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 13th (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&...During the 13th (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′S, 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 226Ra 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
Hypoxia is a common phenomenon in the sea adjacent to the Changjiang River Estuary(CJE),one of the global major estuaries.Submarine groundwater discharge(SGD)is a widely recognized pathway for terrestrial materials en...Hypoxia is a common phenomenon in the sea adjacent to the Changjiang River Estuary(CJE),one of the global major estuaries.Submarine groundwater discharge(SGD)is a widely recognized pathway for terrestrial materials entering the sea,and has been found to be significant off the CJE.We used a^(222)Rn mass balance model to estimate the SGD fluxes off the CJE and showed that it is linked to seasonal dissolved oxygen(DO)variations.Average SGD fluxes were estimated to be(0.012±0.010)m^(3)/(m^(2)·d)in winter,(0.034±0.015)m^(3)/(m^(2)·d)in summer,and(0.020±0.010)m^(3)/(m^(2)·d)in autumn.We found a significant negative correlation between DO concentrations and SGD rates with groundwater discharge being highest in the summer flood season.In addition,distribution patterns of SGD and hypoxia zones in summer are spatially overlapped,indicating that SGD is an important contributor to summer hypoxia in this region.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 13th (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′S, 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 226Ra 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.
基金The National Natural Science Foundation of China under contract Nos 42130410 and U22A20580the Fundamental Research Funds for the Central Universities under contract No.202341002.
文摘Hypoxia is a common phenomenon in the sea adjacent to the Changjiang River Estuary(CJE),one of the global major estuaries.Submarine groundwater discharge(SGD)is a widely recognized pathway for terrestrial materials entering the sea,and has been found to be significant off the CJE.We used a^(222)Rn mass balance model to estimate the SGD fluxes off the CJE and showed that it is linked to seasonal dissolved oxygen(DO)variations.Average SGD fluxes were estimated to be(0.012±0.010)m^(3)/(m^(2)·d)in winter,(0.034±0.015)m^(3)/(m^(2)·d)in summer,and(0.020±0.010)m^(3)/(m^(2)·d)in autumn.We found a significant negative correlation between DO concentrations and SGD rates with groundwater discharge being highest in the summer flood season.In addition,distribution patterns of SGD and hypoxia zones in summer are spatially overlapped,indicating that SGD is an important contributor to summer hypoxia in this region.
