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
The based membrane extraction of Th 4+ and Yb 3+ was studied in HBTMPP heptane using a hollow fibber membrane. The separation method of Th 4+ and Yb 3+ was proposed by kinetics competition. The separation operation of...The based membrane extraction of Th 4+ and Yb 3+ was studied in HBTMPP heptane using a hollow fibber membrane. The separation method of Th 4+ and Yb 3+ was proposed by kinetics competition. The separation operation of Th 4+ and Yb 3+ mixture was carried out by two successive extraction and stripping simultaneously. The concentration ratio of Th 4+ to Yb 3+ is 16 74 in the stripping solution. The recovery and purity of Th 4+ are 71 6% and 95 74% respectively.展开更多
This work presents the results of computer simulation of neutronic processes in a high-temperature gas-cooled thorium reactor for 30 different options of core loading.To guarantee stable and long-term reactor operatio...This work presents the results of computer simulation of neutronic processes in a high-temperature gas-cooled thorium reactor for 30 different options of core loading.To guarantee stable and long-term reactor operation(7-10 years),the quantity of fuel compact dispersion phase and starting fuel composition was selected.It is demonstrated that it is possible in principle to substitute the near-axial recirculation zone of the reactor core by a long magnetic trap with a high-temperature plasma column for generating thermonuclear neutrons.The distribution of neutron yield along the length of the plasma source is also presented.Such a thorium reactor,with a near-axial source of extra neutrons,can be applied for researching thermophysical and neutronic characteristics of dispersion thorium fuel to improve its properties.The results of the work are of great interest from the perspective of future advancement of the thermonuclear power industry,by means of creation of a hybrid installation based on a thorium reactor with a long plasma column as a source of additional neutrons.展开更多
Retention behavior of U(VI) and Th(IV) as their 2, 6-pyridine dicarboxylic acid (PDCA) complexes on reversed phase and ion exchange (cation, anion and mixed ion exchange) columns was studied and based on the results, ...Retention behavior of U(VI) and Th(IV) as their 2, 6-pyridine dicarboxylic acid (PDCA) complexes on reversed phase and ion exchange (cation, anion and mixed ion exchange) columns was studied and based on the results, a simple ion chromatography method for the determination of trace level thorium in uranium oxide using 0.075mM 2, 6-pyridine dicarboxylic acid (PDCA) and 1M KNO3 in 1.2M HNO3 as eluent (flow rate 1 mL/min)was proposed. The advantage of the developed method is that the separation of uranium matrix is not required prior to the ion chromatographic determination of trace Th. Separation was carried out on a mixed ion exchange stationary phase and a 10?4 M arsenazo (III) solution was used as post column reagent for detecting the separated metal ions. The separation of Th from uranium using PDCA in the present investigation is attributed through cation exchange mechanism. A calibration plot was constructed by following the standard addition method over the concentration range of 0.25 to 10 ppm of Th in the presence of uranium matrix, which resulted in a linear regression coefficient of 0.9978. The precision of the method was better than 5% and the LOD for Th was found to be 0.1ppm (S/N=3). The method has been validated by comparing the results with the results obtained from ICP-MS analysis where the This separated from the uranium matrix. The proposed method is simple, rapid, accurate and cost effective compared to techniques like ICP-MS or ICP-AES and is suitable for the routine kind of analysis.展开更多
The Bayan Obo deposit in northern China is an ultra-large Fe–REE–Nb deposit.The occurrences,and geochemical characteristics of thorium in iron ores from the Bayan Obo Main Ore Body were examined using chemical analy...The Bayan Obo deposit in northern China is an ultra-large Fe–REE–Nb deposit.The occurrences,and geochemical characteristics of thorium in iron ores from the Bayan Obo Main Ore Body were examined using chemical analysis,field emission scanning electron microscopy,energy dispersive spectrometer,and automatic mineral analysis software.Results identified that 91.69%of ThO2 in the combined samples was mainly distributed in rare earth minerals(bastnaesite,huanghoite,monazite;56.43%abundance in the samples),iron minerals(magnetite,hematite,pyrite;20.97%),niobium minerals(aeschynite;14.29%),and gangue minerals(aegirine,riebeckite,mica,dolomite,apatite,fluorite;4.22%).An unidentified portion(4.09%)of ThO2 may occur in other niobium minerals(niobite,ilmenorutile,pyrochlore).Only a few independent minerals of thorium occur in the iron ore samples.Thorium mainly occurs in rare earth minerals in the form of isomorphic substitution.Analyses of the geochemical characteristics of the major elements indicate that thorium mineralization in the Main Ore Body was related to alkali metasomatism,which provided source material and favorable porosity for hydrothermal mineralization.Trace elements such as Sc,Nb,Zr,and Ta have higher correlation coefficients with thorium,which resulted from being related to the relevant minerals formed during thorium mineralization.In addition,correlation analysis of ThO2 and TFe,and REO and TFe in the six types of iron ore samples showed that ThO2 did not always account for the highest distribution rate in rare earth minerals,and the main occurrence minerals of ThO2 were closely related to iron ore types.展开更多
Density functional theory(DFT) calculations are performed to investigate the electronic and structural properties of the stoichiometric thorium oxide clusters(ThO2)n-/0(n = 1~5). Generalized Koopmans' theorem is a...Density functional theory(DFT) calculations are performed to investigate the electronic and structural properties of the stoichiometric thorium oxide clusters(ThO2)n-/0(n = 1~5). Generalized Koopmans' theorem is applied to predict the vertical detachment energies(VDEs)which are used to simulate the anionic photoelectron spectra(PES). Molecular orbital analyses are performed as well to analyze the chemical bonding in these thorium oxide clusters. The results show that the ground states of(ThO2)_n-/0(n = 1~5) clusters prefer the low-spin structures. With increasing of the cluster size(n), the structure parameters of(ThO2)n-/0(n = 1~5) gradually evolve toward bulk thorium oxide species. It shows that both the coordination number and the average bond length increase gradually in(ThO2)n-/0(n = 1~5) to approach that of ThO2 bulk. What's more, the vibration frequencies of Th=O double bonds are found to be decreasing along with the increased cluster size.展开更多
Herein, we assess the129I transmutation capability of a 2250-MWt single-fluid double-zone thorium molten salt reactor(SD-TMSR) by considering two methods. One is realized by loading an appropriate amount of129I before...Herein, we assess the129I transmutation capability of a 2250-MWt single-fluid double-zone thorium molten salt reactor(SD-TMSR) by considering two methods. One is realized by loading an appropriate amount of129I before the startup of the reactor, and the amount of129I during operation is kept constant by online feeding129I.The other adopts only an initial loading of129I before startup, and no other129I is fed online during operation.The investigation first focuses on the effect of the loading of I on the Th-233U isobreeding performance. The results indicate that a233U isobreeding mode can be achieved for both scenarios for a 60-year operation when the initial molar proportion of LiI is maintained within 0.40% and 0.87%, respectively. Then, the transmutation performances for the two scenarios are compared by changing the amount of injected iodine into the core. It is found that the scenario that adopts an initial loading of129I shows a slightly better transmutation performance in comparison with the scenario that adopts online feeding of129I when the net233U productions for the two scenarios are kept equal. The initial loading of129I scenario with LiI = 0.87% molar proportion is recommended for129I transmutation in the SD-TMSR,and can transmute 1.88 t of129I in the233U isobreeding mode over 60 years.展开更多
Thorium based nuclear fuel is of immense interest to India by virtue of the abundance of Thorium and relative shortage of Uranium. Thorium metal tubes were being cold drawn using copper as cladding to prevent die seiz...Thorium based nuclear fuel is of immense interest to India by virtue of the abundance of Thorium and relative shortage of Uranium. Thorium metal tubes were being cold drawn using copper as cladding to prevent die seizure. After cold drawing, the copper was removed by dissolution in nitric acid. Thorium does not dissolve being passivated by nitric acid. Initially the copper cladding was carried out by inserting copper tubes inside and outside the thorium metal tube. In an innovative development, the mechanical cladding with copper was replaced by electroplated copper with a remarkable improvement in thorium tube acceptance rates. Oxalate derived thoria powder was found to require lower compaction pressures compared to ammonium diuranate derived urania powders to attain the same green compact density. However, the green pellets of thoria were fragile and chipped during handling. The strength improved after introducing a ball milling step before compaction and maintaining the green density above the specified value. Alternatively, binders were used later for greater handling strength. Magnesia was conventionally being used as dopant to enhance the sinterability of thoria. The normal sintering temperature for magnesia doped thoria was 1600℃ - 1700℃, which was achieved in electrically heated molybdenum element sintering furnaces with reducing atmosphere. 0.25 mole percent addition of niobia to the thoria was found to bring down the sintering temperature to 1150℃. Sintering could be done in ordinary furnaces in air atmosphere using silicon carbide or Kanthal heating elements. Electrical conductivity was measured for both magnesia and niobia doped sintered thoria and used in interpreting differences in sintering behavior.展开更多
In this study uranium and thorium contents and depositional characteristics of ay rhan bituminous shales( BS), west of Ankara(central Anatolia), are investigated. Samples used were collected from boreholes opened by P...In this study uranium and thorium contents and depositional characteristics of ay rhan bituminous shales( BS), west of Ankara(central Anatolia), are investigated. Samples used were collected from boreholes opened by Park Holding Ltd. A total of 25 samples were taken from bituminous shale levels in boreholes drilled at 6 different locations in the study area. The H rka formation which hosts bituminous shale deposits is a volcanosedimentary sequence and all lithofacies indicate that a lacustrine environment where the water level was continuously changed. In addition to hydrocarbon generation potential, bituminous shales also accumulate significant amount of radioactive elements such as uranium and thorium. The average uranium and thorium concentrations of BS(1.83/2.62 ppm) are much lower than averages of UC, NASK and PAAS(uranium: 2.70/2.66/3.10 ppm; thorium: 8.50/12.30/14.60 ppm). Low uranium contents in comparison to those of similar lacustrine environments might be attributed to that waters of depositional environment of BS contain low concentration of dissolved uranium and redox conditions were of oxic and dioxic character. Correlation data indicate that U and Th have a similar source and are associated predominantly with clays and phosphates and dominantly with organic material. Radioactive elements in the basin might be derived from Paleozoic granites and metamorphites(e.g. gneiss, schist) which comprise the basement and volcanism which was active in the region throughout the Miocene period. These elements are probably associated with uraniferous phosphate minerals(e.g. autunite, torbernite) which occur in granite, gneiss and schist. BS with average TOC content of 10.96 % shows very good/perfect source rock potential. Positive correlations between Gamma-Ray values and U, Th and K concentrations imply that radioactivity might be originated from these three elements.展开更多
High efficient removal and recovery of uranium and thorium from nuclear waste solution are essential for environmental preservation and fuel recycle. A new polymer fiber adsorbent (UHMEPE-g-PAO fiber), prepared by ami...High efficient removal and recovery of uranium and thorium from nuclear waste solution are essential for environmental preservation and fuel recycle. A new polymer fiber adsorbent (UHMEPE-g-PAO fiber), prepared by amidoximation of grafted polyacrylonitrile onto Ultra High Molecular Weight Polyethylene (UHMWPE) fiber, was used to remove the uranyl and thorium ions from acid aqueous solutions and its performance was carefully investigated. It was found that uranyl ion can penetrate the fiber through the connected pore structures, forming (UO2) (R-C(NH2)-NO)2 chelates with the amidoxime groups within the fiber. Two amidoxime groups (U-N and U-Oeq) and two water molecules (U-Oeq2) are bound to uranyl ion in the fiber. On the contrary, thorium ions are adsorbed mainly on the fiber surface in the form of Th(OH)4 precipitate that blocks the entrance of Th4+ ion into fiber pores. The maximum included other two capacities of uranyl and thorium ions were estimated to be 262.01 mg/g and 160 mg/g at room temperature with pH 3.0, respectively. The results also indicate that the UHMWPE-g-PAO fiber has higher adsorption selectivity for uranyl ion than thorium ion. Uranium and thorium oxide particles were obtained as the ultimate product after sintering of the fiber adsorbent. This novel and environmentally friendly adsorption process is feasible to extract uranium or thorium from acidic aqueous solution.展开更多
We present the thorium distribution on the lunar surface derived from observations by the Chang’E-2 gamma-ray spectrometer(CE-2 GRS). This new map shows a similar thorium distribution to previous observations. In com...We present the thorium distribution on the lunar surface derived from observations by the Chang’E-2 gamma-ray spectrometer(CE-2 GRS). This new map shows a similar thorium distribution to previous observations. In combination with this new thorium map and impact cratering model, we investigate the origination of thorium on the Moon’s highlands, which was previously thought to be contributed from Imbrium ejecta. We found that the Imbrium ejecta has a small contribution(~20%–30%) to the thorium on the lunar highlands but most thorium is likely to be indigenous before the deposition of the Imbrium ejecta. This new thorium map also confirms that the eastern highlands have a relatively higher thorium concentration than the western highlands. We propose that the thin crust and large basins on the eastern highlands are responsible for this difference in thorium.展开更多
Radiopharmaceuticals are used in nuclear medicine for diagnostic or therapeutic acts. The short decay half-lives of medical radioisotopes, especially those used for diagnostics, imply that they should be produced cont...Radiopharmaceuticals are used in nuclear medicine for diagnostic or therapeutic acts. The short decay half-lives of medical radioisotopes, especially those used for diagnostics, imply that they should be produced continuously and transported as quickly as possible to the medical units where they are used. Neutron-rich medical radioisotopes are generally produced in research reactors, like technetium-99m, lutetium-177, holmium-166 and iodine-131. On the other hand, proton-rich radioisotopes are produced via reactions with charged particles from accelerators like fluorine-18, gallium-67, iodine-123 and thallium-201. Beside this, innovative nuclear reactors are advocated as solutions to the issues of nuclear waste production and proliferation threats. Fast neutron, thorium-cycle and accelerator-driven subcritical (ADS) reactors are some of the most promising of them, proposed as safer fuel breeders and “waste burners”. This article examines the use of a fast thorium-cycle ADS with liquid lead-bismuth eutectic coolant for the production of molybdenum-99/technetium-99m and lutetium-177. Burnup simulation has been made with the Monte-Carlo (MC) code SERPENT. It is demonstrated that MC codes can advantageously be used to determine the optimal irradiation time for a given radioisotope in a realistic reactor core. It is also shown that fast thorium-cycle ADS is an economical option for the production of medical radioisotopes.展开更多
Axial gas-liquid separators have been adopted in fission gas removal systems for the development of thorium molten salt reactors. In our previous study, we observed an unsteady flow phenomenon in which the flow patter...Axial gas-liquid separators have been adopted in fission gas removal systems for the development of thorium molten salt reactors. In our previous study, we observed an unsteady flow phenomenon in which the flow pattern is directly dependent on the backpressure in a gas-liquid separator; however, the underlying flow mechanism is still unknown. In order to move a step further in clarifying how the flow pattern evolves with a variation in backpressure, a large eddy simulation(LES) was adopted to study the flow field evolution. In the simulation, an artificial boundary was applied at the separator outlet under the assumption that the backpressure increases linearly. The numerical results indicate that the unsteady flow feature is captured by the LES approach, and the flow transition is mainly due to the axial velocity profile redistribution induced by the backpressure variation. With the increase in backpressure,the axial velocity near the downstream orifice transits from negative to positive. This change in the axial velocity sign forces the unstable spiral vortex to become a stable rectilinear vortex.展开更多
The advantages of once-through molten salt reactors include readily available fuel,low nuclear proliferation risk,and low technical difficulty.It is potentially the most easily commercialized fuel cycle mode for molte...The advantages of once-through molten salt reactors include readily available fuel,low nuclear proliferation risk,and low technical difficulty.It is potentially the most easily commercialized fuel cycle mode for molten salt reactors.However,there are some problems in the parameter selection of once-through molten salt reactors,and the relevant burnup optimization work requires further analysis.This study examined once-through graphitemoderated molten salt reactor using enriched uranium and thorium.The fuel volume fraction(VF),initial heavy nuclei concentration(HN_(0)),feeding uranium enrichment(E_(FU)),volume of the reactor core,and fuel type were changed to obtain the optimal conditions for burnup.We found an optimal region for VF and HN_(0) in each scheme,and the location and size of the optimal region changed with the degree of E_(FU),core volume,and fuel type.The recommended core schemes provide a reference for the core design of a once-through molten salt reactor.展开更多
Supercritical Fluid Extraction (SFE) is emerging as a powerful technique in the extraction of metal ions. In the present study, the extraction of nitrates of uranium and thorium was carried out using supercritical car...Supercritical Fluid Extraction (SFE) is emerging as a powerful technique in the extraction of metal ions. In the present study, the extraction of nitrates of uranium and thorium was carried out using supercritical carbon dioxide (Sc-CO2) modified with various organophosphorous compounds such as dialkylalkyl phosphonates, trialkyl phosphates and trialkyl phosphine oxides in the presence of co-solvents such as methanol, dichlormethane and n-hexane. The influence of ligand and co-solvent on the extraction of the metal nitrates was studied in detail. These studies have established that co-solvent plays an important role in the extraction as well as fractionation of uranium and thorium nitrates. Polar co-solvent, methanol provided faster extraction without fractionation whereas the non-polar solvent, e.g. n-hexane provided some fractionation of metal nitrates though the extraction kinetics was slower.展开更多
During recent years, a new generation of nuclear reactors, known as “Accelerator Driven Subcritical Reactors”, has been developed. One of the new application aspects for such reactors (besides transmutation of High ...During recent years, a new generation of nuclear reactors, known as “Accelerator Driven Subcritical Reactors”, has been developed. One of the new application aspects for such reactors (besides transmutation of High Level Waste and burning Minor Actinides) is usage of thorium as nuclear fuel. In this work a subcritical core in experimental scale is simulated by MCNPX code. The core contains two types of fuel assemblies: (85% ThO2 + 15% UO2) and MOX (U-Pu). In the first step, only the thorium-contained fuel assemblies are loaded into the core. Criticality calculations using MCNPX show that the keff is so low that the fuel assemblies cannot run the subcritical core. This implies that MOX (U-Pu) assemblies must be loaded as well. Neutronic parameters of the thorium- fueled Accelerator Driven Subcritical core are then calculated as well as some other parameters related to accelerator coupled with the core. The main objective of this simulation is to study the behavior of Accelerator Driven Subcritical core with thorium assemblies.展开更多
The existence of the thorium element in the ores from the Atacama region, Chile, and its importance in the activities of the nuclear industry, have generated the interest of the Chilean Nuclear Energy Commission (CChE...The existence of the thorium element in the ores from the Atacama region, Chile, and its importance in the activities of the nuclear industry, have generated the interest of the Chilean Nuclear Energy Commission (CChEN) to study the technical feasibility of its recovery, like ThO2 through the implementation of hydrometallurgical techniques, such as leaching, solvent extraction, among others. The present work has become a report about the research carried out in the Extractive Metallurgy Area of the Department of Advanced Materials of CChEN, whose objective is to know the behavior of the thorium element when the mineral carrier is leached. The leaching tests were carried out in a glass reactor in batch mode, by mechanical agitation, varying different operational parameters, such as: type of leaching solution, concentration of acid in the solution, system temperature and granulometry of the mineral. The results indicate that there is technical feasibility for the recovery of thorium by leaching the mineral carrier with hydrochloric and/or sulfuric solution. The highest recovery of thorium for a sulfuric solution was 70.0% and for a hydrochloric solution of 83.8%, so the process presents a good efficiency in both cases. For a hydrochloric solution, the mathematical model of the thorium recovery efficiency obtained is: Y=31.14+26.25*X1+8.69*X2−0.82*X3+9.5*X12−0.83*X13−3.71*X23−1.83*X123+6.45 The concentration of HCl and temperature, as well as their interaction, significantly affect the recovery of thorium for Sierra Indiana mineral, as well as temperature and granulometry. The previous model gives a good representativeness of 99.98%. For a sulfuric solution, the mathematical model of the thorium recovery efficiency obtained is: Y=29.78+25.92*X1+0.99*X2−1.05*X3−2.05*X12−9.84*X13−5.26*X23−3.87*X123+15.18 The model indicates that the recovery of thorium for the mineral is significantly affected by the concentration of sulfuric acid, and to a lesser degree by the temperature and granulometry. The model provides a representativeness of 98.3%.展开更多
Th(BrO3)3·H2O single crystals were grown from its aqueous solution at room temperature. Single crystal XRD, Raman and FTIR techniques were used to investigate the crystal structure. The crystal structure was solv...Th(BrO3)3·H2O single crystals were grown from its aqueous solution at room temperature. Single crystal XRD, Raman and FTIR techniques were used to investigate the crystal structure. The crystal structure was solved by Patterson method. The as grown crystals are in monoclinic system with space group P21/c. The unit cell parameters are a = 12.8555(18) ?, b = 7.8970(11) ?, c = 9.0716(10)?, α = 90°, β = 131.568° and γ = 90° and unit cell volume is 689.1(2)?3. Z = 8, R factor is 5.9. The Raman and FTIR studies indicate the lowering of symetry of bromate anion from C3V to C1. Hydrogen bonds with varying strengths are present in the crystal. The centrosymmetric space group P21/c of the crystal is confirmed by the non-coincidence of majority of Raman and IR bands.展开更多
The purpose of the paper is to study the performance of the CANDU(Canada Deuterium Uranium)reactor when the reactor core is loaded with thorium fuel mixed with plutonium isotopes with ratio 3 and 5%.A three dimensiona...The purpose of the paper is to study the performance of the CANDU(Canada Deuterium Uranium)reactor when the reactor core is loaded with thorium fuel mixed with plutonium isotopes with ratio 3 and 5%.A three dimensional model is designed for the core of CANDU reactor.The computer code MCNPX(Monte Carlo N–Particle Transport)is used to calculate the processes in its core.The results are compared with natural UO2 case which is the typical fuel of the reactor.The results show that the multiplication factor of the reactor is higher even in the case of thorium fuel mixed with 3%plutonium isotopes,which indicates longer neutron life cycle length and more economic utilization of the reactor.展开更多
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The based membrane extraction of Th 4+ and Yb 3+ was studied in HBTMPP heptane using a hollow fibber membrane. The separation method of Th 4+ and Yb 3+ was proposed by kinetics competition. The separation operation of Th 4+ and Yb 3+ mixture was carried out by two successive extraction and stripping simultaneously. The concentration ratio of Th 4+ to Yb 3+ is 16 74 in the stripping solution. The recovery and purity of Th 4+ are 71 6% and 95 74% respectively.
文摘This work presents the results of computer simulation of neutronic processes in a high-temperature gas-cooled thorium reactor for 30 different options of core loading.To guarantee stable and long-term reactor operation(7-10 years),the quantity of fuel compact dispersion phase and starting fuel composition was selected.It is demonstrated that it is possible in principle to substitute the near-axial recirculation zone of the reactor core by a long magnetic trap with a high-temperature plasma column for generating thermonuclear neutrons.The distribution of neutron yield along the length of the plasma source is also presented.Such a thorium reactor,with a near-axial source of extra neutrons,can be applied for researching thermophysical and neutronic characteristics of dispersion thorium fuel to improve its properties.The results of the work are of great interest from the perspective of future advancement of the thermonuclear power industry,by means of creation of a hybrid installation based on a thorium reactor with a long plasma column as a source of additional neutrons.
文摘Retention behavior of U(VI) and Th(IV) as their 2, 6-pyridine dicarboxylic acid (PDCA) complexes on reversed phase and ion exchange (cation, anion and mixed ion exchange) columns was studied and based on the results, a simple ion chromatography method for the determination of trace level thorium in uranium oxide using 0.075mM 2, 6-pyridine dicarboxylic acid (PDCA) and 1M KNO3 in 1.2M HNO3 as eluent (flow rate 1 mL/min)was proposed. The advantage of the developed method is that the separation of uranium matrix is not required prior to the ion chromatographic determination of trace Th. Separation was carried out on a mixed ion exchange stationary phase and a 10?4 M arsenazo (III) solution was used as post column reagent for detecting the separated metal ions. The separation of Th from uranium using PDCA in the present investigation is attributed through cation exchange mechanism. A calibration plot was constructed by following the standard addition method over the concentration range of 0.25 to 10 ppm of Th in the presence of uranium matrix, which resulted in a linear regression coefficient of 0.9978. The precision of the method was better than 5% and the LOD for Th was found to be 0.1ppm (S/N=3). The method has been validated by comparing the results with the results obtained from ICP-MS analysis where the This separated from the uranium matrix. The proposed method is simple, rapid, accurate and cost effective compared to techniques like ICP-MS or ICP-AES and is suitable for the routine kind of analysis.
基金supported by the National Basic Research Program of China (973 Program) (2012CBA01200)Northern Rare Earth Science and Technology Project (BFXT-2015D-0002) and (2016H1928)
文摘The Bayan Obo deposit in northern China is an ultra-large Fe–REE–Nb deposit.The occurrences,and geochemical characteristics of thorium in iron ores from the Bayan Obo Main Ore Body were examined using chemical analysis,field emission scanning electron microscopy,energy dispersive spectrometer,and automatic mineral analysis software.Results identified that 91.69%of ThO2 in the combined samples was mainly distributed in rare earth minerals(bastnaesite,huanghoite,monazite;56.43%abundance in the samples),iron minerals(magnetite,hematite,pyrite;20.97%),niobium minerals(aeschynite;14.29%),and gangue minerals(aegirine,riebeckite,mica,dolomite,apatite,fluorite;4.22%).An unidentified portion(4.09%)of ThO2 may occur in other niobium minerals(niobite,ilmenorutile,pyrochlore).Only a few independent minerals of thorium occur in the iron ore samples.Thorium mainly occurs in rare earth minerals in the form of isomorphic substitution.Analyses of the geochemical characteristics of the major elements indicate that thorium mineralization in the Main Ore Body was related to alkali metasomatism,which provided source material and favorable porosity for hydrothermal mineralization.Trace elements such as Sc,Nb,Zr,and Ta have higher correlation coefficients with thorium,which resulted from being related to the relevant minerals formed during thorium mineralization.In addition,correlation analysis of ThO2 and TFe,and REO and TFe in the six types of iron ore samples showed that ThO2 did not always account for the highest distribution rate in rare earth minerals,and the main occurrence minerals of ThO2 were closely related to iron ore types.
基金supported by Hunan Police Academy Research Innovation Team-Key Technologies of Road Traffic Safety Law Enforcementthe Key Laboratory of Impression Evidence Examination and Identification Technology,Ministry of Public Security,People’s Republic of China
文摘Density functional theory(DFT) calculations are performed to investigate the electronic and structural properties of the stoichiometric thorium oxide clusters(ThO2)n-/0(n = 1~5). Generalized Koopmans' theorem is applied to predict the vertical detachment energies(VDEs)which are used to simulate the anionic photoelectron spectra(PES). Molecular orbital analyses are performed as well to analyze the chemical bonding in these thorium oxide clusters. The results show that the ground states of(ThO2)_n-/0(n = 1~5) clusters prefer the low-spin structures. With increasing of the cluster size(n), the structure parameters of(ThO2)n-/0(n = 1~5) gradually evolve toward bulk thorium oxide species. It shows that both the coordination number and the average bond length increase gradually in(ThO2)n-/0(n = 1~5) to approach that of ThO2 bulk. What's more, the vibration frequencies of Th=O double bonds are found to be decreasing along with the increased cluster size.
基金supported by the Chinese TMSR Strategic Pioneer Science and Technology Project(No.XDA02010000)the Frontier Science Key Program of the Chinese Academy of Sciences(No.QYZDY-SSW-JSC016)
文摘Herein, we assess the129I transmutation capability of a 2250-MWt single-fluid double-zone thorium molten salt reactor(SD-TMSR) by considering two methods. One is realized by loading an appropriate amount of129I before the startup of the reactor, and the amount of129I during operation is kept constant by online feeding129I.The other adopts only an initial loading of129I before startup, and no other129I is fed online during operation.The investigation first focuses on the effect of the loading of I on the Th-233U isobreeding performance. The results indicate that a233U isobreeding mode can be achieved for both scenarios for a 60-year operation when the initial molar proportion of LiI is maintained within 0.40% and 0.87%, respectively. Then, the transmutation performances for the two scenarios are compared by changing the amount of injected iodine into the core. It is found that the scenario that adopts an initial loading of129I shows a slightly better transmutation performance in comparison with the scenario that adopts online feeding of129I when the net233U productions for the two scenarios are kept equal. The initial loading of129I scenario with LiI = 0.87% molar proportion is recommended for129I transmutation in the SD-TMSR,and can transmute 1.88 t of129I in the233U isobreeding mode over 60 years.
文摘Thorium based nuclear fuel is of immense interest to India by virtue of the abundance of Thorium and relative shortage of Uranium. Thorium metal tubes were being cold drawn using copper as cladding to prevent die seizure. After cold drawing, the copper was removed by dissolution in nitric acid. Thorium does not dissolve being passivated by nitric acid. Initially the copper cladding was carried out by inserting copper tubes inside and outside the thorium metal tube. In an innovative development, the mechanical cladding with copper was replaced by electroplated copper with a remarkable improvement in thorium tube acceptance rates. Oxalate derived thoria powder was found to require lower compaction pressures compared to ammonium diuranate derived urania powders to attain the same green compact density. However, the green pellets of thoria were fragile and chipped during handling. The strength improved after introducing a ball milling step before compaction and maintaining the green density above the specified value. Alternatively, binders were used later for greater handling strength. Magnesia was conventionally being used as dopant to enhance the sinterability of thoria. The normal sintering temperature for magnesia doped thoria was 1600℃ - 1700℃, which was achieved in electrically heated molybdenum element sintering furnaces with reducing atmosphere. 0.25 mole percent addition of niobia to the thoria was found to bring down the sintering temperature to 1150℃. Sintering could be done in ordinary furnaces in air atmosphere using silicon carbide or Kanthal heating elements. Electrical conductivity was measured for both magnesia and niobia doped sintered thoria and used in interpreting differences in sintering behavior.
基金supported by Ankara University Scientific Research Projects Coordination Unit(Project No:09B4343013)
文摘In this study uranium and thorium contents and depositional characteristics of ay rhan bituminous shales( BS), west of Ankara(central Anatolia), are investigated. Samples used were collected from boreholes opened by Park Holding Ltd. A total of 25 samples were taken from bituminous shale levels in boreholes drilled at 6 different locations in the study area. The H rka formation which hosts bituminous shale deposits is a volcanosedimentary sequence and all lithofacies indicate that a lacustrine environment where the water level was continuously changed. In addition to hydrocarbon generation potential, bituminous shales also accumulate significant amount of radioactive elements such as uranium and thorium. The average uranium and thorium concentrations of BS(1.83/2.62 ppm) are much lower than averages of UC, NASK and PAAS(uranium: 2.70/2.66/3.10 ppm; thorium: 8.50/12.30/14.60 ppm). Low uranium contents in comparison to those of similar lacustrine environments might be attributed to that waters of depositional environment of BS contain low concentration of dissolved uranium and redox conditions were of oxic and dioxic character. Correlation data indicate that U and Th have a similar source and are associated predominantly with clays and phosphates and dominantly with organic material. Radioactive elements in the basin might be derived from Paleozoic granites and metamorphites(e.g. gneiss, schist) which comprise the basement and volcanism which was active in the region throughout the Miocene period. These elements are probably associated with uraniferous phosphate minerals(e.g. autunite, torbernite) which occur in granite, gneiss and schist. BS with average TOC content of 10.96 % shows very good/perfect source rock potential. Positive correlations between Gamma-Ray values and U, Th and K concentrations imply that radioactivity might be originated from these three elements.
文摘High efficient removal and recovery of uranium and thorium from nuclear waste solution are essential for environmental preservation and fuel recycle. A new polymer fiber adsorbent (UHMEPE-g-PAO fiber), prepared by amidoximation of grafted polyacrylonitrile onto Ultra High Molecular Weight Polyethylene (UHMWPE) fiber, was used to remove the uranyl and thorium ions from acid aqueous solutions and its performance was carefully investigated. It was found that uranyl ion can penetrate the fiber through the connected pore structures, forming (UO2) (R-C(NH2)-NO)2 chelates with the amidoxime groups within the fiber. Two amidoxime groups (U-N and U-Oeq) and two water molecules (U-Oeq2) are bound to uranyl ion in the fiber. On the contrary, thorium ions are adsorbed mainly on the fiber surface in the form of Th(OH)4 precipitate that blocks the entrance of Th4+ ion into fiber pores. The maximum included other two capacities of uranyl and thorium ions were estimated to be 262.01 mg/g and 160 mg/g at room temperature with pH 3.0, respectively. The results also indicate that the UHMWPE-g-PAO fiber has higher adsorption selectivity for uranyl ion than thorium ion. Uranium and thorium oxide particles were obtained as the ultimate product after sintering of the fiber adsorbent. This novel and environmentally friendly adsorption process is feasible to extract uranium or thorium from acidic aqueous solution.
基金supported by the National Natural Science Foundation of China(11773087)the Science and Technology Development Fund of Macao(079/2018/A2)
文摘We present the thorium distribution on the lunar surface derived from observations by the Chang’E-2 gamma-ray spectrometer(CE-2 GRS). This new map shows a similar thorium distribution to previous observations. In combination with this new thorium map and impact cratering model, we investigate the origination of thorium on the Moon’s highlands, which was previously thought to be contributed from Imbrium ejecta. We found that the Imbrium ejecta has a small contribution(~20%–30%) to the thorium on the lunar highlands but most thorium is likely to be indigenous before the deposition of the Imbrium ejecta. This new thorium map also confirms that the eastern highlands have a relatively higher thorium concentration than the western highlands. We propose that the thin crust and large basins on the eastern highlands are responsible for this difference in thorium.
文摘Radiopharmaceuticals are used in nuclear medicine for diagnostic or therapeutic acts. The short decay half-lives of medical radioisotopes, especially those used for diagnostics, imply that they should be produced continuously and transported as quickly as possible to the medical units where they are used. Neutron-rich medical radioisotopes are generally produced in research reactors, like technetium-99m, lutetium-177, holmium-166 and iodine-131. On the other hand, proton-rich radioisotopes are produced via reactions with charged particles from accelerators like fluorine-18, gallium-67, iodine-123 and thallium-201. Beside this, innovative nuclear reactors are advocated as solutions to the issues of nuclear waste production and proliferation threats. Fast neutron, thorium-cycle and accelerator-driven subcritical (ADS) reactors are some of the most promising of them, proposed as safer fuel breeders and “waste burners”. This article examines the use of a fast thorium-cycle ADS with liquid lead-bismuth eutectic coolant for the production of molybdenum-99/technetium-99m and lutetium-177. Burnup simulation has been made with the Monte-Carlo (MC) code SERPENT. It is demonstrated that MC codes can advantageously be used to determine the optimal irradiation time for a given radioisotope in a realistic reactor core. It is also shown that fast thorium-cycle ADS is an economical option for the production of medical radioisotopes.
基金supported by the National Natural Science Foundation of China(Nos.11535009 and 51406114)
文摘Axial gas-liquid separators have been adopted in fission gas removal systems for the development of thorium molten salt reactors. In our previous study, we observed an unsteady flow phenomenon in which the flow pattern is directly dependent on the backpressure in a gas-liquid separator; however, the underlying flow mechanism is still unknown. In order to move a step further in clarifying how the flow pattern evolves with a variation in backpressure, a large eddy simulation(LES) was adopted to study the flow field evolution. In the simulation, an artificial boundary was applied at the separator outlet under the assumption that the backpressure increases linearly. The numerical results indicate that the unsteady flow feature is captured by the LES approach, and the flow transition is mainly due to the axial velocity profile redistribution induced by the backpressure variation. With the increase in backpressure,the axial velocity near the downstream orifice transits from negative to positive. This change in the axial velocity sign forces the unstable spiral vortex to become a stable rectilinear vortex.
基金supported by the Shanghai Sailing Program(No.19YF1457900)Chinese TMSR Strategic Pioneer Science and Technology Project(No.XDA02010000)+1 种基金National Natural Science Foundation of China(No.12005290)Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2020261)。
文摘The advantages of once-through molten salt reactors include readily available fuel,low nuclear proliferation risk,and low technical difficulty.It is potentially the most easily commercialized fuel cycle mode for molten salt reactors.However,there are some problems in the parameter selection of once-through molten salt reactors,and the relevant burnup optimization work requires further analysis.This study examined once-through graphitemoderated molten salt reactor using enriched uranium and thorium.The fuel volume fraction(VF),initial heavy nuclei concentration(HN_(0)),feeding uranium enrichment(E_(FU)),volume of the reactor core,and fuel type were changed to obtain the optimal conditions for burnup.We found an optimal region for VF and HN_(0) in each scheme,and the location and size of the optimal region changed with the degree of E_(FU),core volume,and fuel type.The recommended core schemes provide a reference for the core design of a once-through molten salt reactor.
文摘Supercritical Fluid Extraction (SFE) is emerging as a powerful technique in the extraction of metal ions. In the present study, the extraction of nitrates of uranium and thorium was carried out using supercritical carbon dioxide (Sc-CO2) modified with various organophosphorous compounds such as dialkylalkyl phosphonates, trialkyl phosphates and trialkyl phosphine oxides in the presence of co-solvents such as methanol, dichlormethane and n-hexane. The influence of ligand and co-solvent on the extraction of the metal nitrates was studied in detail. These studies have established that co-solvent plays an important role in the extraction as well as fractionation of uranium and thorium nitrates. Polar co-solvent, methanol provided faster extraction without fractionation whereas the non-polar solvent, e.g. n-hexane provided some fractionation of metal nitrates though the extraction kinetics was slower.
文摘During recent years, a new generation of nuclear reactors, known as “Accelerator Driven Subcritical Reactors”, has been developed. One of the new application aspects for such reactors (besides transmutation of High Level Waste and burning Minor Actinides) is usage of thorium as nuclear fuel. In this work a subcritical core in experimental scale is simulated by MCNPX code. The core contains two types of fuel assemblies: (85% ThO2 + 15% UO2) and MOX (U-Pu). In the first step, only the thorium-contained fuel assemblies are loaded into the core. Criticality calculations using MCNPX show that the keff is so low that the fuel assemblies cannot run the subcritical core. This implies that MOX (U-Pu) assemblies must be loaded as well. Neutronic parameters of the thorium- fueled Accelerator Driven Subcritical core are then calculated as well as some other parameters related to accelerator coupled with the core. The main objective of this simulation is to study the behavior of Accelerator Driven Subcritical core with thorium assemblies.
文摘The existence of the thorium element in the ores from the Atacama region, Chile, and its importance in the activities of the nuclear industry, have generated the interest of the Chilean Nuclear Energy Commission (CChEN) to study the technical feasibility of its recovery, like ThO2 through the implementation of hydrometallurgical techniques, such as leaching, solvent extraction, among others. The present work has become a report about the research carried out in the Extractive Metallurgy Area of the Department of Advanced Materials of CChEN, whose objective is to know the behavior of the thorium element when the mineral carrier is leached. The leaching tests were carried out in a glass reactor in batch mode, by mechanical agitation, varying different operational parameters, such as: type of leaching solution, concentration of acid in the solution, system temperature and granulometry of the mineral. The results indicate that there is technical feasibility for the recovery of thorium by leaching the mineral carrier with hydrochloric and/or sulfuric solution. The highest recovery of thorium for a sulfuric solution was 70.0% and for a hydrochloric solution of 83.8%, so the process presents a good efficiency in both cases. For a hydrochloric solution, the mathematical model of the thorium recovery efficiency obtained is: Y=31.14+26.25*X1+8.69*X2−0.82*X3+9.5*X12−0.83*X13−3.71*X23−1.83*X123+6.45 The concentration of HCl and temperature, as well as their interaction, significantly affect the recovery of thorium for Sierra Indiana mineral, as well as temperature and granulometry. The previous model gives a good representativeness of 99.98%. For a sulfuric solution, the mathematical model of the thorium recovery efficiency obtained is: Y=29.78+25.92*X1+0.99*X2−1.05*X3−2.05*X12−9.84*X13−5.26*X23−3.87*X123+15.18 The model indicates that the recovery of thorium for the mineral is significantly affected by the concentration of sulfuric acid, and to a lesser degree by the temperature and granulometry. The model provides a representativeness of 98.3%.
文摘Th(BrO3)3·H2O single crystals were grown from its aqueous solution at room temperature. Single crystal XRD, Raman and FTIR techniques were used to investigate the crystal structure. The crystal structure was solved by Patterson method. The as grown crystals are in monoclinic system with space group P21/c. The unit cell parameters are a = 12.8555(18) ?, b = 7.8970(11) ?, c = 9.0716(10)?, α = 90°, β = 131.568° and γ = 90° and unit cell volume is 689.1(2)?3. Z = 8, R factor is 5.9. The Raman and FTIR studies indicate the lowering of symetry of bromate anion from C3V to C1. Hydrogen bonds with varying strengths are present in the crystal. The centrosymmetric space group P21/c of the crystal is confirmed by the non-coincidence of majority of Raman and IR bands.
文摘The purpose of the paper is to study the performance of the CANDU(Canada Deuterium Uranium)reactor when the reactor core is loaded with thorium fuel mixed with plutonium isotopes with ratio 3 and 5%.A three dimensional model is designed for the core of CANDU reactor.The computer code MCNPX(Monte Carlo N–Particle Transport)is used to calculate the processes in its core.The results are compared with natural UO2 case which is the typical fuel of the reactor.The results show that the multiplication factor of the reactor is higher even in the case of thorium fuel mixed with 3%plutonium isotopes,which indicates longer neutron life cycle length and more economic utilization of the reactor.
