It is a commonly asked question:how big should the longwall shields be? The answer is a key aspect of a longwall mining feasibility study when the consequences of inadequately rated shields are considered.This paper a...It is a commonly asked question:how big should the longwall shields be? The answer is a key aspect of a longwall mining feasibility study when the consequences of inadequately rated shields are considered.This paper addresses this question based on the measured nature of the loading environment in which shields are required to operate,the various geological and geometrical controls of that environment and the various links between their load rating,a range of other relevant shield design factors and the loss event they are required to prevent a major roof collapse on the longwall face.The paper concludes that despite the tremendous advances that have been made in shield design and load rating over the past50 years,the same drivers that caused longwall miners of the past to seek improved roof control on the longwall face via the use of ever-higher rated shields,are still as relevant today.However at the current time,the limits of the largest available longwall shields have yet to be tested,therefore industry focus for the foreseeable future should possibly be in achieving the maximum level of roof control on the face via their optimum operational use rather than considering further shield rating increases and incurring the inevitable downsides in terms of capital cost and shield weight.展开更多
A three-wave based laser polarimeter/interferometer and a CO_(2)laser dispersion interferometer are used to determine the electron and current density profiles on a Chinese fusion engineering test reactor(CFETR).Radia...A three-wave based laser polarimeter/interferometer and a CO_(2)laser dispersion interferometer are used to determine the electron and current density profiles on a Chinese fusion engineering test reactor(CFETR).Radiation shielding is designed for the combination of polarimeter/interferometer and CO_(2)dispersion interferometer.Furthermore,neutronics models of the two systems are developed based on the engineering-integrated design of CFETR polarimeter/interferometer and CO_(2)dispersion interferometer and the major material components of CFETR.The polarimeter/interferometer and CO_(2)dispersion interferometer's neutron and photon transport simulations were performed using the Monte Carlo neutral transport code to determine the energy deposition and neutron energy spectrum of the optical mirrors.The energy depositions of the first mirrors on the polarimeter/interferometer are reduced by three orders with the whole shielding.Since the mirrors of CO_(2)dispersion interferometer are very close to the diagnostic first wall,shielding space is limited and the CO_(2)dispersion interferometer energy deposition is higher than that of the polarimeter/interferometer.The dose rate after shutdown106s in the back-drawer structure has been estimated to be 83μSv h^(-1)when the radiation shield is filled in the diagnostic shielding modules,which is below the design threshold of 100μSv h^(-1).Radiation shielding design plays a key role in successfully applying polarimeter/interferometer and CO_(2)dispersive interferometer in CFETR.展开更多
针对核医学发展需求,本研究提出将直线加速器机房改建为回旋加速器机房的解决方案。通过理论计算与MCNP(Monte Carlo N-particle transport code)模拟,评估原重混凝土机房(厚度1.2~2.6 m)对γ射线的屏蔽效能,并针对中子辐射提出内壁增...针对核医学发展需求,本研究提出将直线加速器机房改建为回旋加速器机房的解决方案。通过理论计算与MCNP(Monte Carlo N-particle transport code)模拟,评估原重混凝土机房(厚度1.2~2.6 m)对γ射线的屏蔽效能,并针对中子辐射提出内壁增设含硼聚乙烯(24~48 cm)的优化方案。结果表明:原有混凝土结构满足γ防护要求,选择屏蔽中子效率高、次生γ增量少的含硼聚乙烯,经模拟验证剂量率水平较低;采用聚乙烯慢化层与含硼聚乙烯(11%)吸收层组合,有效避免铁矿石骨料的中子活化风险;该方案施工难度低,成本可控,能够实现医疗设施高效再利用。本研究为同类改造提供技术参考,符合我国核医学高质量发展政策需求。展开更多
High magnetic field shielding has been increasingly important for engineering design in recent years. In this report, a cylindric shield made from soft iron is studied using FEM （finite element method） analysis and ...High magnetic field shielding has been increasingly important for engineering design in recent years. In this report, a cylindric shield made from soft iron is studied using FEM （finite element method） analysis and COlnpared with experiments. The residual fields inside the shield are calculated and measured in both parallel and perpendicular fields up to 2000 Gs. The calculated results are compared with the experiments, and the input B-H curve is modified for a better conformity. The results indicate that the covers could greatly improve the shielding performance of the cylindric shield in our research. The comparison result shows that a proper B-H curve, which can well describe the material properties, is very important in FEM analysis and should be selected carefully.展开更多
Shielding angle is one of the main factors influencing lightning performance of transmission lines,which always stays in the focus of the design and the evaluation of lightning protection.A formula for the improved sh...Shielding angle is one of the main factors influencing lightning performance of transmission lines,which always stays in the focus of the design and the evaluation of lightning protection.A formula for the improved shielding angle is proposed for evaluating the lightning performance in different terrains.The digital elevation model(DEM) is used to obtain the micro-topography data,such as the slope gradient,slope aspect,etc.The following results are obtained by analyzing the influence of topography factors on the improved shielding angle:(1) improved shielding angle non-linearly increases with the increase of the slope gradient and the slope aspect,(2) improved shielding angle is more sensitive to the slope gradient than to the slope aspect,(3) the improved shielding angle in the mountain terrains is much greater than the designed shielding angle.This may be the reason why the designed shielding angle is limited into the rational range,while the shielding faults occur frequently.展开更多
The weldability of a ferritic ductile cast iron was investigated as a function of different consumables and welding conditions. A 23 full factorial experimental design was used to analyze the effect of factors and the...The weldability of a ferritic ductile cast iron was investigated as a function of different consumables and welding conditions. A 23 full factorial experimental design was used to analyze the effect of factors and their interac- tions on ultimate tensile strength of weldments. The shielded metal arc welding （SMAW） process was used with two types of consumables （E7018 and ENi-CI） under eight different conditions using as-cast samples. The microstructur- al evolution and fracture mechanisms were investigated by optical microscopy and scanning electron microscopy （SEM）, respectively. The hardness, tensile and impact tests were also performed to determine the weld quality. Based on experiment design, preheat, consumable, cooling condition, preheat cooling and preheat-consumable inter- actions were significant factors. Preheat is the most effective factor and in the case of E7018, preheat and cooling conditions were the most sensible factors. It was found that buttering was the most appropriate welding method for ferritic ductile cast iron.展开更多
宽能谱超高通量试验堆(Tsinghua High Flux Reactor,THFR)是一种具备国际先进水平的水冷高通量反应堆,其辐照孔道未扰动的平均热、快中子通量可达2×10^(15)n·cm^(-2)·s^(-1),具有中子通量高、能谱范围宽、辐照能力强、...宽能谱超高通量试验堆(Tsinghua High Flux Reactor,THFR)是一种具备国际先进水平的水冷高通量反应堆,其辐照孔道未扰动的平均热、快中子通量可达2×10^(15)n·cm^(-2)·s^(-1),具有中子通量高、能谱范围宽、辐照能力强、功能用途广等突出特点,综合辐照性能居于国际领先水平,在工业、农业、航天、医疗等领域具有重要应用。本文分析了THFR反应堆及相关系统、辐照应用系统的设计特点,包括采用“池壳式”堆本体结构、“低中子自屏”堆芯设计、弧板型燃料组件、旋转控制鼓、多用途辐照孔道设计、“能动-非能动”相结合安全系统设计等,并对该堆在核燃料和材料辐照考验、放射性同位素辐照生产、中子科学研究等领域的应用前景进行了展望。THFR为服务国家重大战略需求、保障人民生命健康、培育和发展新质生产力提供了有力支撑。展开更多
文摘It is a commonly asked question:how big should the longwall shields be? The answer is a key aspect of a longwall mining feasibility study when the consequences of inadequately rated shields are considered.This paper addresses this question based on the measured nature of the loading environment in which shields are required to operate,the various geological and geometrical controls of that environment and the various links between their load rating,a range of other relevant shield design factors and the loss event they are required to prevent a major roof collapse on the longwall face.The paper concludes that despite the tremendous advances that have been made in shield design and load rating over the past50 years,the same drivers that caused longwall miners of the past to seek improved roof control on the longwall face via the use of ever-higher rated shields,are still as relevant today.However at the current time,the limits of the largest available longwall shields have yet to be tested,therefore industry focus for the foreseeable future should possibly be in achieving the maximum level of roof control on the face via their optimum operational use rather than considering further shield rating increases and incurring the inevitable downsides in terms of capital cost and shield weight.
基金the National MCF Energy R&D Program of China(Nos.2019YFE03040003 and 2017YFE0301205)Key Program of Research and Development of Hefei Science Center,CAS(No.2019HSC-KPRD001)supported in part by the Collaborative Research Program of the Research Institute for Applied Mechanics,Kyushu University。
文摘A three-wave based laser polarimeter/interferometer and a CO_(2)laser dispersion interferometer are used to determine the electron and current density profiles on a Chinese fusion engineering test reactor(CFETR).Radiation shielding is designed for the combination of polarimeter/interferometer and CO_(2)dispersion interferometer.Furthermore,neutronics models of the two systems are developed based on the engineering-integrated design of CFETR polarimeter/interferometer and CO_(2)dispersion interferometer and the major material components of CFETR.The polarimeter/interferometer and CO_(2)dispersion interferometer's neutron and photon transport simulations were performed using the Monte Carlo neutral transport code to determine the energy deposition and neutron energy spectrum of the optical mirrors.The energy depositions of the first mirrors on the polarimeter/interferometer are reduced by three orders with the whole shielding.Since the mirrors of CO_(2)dispersion interferometer are very close to the diagnostic first wall,shielding space is limited and the CO_(2)dispersion interferometer energy deposition is higher than that of the polarimeter/interferometer.The dose rate after shutdown106s in the back-drawer structure has been estimated to be 83μSv h^(-1)when the radiation shield is filled in the diagnostic shielding modules,which is below the design threshold of 100μSv h^(-1).Radiation shielding design plays a key role in successfully applying polarimeter/interferometer and CO_(2)dispersive interferometer in CFETR.
文摘针对核医学发展需求,本研究提出将直线加速器机房改建为回旋加速器机房的解决方案。通过理论计算与MCNP(Monte Carlo N-particle transport code)模拟,评估原重混凝土机房(厚度1.2~2.6 m)对γ射线的屏蔽效能,并针对中子辐射提出内壁增设含硼聚乙烯(24~48 cm)的优化方案。结果表明:原有混凝土结构满足γ防护要求,选择屏蔽中子效率高、次生γ增量少的含硼聚乙烯,经模拟验证剂量率水平较低;采用聚乙烯慢化层与含硼聚乙烯(11%)吸收层组合,有效避免铁矿石骨料的中子活化风险;该方案施工难度低,成本可控,能够实现医疗设施高效再利用。本研究为同类改造提供技术参考,符合我国核医学高质量发展政策需求。
文摘High magnetic field shielding has been increasingly important for engineering design in recent years. In this report, a cylindric shield made from soft iron is studied using FEM （finite element method） analysis and COlnpared with experiments. The residual fields inside the shield are calculated and measured in both parallel and perpendicular fields up to 2000 Gs. The calculated results are compared with the experiments, and the input B-H curve is modified for a better conformity. The results indicate that the covers could greatly improve the shielding performance of the cylindric shield in our research. The comparison result shows that a proper B-H curve, which can well describe the material properties, is very important in FEM analysis and should be selected carefully.
基金Project supported by National Natural Science Foundation of China （51277064）.
文摘Shielding angle is one of the main factors influencing lightning performance of transmission lines,which always stays in the focus of the design and the evaluation of lightning protection.A formula for the improved shielding angle is proposed for evaluating the lightning performance in different terrains.The digital elevation model(DEM) is used to obtain the micro-topography data,such as the slope gradient,slope aspect,etc.The following results are obtained by analyzing the influence of topography factors on the improved shielding angle:(1) improved shielding angle non-linearly increases with the increase of the slope gradient and the slope aspect,(2) improved shielding angle is more sensitive to the slope gradient than to the slope aspect,(3) the improved shielding angle in the mountain terrains is much greater than the designed shielding angle.This may be the reason why the designed shielding angle is limited into the rational range,while the shielding faults occur frequently.
文摘The weldability of a ferritic ductile cast iron was investigated as a function of different consumables and welding conditions. A 23 full factorial experimental design was used to analyze the effect of factors and their interac- tions on ultimate tensile strength of weldments. The shielded metal arc welding （SMAW） process was used with two types of consumables （E7018 and ENi-CI） under eight different conditions using as-cast samples. The microstructur- al evolution and fracture mechanisms were investigated by optical microscopy and scanning electron microscopy （SEM）, respectively. The hardness, tensile and impact tests were also performed to determine the weld quality. Based on experiment design, preheat, consumable, cooling condition, preheat cooling and preheat-consumable inter- actions were significant factors. Preheat is the most effective factor and in the case of E7018, preheat and cooling conditions were the most sensible factors. It was found that buttering was the most appropriate welding method for ferritic ductile cast iron.
文摘宽能谱超高通量试验堆(Tsinghua High Flux Reactor,THFR)是一种具备国际先进水平的水冷高通量反应堆,其辐照孔道未扰动的平均热、快中子通量可达2×10^(15)n·cm^(-2)·s^(-1),具有中子通量高、能谱范围宽、辐照能力强、功能用途广等突出特点,综合辐照性能居于国际领先水平,在工业、农业、航天、医疗等领域具有重要应用。本文分析了THFR反应堆及相关系统、辐照应用系统的设计特点,包括采用“池壳式”堆本体结构、“低中子自屏”堆芯设计、弧板型燃料组件、旋转控制鼓、多用途辐照孔道设计、“能动-非能动”相结合安全系统设计等,并对该堆在核燃料和材料辐照考验、放射性同位素辐照生产、中子科学研究等领域的应用前景进行了展望。THFR为服务国家重大战略需求、保障人民生命健康、培育和发展新质生产力提供了有力支撑。
