The Moon has been divided into three terranes:Procellarum KREEP Terrane(PKT),Feldspathic Highland Terrane(FHT),and South Pole-Aitken Terrane(SPAT),using globally measured Th and FeO.Many lunar evolu-tion models have p...The Moon has been divided into three terranes:Procellarum KREEP Terrane(PKT),Feldspathic Highland Terrane(FHT),and South Pole-Aitken Terrane(SPAT),using globally measured Th and FeO.Many lunar evolu-tion models have predicted that a lunar magma ocean will produce a residual layer enriched in incompatible elements such as K,REE,and P(i.e.,KREEP)in the late age of crys-tallization;and that the distribution of thorium can be used as a proxy for determining the global distribution of KREEP.The thorium distribution in these three terranes is inhomo-geneous.The highest concentration of thorium is in PKT,the medium concentration of thorium is in SPAT,and almost none in FHT.Then what is the specific distribution in each of the terrane and what enlightenment can it tell us?Here we present and describe the detailed thorium distribution in PKT,SPAT,and FHT and provide some information for the origin of asymmetries on the lunar surface.展开更多
Nucleco is the Sogin Group’s Italian leading company in the sector of radiological services,radioactive waste management,decontamination and reclamation of industrial sites and nuclear power plants.Nucleco is 60%owne...Nucleco is the Sogin Group’s Italian leading company in the sector of radiological services,radioactive waste management,decontamination and reclamation of industrial sites and nuclear power plants.Nucleco is 60%owned by Sogin and 40%by ENEA-National Agency for New Technologies.The waste characterization carried out by Nucleco SpA includes a large variety of radionuclides belonging to the gamma,beta and alpha emitter families.The determination of Uranium and Plutonium isotopes plays a key role in the waste characterization.Nucleco SpA has distinguished itself in characterizations of radioactive waste in complex and nuclear plant matrices.These matrices have large amounts of alpha emitters,in particular isotopes of Uranium,Thorium and Plutonium.A significant presence of U238 results in such a large amount of Th234(and daughters)that interferes with the determination of Pu241.Hence,there is the need of finding a pre-treatment,extraction and subsequent purification technique that would allow Th234 to be detached and thus Pu241 to be determined in complex high-activity matrices.The above elements are extracted using chromatography columns.An isotope of the element to be analyzed,with known activity,is added at the beginning of the process to determine the extraction yield.Before being eluted into the column,the sample undergoes a series of treatments in order to be purified of any interferents.The method developed by Nucleco involves the oxidation of Pu at valence+6 and the subsequent precipitation,in fluorides form,of the elements with valence+4 and+3(i.e.Th234).Pu241 is then measured by LSC(Liquid Scintillation Counting),while the other isotopes are measured by alpha spectrometry after electrodeposition on a metal plate.展开更多
功率控制系统(Power Control System,PCS)是反应堆控制系统(Reactor Control System,RCS)的重要组成部分,它完成功率提升、功率保持与功率调节的作用。在钍基熔盐堆(Thorium Molten Salt Reactor,TMSR)核能系统固态堆设计方案中,功率控...功率控制系统(Power Control System,PCS)是反应堆控制系统(Reactor Control System,RCS)的重要组成部分,它完成功率提升、功率保持与功率调节的作用。在钍基熔盐堆(Thorium Molten Salt Reactor,TMSR)核能系统固态堆设计方案中,功率控制器根据实测功率与设定功率值之间的偏差和偏差的变化趋势,按照经典的比例-积分-微分(Proportional Integral Derivative,PID)控制算法,给出调节控制棒的运动距离和运动方向等信号。PCS的PID算法设计与基于反应堆中子物理、热工及控制棒的传动性能构成的闭环控制系统的特性有关,其不同参数的确定与系统的静态和动态性能指标的要求相对应。本文从控制的角度出发,在已有的控制棒样机中设计的棒控棒位系统及相关中子物理的基础上对PCS的PID算法进行多层次仿真与参数分析,并对系统的可控性与可测性进行分析验证。分析及仿真结果表明两种控制模型下的系统均是完全可控及完全可测的,在合适的PID参数集下均能体现响应的快速性及系统的良好鲁棒性和抗干扰能力,具有实际的应用意义。展开更多
中子动态参数的准确分析与反应堆的安全特性紧密相关。固态燃料钍基熔盐实验堆(Thorium-based Molten Salt experiment Reactor with Solid Fuel,TMSR-SF1)作为第四代新堆型,采用蒙特卡罗输运程序计算其动态参数更有利于核安全评审。本...中子动态参数的准确分析与反应堆的安全特性紧密相关。固态燃料钍基熔盐实验堆(Thorium-based Molten Salt experiment Reactor with Solid Fuel,TMSR-SF1)作为第四代新堆型,采用蒙特卡罗输运程序计算其动态参数更有利于核安全评审。本文基于较通用的蒙特卡罗多粒子输运(Monte Carlo N Particle Transport Code,MCNP)程序,植入了动态参数直接统计方法,用于计算TMSR-SF1中的有效缓发中子份额和有效中子代时间。通过多个ICSBEP(International Criticality Safety Benchmark Evaluation Project)基准题的检验,计算结果与基准题实验误差在±5%以内,证明了该方法的准确性。运用该方法计算得到TMSR-SF1中6组有效缓发中子份额和有效中子代时间随燃耗深度的变化,其计算结果与采用MCNP共轭通量方法所得的数据误差在±3%以内,证明该方法用于TMSR-SF1的动态参数分析是合理可靠的。展开更多
基金This work was supported by National Key Research and Development Program of China(Grant No.2022YFF0503100)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB 41000000).
文摘The Moon has been divided into three terranes:Procellarum KREEP Terrane(PKT),Feldspathic Highland Terrane(FHT),and South Pole-Aitken Terrane(SPAT),using globally measured Th and FeO.Many lunar evolu-tion models have predicted that a lunar magma ocean will produce a residual layer enriched in incompatible elements such as K,REE,and P(i.e.,KREEP)in the late age of crys-tallization;and that the distribution of thorium can be used as a proxy for determining the global distribution of KREEP.The thorium distribution in these three terranes is inhomo-geneous.The highest concentration of thorium is in PKT,the medium concentration of thorium is in SPAT,and almost none in FHT.Then what is the specific distribution in each of the terrane and what enlightenment can it tell us?Here we present and describe the detailed thorium distribution in PKT,SPAT,and FHT and provide some information for the origin of asymmetries on the lunar surface.
文摘Nucleco is the Sogin Group’s Italian leading company in the sector of radiological services,radioactive waste management,decontamination and reclamation of industrial sites and nuclear power plants.Nucleco is 60%owned by Sogin and 40%by ENEA-National Agency for New Technologies.The waste characterization carried out by Nucleco SpA includes a large variety of radionuclides belonging to the gamma,beta and alpha emitter families.The determination of Uranium and Plutonium isotopes plays a key role in the waste characterization.Nucleco SpA has distinguished itself in characterizations of radioactive waste in complex and nuclear plant matrices.These matrices have large amounts of alpha emitters,in particular isotopes of Uranium,Thorium and Plutonium.A significant presence of U238 results in such a large amount of Th234(and daughters)that interferes with the determination of Pu241.Hence,there is the need of finding a pre-treatment,extraction and subsequent purification technique that would allow Th234 to be detached and thus Pu241 to be determined in complex high-activity matrices.The above elements are extracted using chromatography columns.An isotope of the element to be analyzed,with known activity,is added at the beginning of the process to determine the extraction yield.Before being eluted into the column,the sample undergoes a series of treatments in order to be purified of any interferents.The method developed by Nucleco involves the oxidation of Pu at valence+6 and the subsequent precipitation,in fluorides form,of the elements with valence+4 and+3(i.e.Th234).Pu241 is then measured by LSC(Liquid Scintillation Counting),while the other isotopes are measured by alpha spectrometry after electrodeposition on a metal plate.
文摘功率控制系统(Power Control System,PCS)是反应堆控制系统(Reactor Control System,RCS)的重要组成部分,它完成功率提升、功率保持与功率调节的作用。在钍基熔盐堆(Thorium Molten Salt Reactor,TMSR)核能系统固态堆设计方案中,功率控制器根据实测功率与设定功率值之间的偏差和偏差的变化趋势,按照经典的比例-积分-微分(Proportional Integral Derivative,PID)控制算法,给出调节控制棒的运动距离和运动方向等信号。PCS的PID算法设计与基于反应堆中子物理、热工及控制棒的传动性能构成的闭环控制系统的特性有关,其不同参数的确定与系统的静态和动态性能指标的要求相对应。本文从控制的角度出发,在已有的控制棒样机中设计的棒控棒位系统及相关中子物理的基础上对PCS的PID算法进行多层次仿真与参数分析,并对系统的可控性与可测性进行分析验证。分析及仿真结果表明两种控制模型下的系统均是完全可控及完全可测的,在合适的PID参数集下均能体现响应的快速性及系统的良好鲁棒性和抗干扰能力,具有实际的应用意义。
文摘中子动态参数的准确分析与反应堆的安全特性紧密相关。固态燃料钍基熔盐实验堆(Thorium-based Molten Salt experiment Reactor with Solid Fuel,TMSR-SF1)作为第四代新堆型,采用蒙特卡罗输运程序计算其动态参数更有利于核安全评审。本文基于较通用的蒙特卡罗多粒子输运(Monte Carlo N Particle Transport Code,MCNP)程序,植入了动态参数直接统计方法,用于计算TMSR-SF1中的有效缓发中子份额和有效中子代时间。通过多个ICSBEP(International Criticality Safety Benchmark Evaluation Project)基准题的检验,计算结果与基准题实验误差在±5%以内,证明了该方法的准确性。运用该方法计算得到TMSR-SF1中6组有效缓发中子份额和有效中子代时间随燃耗深度的变化,其计算结果与采用MCNP共轭通量方法所得的数据误差在±3%以内,证明该方法用于TMSR-SF1的动态参数分析是合理可靠的。
