This study aims to produce 229Th using an innovative nuclear reactor concept,i.e.,accelerator-driven system(ADS)reactor.Herein,we investigated the feasibility of producing 229Th from neutron transmutation of 226Ra to ...This study aims to produce 229Th using an innovative nuclear reactor concept,i.e.,accelerator-driven system(ADS)reactor.Herein,we investigated the feasibility of producing 229Th from neutron transmutation of 226Ra to expand the availability of 225Ac and 213Bi in a simple model of ADS reactor.ADS reactor comprises two zones,i.e.,an inner zone with a fast neutron spectrum and outer zone with thermal neutron spectrum,which is a subcritical core coupled with an external neutron source.Transmutation behavior,activity,and mass ratio of the obtained isotopes were investigated using the Monte-Carlo tool.In addition with offering the capability,flexibility,and safety of radioactive waste transmutation,the proposed ADS model provides high 229Th yield and requires less time than a critical reactor with the same neutron flux and irradiated quantity of 226Ra.展开更多
During the 134 （1996 1997） and the 19th （2002-2003） Chinese National Antarctica Research Expeditions, we collected 60 discrete surface seawater samples along the cruise from the Chanjiang River （Yangtze） estuary...During the 134 （1996 1997） and the 19th （2002-2003） Chinese National Antarctica Research Expeditions, we collected 60 discrete surface seawater samples along the cruise from the Chanjiang River （Yangtze） estuary （30^.59%, 122^.26＇E） through Taiwan Strait, the South China Sea, and the Eastern Indian Ocean to Prydz Bay, Antarctica （69^.10＇S, 74^.30＇E）, and analyzed them for the 226Ra specific activity. The 226Ra specific activity of the Chanjiang River estuary surface water （3.15 Bq/m3） was found to be the highest among all the surface samples because of the desorption of 226Ra from riverine particles. Between Chanjiang River estuary and 40^.S, 226Ra specific activity was found to be relatively uniform with a mean value of 1.07 Bq/m3 （n= 19, SD=0.14）, similar to that of the open ocean. From 40^.S to 65^.S, 226Ra specific activity increased intensively, then decreased moderately further southwards. Near the Antarctic shore, it increased again, to 2.31 Bq/m3. This distribution was controlled by a combination of deep water upwelling, Southern Ocean fronts, water mixing and the continental 226Ra import. In Prydz Bay and the adjacent sea area, the mean 226Ra activity value was 2.26 Bq/m3 （n=31, SD=0.28）, with a relatively higher value outside of the bay and low 226Ra activity value in the center of the bay. This was consistent with the topography and hydrological setting of the bay. In addition, we extended the study area northward to the Arctic, by combining the published Z26Ra dataset for surface water from the Bering Sea to the Japan Sea. We also discuss the 226Ra distribution of high latitude oceanic surface water and its mechanisms.展开更多
目的了解四川省地表水体中^(226)Ra的放射性水平并对其健康风险进行评估。方法于2016年至2021年间检测了四川省主要地表水系23个监测断面的^(226)Ra放射性水平,应用剂量转换系数计算待积有效剂量,应用健康风险模型评估对居民的健康风险...目的了解四川省地表水体中^(226)Ra的放射性水平并对其健康风险进行评估。方法于2016年至2021年间检测了四川省主要地表水系23个监测断面的^(226)Ra放射性水平,应用剂量转换系数计算待积有效剂量,应用健康风险模型评估对居民的健康风险。结果四川省地表水体中^(226)Ra的放射性水平为1.9 m Bq/L~20.0m Bq/L,所有地表水体中^(226)Ra的放射性水平均合格;不同年度、不同地表水体的^(226)Ra放射性水平间比较,差异均无统计学意义(P>0.05);平水期地表水体的^(226)Ra放射性水平高于枯水期,差异有统计学意义(P<0.05)。通过饮水、水体浸没途径摄入^(226)Ra而所致年均待积有效剂量在各年龄组均低于0.1 m Sv,对各年龄段居民所致的总致癌风险处于9.50×10^(-9)/a~1.004×10^(-7)/a,均低于WHO和ICRP发布的限值(10^(-6)/a和5×10^(-5)/a)。结论四川省主要地表水系中^(226)Ra的放射性水平均未超标,经直接饮水途径、水体浸没途径摄入^(226)Ra所致健康风险处于可接受水平;全省主要地表水体中^(226)Ra的放射性水平对各年龄组都是安全的。展开更多
The biogeochemical processes of marine sediments are influenced by bioturbation and organic carbon decomposition,which is crucial for understanding global element cycles and climate change.Two sediment cores were acqu...The biogeochemical processes of marine sediments are influenced by bioturbation and organic carbon decomposition,which is crucial for understanding global element cycles and climate change.Two sediment cores were acquired in 2017 from abyssal basins in the central-eastern tropical Pacific to determine the bioturbation and organic carbon degradation processes.The radioactivity concentrations of 210Pb and 226Ra in the sediment cores were measured,indicating the presence of significant excess 210Pb(210Pbex)signals in the sediment cores.Besides,a manganese nodule was discovered in one core,which had a substantial influence on the distribution of 210Pbex.With the exception of this anomalous finding,the bioturbation coefficients in the remaining core were estimated to be 10.6 cm^(2)/a using a steady-state diffusion model,greater than most of the deep-sea sediments from the equatorial eastern Pacific.By using a bio-diffusion model,we further calculated the degradation rates of organic carbon(8.02 ka-1),which is also higher than other areas of the Pacific.Our findings displayed the presence of a biologically active benthic ecosystem in the central-eastern tropical Pacific.展开更多
基金supported by the International Center for Theoretical Physics and the Institute of International Education’s Scholar Rescue Fund.
文摘This study aims to produce 229Th using an innovative nuclear reactor concept,i.e.,accelerator-driven system(ADS)reactor.Herein,we investigated the feasibility of producing 229Th from neutron transmutation of 226Ra to expand the availability of 225Ac and 213Bi in a simple model of ADS reactor.ADS reactor comprises two zones,i.e.,an inner zone with a fast neutron spectrum and outer zone with thermal neutron spectrum,which is a subcritical core coupled with an external neutron source.Transmutation behavior,activity,and mass ratio of the obtained isotopes were investigated using the Monte-Carlo tool.In addition with offering the capability,flexibility,and safety of radioactive waste transmutation,the proposed ADS model provides high 229Th yield and requires less time than a critical reactor with the same neutron flux and irradiated quantity of 226Ra.
基金Supported by the National Natural Science Foundation of China(Nos.40706033 and 40806031)COMRA Program(Nos.DYXM-115-02-1-12 and DY115-01-2-5)
文摘During the 134 （1996 1997） and the 19th （2002-2003） Chinese National Antarctica Research Expeditions, we collected 60 discrete surface seawater samples along the cruise from the Chanjiang River （Yangtze） estuary （30^.59%, 122^.26＇E） through Taiwan Strait, the South China Sea, and the Eastern Indian Ocean to Prydz Bay, Antarctica （69^.10＇S, 74^.30＇E）, and analyzed them for the 226Ra specific activity. The 226Ra specific activity of the Chanjiang River estuary surface water （3.15 Bq/m3） was found to be the highest among all the surface samples because of the desorption of 226Ra from riverine particles. Between Chanjiang River estuary and 40^.S, 226Ra specific activity was found to be relatively uniform with a mean value of 1.07 Bq/m3 （n= 19, SD=0.14）, similar to that of the open ocean. From 40^.S to 65^.S, 226Ra specific activity increased intensively, then decreased moderately further southwards. Near the Antarctic shore, it increased again, to 2.31 Bq/m3. This distribution was controlled by a combination of deep water upwelling, Southern Ocean fronts, water mixing and the continental 226Ra import. In Prydz Bay and the adjacent sea area, the mean 226Ra activity value was 2.26 Bq/m3 （n=31, SD=0.28）, with a relatively higher value outside of the bay and low 226Ra activity value in the center of the bay. This was consistent with the topography and hydrological setting of the bay. In addition, we extended the study area northward to the Arctic, by combining the published Z26Ra dataset for surface water from the Bering Sea to the Japan Sea. We also discuss the 226Ra distribution of high latitude oceanic surface water and its mechanisms.
文摘目的了解四川省地表水体中^(226)Ra的放射性水平并对其健康风险进行评估。方法于2016年至2021年间检测了四川省主要地表水系23个监测断面的^(226)Ra放射性水平,应用剂量转换系数计算待积有效剂量,应用健康风险模型评估对居民的健康风险。结果四川省地表水体中^(226)Ra的放射性水平为1.9 m Bq/L~20.0m Bq/L,所有地表水体中^(226)Ra的放射性水平均合格;不同年度、不同地表水体的^(226)Ra放射性水平间比较,差异均无统计学意义(P>0.05);平水期地表水体的^(226)Ra放射性水平高于枯水期,差异有统计学意义(P<0.05)。通过饮水、水体浸没途径摄入^(226)Ra而所致年均待积有效剂量在各年龄组均低于0.1 m Sv,对各年龄段居民所致的总致癌风险处于9.50×10^(-9)/a~1.004×10^(-7)/a,均低于WHO和ICRP发布的限值(10^(-6)/a和5×10^(-5)/a)。结论四川省主要地表水系中^(226)Ra的放射性水平均未超标,经直接饮水途径、水体浸没途径摄入^(226)Ra所致健康风险处于可接受水平;全省主要地表水体中^(226)Ra的放射性水平对各年龄组都是安全的。
基金The Scientific Research Foundation of Third Institute of Oceanography,Ministry of Natural Resources under contract No.2020012the Natural Science Foundation of Xiamen,China under contract No.3502Z20227246the Guiding Project of the Science and Technology Plan of Fujian Province under contract No.2020Y0081.
文摘The biogeochemical processes of marine sediments are influenced by bioturbation and organic carbon decomposition,which is crucial for understanding global element cycles and climate change.Two sediment cores were acquired in 2017 from abyssal basins in the central-eastern tropical Pacific to determine the bioturbation and organic carbon degradation processes.The radioactivity concentrations of 210Pb and 226Ra in the sediment cores were measured,indicating the presence of significant excess 210Pb(210Pbex)signals in the sediment cores.Besides,a manganese nodule was discovered in one core,which had a substantial influence on the distribution of 210Pbex.With the exception of this anomalous finding,the bioturbation coefficients in the remaining core were estimated to be 10.6 cm^(2)/a using a steady-state diffusion model,greater than most of the deep-sea sediments from the equatorial eastern Pacific.By using a bio-diffusion model,we further calculated the degradation rates of organic carbon(8.02 ka-1),which is also higher than other areas of the Pacific.Our findings displayed the presence of a biologically active benthic ecosystem in the central-eastern tropical Pacific.
