂靶在高能质子轰击作用下,出现能量沉积现象,而这些热量必须进行有效冷却以保证ADS的安全性。本文针对这种新概念颗粒流靶对靶区产生的高额热量的导出效果进行了模拟分析。首先采用蒙特卡罗程序计算450 Me V质子束轰击钨靶后能量沉积的空间分布,并将此作为颗粒流的体热源输入,基于计算流体力学-离散单元法(CFD-DEM)耦合方法对ADS靶区两种不同直径颗粒流的输运过程进行了模拟研究。结果表明,随颗粒直径的减小,靶区内温度分布更为均匀,颗粒流的流动特性更接近流体,颗粒导热性能增强;颗粒流靶中热应力可局限在单个颗粒内部而承受更高的能量沉积,具有更高的安全限值以及更广阔的应用前景。展开更多
EP-823 steel is one of the candidate materials for accelerator-driven systems/lead-cooled fast reactors （ADS/LFR）. Its weldability was investigated by mechanical property tests and microstructure analysis on the enl...EP-823 steel is one of the candidate materials for accelerator-driven systems/lead-cooled fast reactors （ADS/LFR）. Its weldability was investigated by mechanical property tests and microstructure analysis on the enlarged heat-affected zones （HAZs） made by numerical and physical simulation. The finite element numerical simulation could simulate the welding thermal cycle of the characteristic regions in HAZs with extremely high accuracy, The physical simulation performed on a Gleeble simulator could enlarge the characteristic regions to easily investigate the relationship between the microstructure evolution and the mechanical properties of the HAZs. The results showed that the simulated partially normalized zone comprising tempered martensite, newly formed martensite and more tiny carbides has the highest impact energy. The fully normalized zone exhibits the highest hardness because of the quenched martensite and large carbides. The ductile property of the overheated zone is poor for the residual delta- ferrite phases and the quenched martensite.展开更多
基金Supported by Strategic Priority Research Program of Chinese Academy of Sciences(XDA03010000 and XDA03030000)the National Natural Science Foundation of China(91426301)
文摘In this paper, we study a monitoring method for neutron flux for the spaUation target used in an accelerator driven sub-critical （ADS） system, where a spallation target located vertically at the centre of a sub-critical core is bombarded vertically by high-energy protons from an accelerator. First, by considering the characteristics in the spatial variation of neutron flux from the spallation target, we propose a multi-point measurement technique, i.e. the spallation neutron flux should be measured at multiple vertical locations. To explain why the flux should be measured at multiple locations, we have studied neutron production from a tungsten target bombarded by a 250 MeV-proton beam with Geant4-based Monte Carlo simulations. The simulation results indicate that the neutron flux at the central location is up to three orders of magnitude higher than the flux at lower locations. Secondly, we have developed an effective technique in order to measure the spallation neutron flux with a fission chamber （FC）, by establishing the relation between the fission rate measured by FC and the spallation neutron flux. Since this relation is linear for a FC, a constant calibration factor is used to derive the neutron flux from the measured fission rate. This calibration factor can be extracted from the energy spectra of spallation neutrons. Finally, we have evaluated the proposed calibration method for a FC in the environment of an ADS system. The results indicate that the proposed method functions very well.
文摘基于固体和液体散裂靶,近期国内外研究学者提出了一种新概念重金属颗粒流散裂靶。加速器驱动次临界系统(ADS)中重金属散裂靶在高能质子轰击作用下,出现能量沉积现象,而这些热量必须进行有效冷却以保证ADS的安全性。本文针对这种新概念颗粒流靶对靶区产生的高额热量的导出效果进行了模拟分析。首先采用蒙特卡罗程序计算450 Me V质子束轰击钨靶后能量沉积的空间分布,并将此作为颗粒流的体热源输入,基于计算流体力学-离散单元法(CFD-DEM)耦合方法对ADS靶区两种不同直径颗粒流的输运过程进行了模拟研究。结果表明,随颗粒直径的减小,靶区内温度分布更为均匀,颗粒流的流动特性更接近流体,颗粒导热性能增强;颗粒流靶中热应力可局限在单个颗粒内部而承受更高的能量沉积,具有更高的安全限值以及更广阔的应用前景。
基金financial support from the National Natural Science Foundation of China(NSFC)under grant No.91226204the Chinese Academy of Science Strategic Pilot Project(The Future of Advanced Nuclear Energy,ADS Evolution System)under grant No.XDA03010304
文摘EP-823 steel is one of the candidate materials for accelerator-driven systems/lead-cooled fast reactors （ADS/LFR）. Its weldability was investigated by mechanical property tests and microstructure analysis on the enlarged heat-affected zones （HAZs） made by numerical and physical simulation. The finite element numerical simulation could simulate the welding thermal cycle of the characteristic regions in HAZs with extremely high accuracy, The physical simulation performed on a Gleeble simulator could enlarge the characteristic regions to easily investigate the relationship between the microstructure evolution and the mechanical properties of the HAZs. The results showed that the simulated partially normalized zone comprising tempered martensite, newly formed martensite and more tiny carbides has the highest impact energy. The fully normalized zone exhibits the highest hardness because of the quenched martensite and large carbides. The ductile property of the overheated zone is poor for the residual delta- ferrite phases and the quenched martensite.
