最新刊期
卷 0 ， 期 0 ， 2020
- 摘要：Background:Synchrotron radiation(SR) has some unique features such as higher brightness and continuously adjustable wavelength.Sometimes SR source will be a unique choice in some experiments.And with the development of the SR facility,especially the appearance of various low emittance undulators,the experiments such as coherent diffraction imaging(CDI) that needs high brightness coherence source can be conducted.The traditional ray trace software,such as Shadow,using the geometrical optics methods,could not be applied for the coherent beamlines.Purpose:We want to provide a basis for the beamline design and the X-ray coherent experiments,the effective evaluation of the spatial coherence in beamlines is needed.Undulator source,which can be calculated precisely,will become a plane source with some features.As the source of the beamline,undulator was calculated.And the spatial coherence of the exit slit can be calculated too.So we can analyze the coherence of the beamline.Methods:Firstly,we used BPM to measure the intensity of the diffraction of the slit,and simulated the intensity distribution of the slit diffraction using the MCI(a software written by ourselves) to confirm the coherent length of the secondary source at slit.Secondly,we calculated the undulator supposed as a plane source,and used the MCI to numerically calculate the propagation of partially coherent X-ray in the soft X-ray interference lithography beamline from the undulator to the exit slit.Finally,we compared the difference of the coherent length at the slit by the above two methods.Results:We calculated the coherent length at the different place in the beamline,such as mirrors and slits.The most important thing was that we could not only know the coherent length with different size of the slits,but also control the spatial coherence quantitatively.When the slit size was 40 m×40 m,the spatial coherence was almost fully coherent.And we used the method to do some simulation about the coherent experiments and the coherent beamline design.Conclusions:The new method was available for the coherence analysis of the beamline.The calculation of the undulator was proper.And the quantitative analysis and control of spatial coherence could provide a basis for the X-ray coherent experiments and the coherent beamline design.关键词：X-ray optics;Spatial coherence;Undulator;Coherent length
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发布时间：2021-03-05 - 摘要：Background:Measuring trace elements in tea can determine its nutritional value,verify the authenticity and place of origin,and detect the poisonous and harmful elements remaining in tea due to the application of chemical fertilizers and pesticides.Purpose:In order to reduce the time for sample preparation and the costs of equipment maintenance,wavelength dispersive X-ray fluorescence(WDXRF) spectroscopy was used to determine the trace elements in tea which is rapid,non-destructive and accurate.The contents of more than 20 elements can be measured simultaneously.Methods:Sample pieces were made by the sample preparation method of boric acid rebasing.To avoid the exogenous environmental pollution subjected in the growth of tea,we removed the residual dust of the tea by cleaning it.According to the principle that the standard samples should be similar types with the samples to be analyzed to select standard samples.The curves were built by SuperQ,which contained compiling the measurement conditions,establishing the measurement conditions,checking the angles,determining the measurement times,checking PHD and adding the contents and the names of sample pieces.The accuracy of the method can be obtained by comparing the measured values with the trace element contents of standard samples.The contents of trace elements in tea determined by WDXRF can be used to classify the tea attribution and the tea species through cluster analysis of SPSS software.Results:(1) The results show that the biggest relative standard deviation is 0.43% of Pb,and the precision is very good.(2) Five kinds of tea are taken separately in Fujian and Yunnan,measured three times with the established working curves.And tree diagram of cluster analysis can be obtained with SPSS software to analyze the measured average values with cluster analysis,coupling method between groups and Minkowski distance measurement techniques.It can be seen that in the tree diagram,when the critical value λ was 15,the tea samples were divided into two categories.Y1 to Y5 were Yunnan tea samples and F1 to F4 were Fujian tea samples.Four kinds of black tea,any three kinds of green tea and a kind of jasmine tea are taken in Yunnan,measured three times with the established working curves.And tree diagram of cluster analysis can also be obtained.Cluster analysis showed that,black tea and green tea can be classified significantly based on the contents of mineral elements in tea.Conclusions:Compared with AAS and ICP-OES,WDXRF is a small-costing,short-consuming and simple-process method.关键词：Wavelength dispersive X-ray fluorescence spectroscopy(WDXRF);Tea;Content of trace elements;SPSS;Attributions of tea;Types of tea
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发布时间：2021-03-05 - 摘要：Background:Hydrogen-water catalytic exchange reaction offers an approach to hydrogen isotope separation,which can be applied in heavy water detritiation.Purpose:To optimize the operating condition for hydrogen-water catalytic exchange reaction,we analysed the influence of different factors on the transfer coefficient.Methods:In detail,the isotope exchange experiments of H-D system were carried out in a self-designed catalytic bed loaded with hydrophobic catalyst and hydrophilic packing with certain volume ratio.The experiments showed the changes of both the transfer coefficient and the pressure drop of column with the changing of the operational temperatures(29°C,45°C,60°C and 75°C),the ratios of gas to liquid(0.58,1.17,2.65,3.54) and the deuterium concentrations(5.05×10 3,1.0144×10 2,2.01×10 2).Results:Results showed that 45°C is the optimal temperature for operating.The transfer coefficient increases with the increasinng of the ratio of gas to liquid in the ranges of 0.58to 1.17 and 2.65 to 3.56,while decreases with the deuterium concentration increases from 5.05×10 3to 2.01×10 2.The pressure drop of column increases with increasing of gas flow rate.Conclusions:The experiment proves that the ratio of gas to liquid,the reaction temperature and the deuterium concentration are all important factors,which influence the transfer coefficient of deuterium obviously.The optimal operating condition for hydrogen-water catalytic exchange reaction are as follows:the temperature is 45°C,the ratio of gas to liquid is 3.56,and the deuterium concentration is 2.01×10 2.关键词：Catalytic exchange;Hydrophobic catalyst;Transfer coefficient;Pressure drop of column
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发布时间：2021-03-05 - 摘要：Background:7Li(p,n) reaction of high neutron yield and low threshold energy has become one of the most important neutron generating reactions for Accelerator-based Boron Neutron Capture Therapy(BNCT).Purpose:Focuses on neutron yield and spectrum characteristics of this kind of neutron generating reaction which serves as an accelerator-based neutron source and moderates the high energy neutron beams to meet BNCT requirements.Methods:The yield and energy spectrum of neutrons generated by accelerator-based7Li(p,n) reaction with incident proton energy from 1.9 MeV to 3.0 MeV are researched using the Monte Carlo code-MCNPX2.5.0.And the energy and angular distribution of differential neutron yield by 2.5-MeV incident proton are also given in this part.In the following part,the character of epithermal neutron beam generated by 2.5-MeV incident protons is moderated by a new-designed moderator.Results:Energy spectra of neutrons generated by accelerator-based7Li(p,n) reaction with incident proton energy from 1.9 MeV to 3.0 MeV are got through the simulation and calculation.The best moderator thickness is got through comparison.Conclusions:Neutron beam produced by accelerator-based7Li(p,n) reaction,with the bombarding beam of 10 mA and the energy of 2.5 MeV,can meet the requirement of BNCT well after being moderated.关键词：Boron neutron capture therapy;Monte Carlo method;Epithermal neutron;Neutron moderator
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发布时间：2021-03-05 - 摘要：Background:In the nuclear disarmament process,the measurement and verification of uranium casting in sealed container are important to process control and treaty implementation.It is a difficult and hot problem to verify uranium casting in a sealed metal container,due to the weak intensity of neutron and γ rays of uranium.Purpose:We want to measure the correlation functions of different casting in uranium casting verifications.Methods:Two BC501 scintillation detectors are placed outside the tagged neutron cone and in opposite position.The α detector forms the first channel pulse signal,while the two BC501 scintillation detectors form the second and third channel pulse signals.Those three pulsed time series are recorded by high speed acquisition system.The correlation functions between these signals are calculated by the time series.Results:Putting the two BC501 detectors into the tagged neutron cone,the time of flight for the 14-MeV neutron is measured.The FWHM in TOF spectrum is 2.0 ns.Putting the two BC501 detectors outside the tagged neutron cone,the correlation functions measured by high speed acquisition system and MCA are consistent.The spontaneous neutron decay constants of the castings are measured byγ rays.The decay constant of 6.5-kg Pb component is 184 μs 1.The decay constants of 4-kg and 15-kg HEU casting are 210 μs 1and 128 μs 1,respectively.The correlation functions C12(τ),C13(τ) and C23(τ) are acquired.In C12(τ),the γray peak coming from the inelastic reaction of 14-MeV neutrons with the casting is 5.0 ns before the neutron peak of fission chain.This time difference can estimate the casting position in container.The integrations of the C12(τ),C13(τ)and C23(τ) increase with the casting mass.The C23(τ) values of Pb component and DU casting are far less than the values of HEU casting.The C23(τ) integration of Pb component is 3.0% comparing with 15-kg HEU casting,while the integration of 4-kg HEU is 24.8%.The C23(τ) can demonstrate reliably the existence of HEU casting.The C12(τ) and C13(τ) values between HEU and DU casting with similar mass are different obviously.Conclusions:The spontaneous neutron decay constants of the components are stable,it can be used as an important parameter independently for the uranium casting verification.The correlation function C23(τ) is effective to judge the existence of uranium casting.By use of the integrations of the C12(τ),C13(τ) and C23(τ),the mass or enrichment of the uranium casting can be distinguished.关键词：Uranium casting;Accelerator;DT neutron;Correlation function;High speed data acquisition
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发布时间：2021-03-05 - 摘要：Background:Liquid lead-bismuth eutectic(LBE) is important spallation target materials and candidate coolant materials in accelerator driven subcritical(ADS)system.Purpose:Its thermodynamic physical properties are keys to understand the basic problems in ADS R&D.Methods:By the calculation of scientific laws as well as fitting other scholars’ experimental results,we tried to obtain the above thermodynamics physical properties.Results:By the calculation,we got formula about characteristic temperatures,density,specific heat,viscosity and thermal conductivity of liquid lead-bismuth alloy.And by fitting other scholars’ experimental results,we got the fitting formula.Conclusions:Finally,by the contrast analysis,we found that the fitting formula and calculation formula agree well,and fitting formula more approaches the experimental value with a high accuracy whose differential deviation is not over 1%.关键词：Accelerator driven subcritical(ADS);Liquid lead-bismuth eutectic(LBE);Thermophysical properties
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发布时间：2021-03-05 - 摘要：Background:The development of the nuclear industry caused uranium contamination to the environment.As an economical and environmental friendly technique to repair uranium contaminated soils,phytoremediation has attracted much attention in recent years,and the key to this technology is uranium bioavailability in soils.Purpose:The present work investigates the impact of several inorganic anions in soils on uranium desorption from the uranium contaminated soils.Methods:Leaching test and inductively coupled plasma-mass spectrometry(ICP-MS) was used in this study.Results:It was found that uranium desorption rate increased with CO32 concentration,and the equilibrium was obtained with resolution rate of 85% 90%.Uranium desorption rate could increase from 41% 53%when SO42 content was in the range of 5 40 g·L 1.While Cl had no effect on uranium desorption.Uranium desorption obtained equilibrium at a volume of 20 mL for strippant with 5-g uranium contaminated soil.In the former3 days,uranium desorption rate increased rapidly,and finally obtained equilibrium at 105-h with a desorption rate of90%.Conclusions:First,CO32 and SO42 have better effect on uranium desorption compared to other anions.Effect of CO32 was greater than SO42 due to a greater binding ability of CO32 to U(VI),while Cl had little effect.Second,the solvent volume and leaching time also impact uranium leaching yield.This study would be helpful to increase the knowledge of improving uranium bioavailability in the soil,which also laid a theoretical foundation to improve the efficiency of phytoremediation.关键词：Uranium;Desorption;Anions;Phytoremediation
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发布时间：2021-03-05 - 摘要：Background:Making an accurate diagnosis of bone metastasis earlier is very important for lung cancer clinical stage and making treatment plans.SPECT/CT fusion imaging provides more information than SPECT in diagnosing bone metastases from benign lesions of the solitary abnormal radioactive nuclide distribution in patients with lung cancer.Purpose:We want to investigate the value of SPECT/CT fusion imaging in identifying solitary bone metastases in patients with lung cancer.Methods:196 patients with lung cancer,whose bone scintigraphy demonstrated solitary abnormal radioactive nuclide distribution,were selected.SPECT/CT was employed for those lesions.SPECT and SPECT/CT bone images were analyzed by two seasoned nuclear medicine physicians separately.Each lesion was diagnosed with metastasis and benign lesion.The diagnosed results were compared with the final diagnosis.Results:196 patients with lung cancer had 196 lesions,112 bone metastatic lesions were proved to be bone metastatic criterion,89 metastatic lesions were found by SPECT,and 106 metastatic lesions were found by SPECT/CT.The sensitivity,specificity and accuracy of SPECT/CT and SPECT in the diagnosis of bone metastasis were 94.6%(106/112),92.9%(78/84),93.9%(184/196); 79.5%(89/112),78.6%(78/84) and 79.1%(155/196),respectively.The sensitivity,specificity and accuracy of SPECT/CT were higher than those of SPECT(χ2=11.25,P<0.05; χ2=7.00,P<0.05; χ2=18.35,P<0.05).Conclusions:SPECT/CT fusion imaging provided more information than SPECT imaging in distinguishing metastases from benign lesions of the solitary abnormal radioactive nuclide distribution in patients with lung cancer and improved the accuracy of the diagnosis of solitary bone metastasis of lung cancer.关键词：Lung neoplasms;Bone metastasis;Radionuclide imaging;SEPCT/CT;Diagnosis
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发布时间：2021-03-05 - 摘要：Background:Nuclear energy has the advantages of efficient,clean and reserves.Our country has launched a new type of nuclear reactor:thorium-based molten salt reactor nuclear system project since 2011.Purpose:We want to make sure the data of the nuclear reaction of n+Gd,including the total cross section,elastic scattering angular distribution,elastic scattering cross section,direct inelastic scattering cross section,absorption cross section,various of reaction channels cross section,double differential cross section of neutrons emitted,etc.The experimental data was compared and the theoretical results of nuclear reaction of n+Gd were given.Methods:First,the optical model is used to describe the nuclear reaction process,the reflection and refraction of light entering into a different media is used to describe the scattering and absorption of phenomenon of nuclear reaction,and a set of optical potential parameters is applied to describe the reaction.The total cross section,elastic scattering cross section,elastic scattering angular distributions and some other data were calculated based on the experimental data and this set of optical potential parameters.Then the direct inelastic scattering cross section was calculated on the basis of distorted wave Born approximation and optical potential parameters.Finally,based on the above calculation results and the theoretical of the unified Hauser-Feshbach and exciton model,the UNF program was used for calculating the variation of cross sections data and kinds of reaction channels.Results:The calculating results agree with the experimental data very well and can reflect the process of nuclear reaction approximately.Conclusions:The calculating results based on this set of optical potential parameters seem credible,and the process of nuclear reaction using the optical model assumption is reasonable.Based on the calculation of n+Gd,the Gd element can be used as a nuclear reactor control rod material,and nuclear reaction rate is controlled by absorbing neutrons,so that the nuclear reaction process goes more stable and more secure.关键词：Optical model potential;Unified Hauser-Feshbach theories;Total cross section;Elastic scattering angular distribution
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发布时间：2021-03-05 - 摘要：Background:Molten Salt Reactor(MSR) has several advantages over the other Generation IV reactor.Referred to the French CNRS research and compared to the fast reactor,super epithermal neutron spectrum reactor type is slightly lower and beading rate reaches 1.002.Purpose:The aim is to explore the best conversion zone layout scheme in the super epithermal neutron spectrum reactor.This study can make nuclear fuel as one way to solve the energy problems of mankind in future.Methods:Firstly,SCALE program is used for molten salt reactor graphite channel,molten salt core structure,control rods,graphite reflector and layer cladding structure.And the SMART modules are used to record the important actinides isotopes and their related reaction values of each reaction channel.Secondly,the thorium-uranium conversion rate is calculated.Finally,the better molten salt reactor core optimum layout scheme is studied comparing with various beading rates.Results:Breading zone layout scheme has an important influence on the breading rate of MSR.Central graphite channels in the core can get higher neutron flux irradiation.And more233Th can convert to233Pa,which then undergoes beta decay to become233U.The graphite in the breading zone gets much lower neutron flux irradiation,so the life span of this graphite can be much longer than that of others.Because neutron flux irradiation in the uranium molten salt graphite has nearly 10 times higher than the graphite in the breading zone,it has great impact on the thorium-uranium conversion rates.For the super epithermal neutron spectrum molten salt reactors,double salt design cannot get higher thorium-uranium conversion rates.The single molten salt can get the same thorium-uranium conversion rate,meanwhile it can greatly extend the life of graphite in the core.Conclusions:From the analysis of calculation results,Blanket breeding area in different locations in the core can change the breeding rates of thorium-uranium in the Blanket,but cannot improve the conversion rates of thorium-uranium in the uranium molten salts.For super thermal spectrum molten salt reactor,single molten salt graphite channel can provide CNRS design and almost can equivalent thorium-uranium conversion rate.At the same time,it can greatly reduce the levels of neutron flux in the moderator of graphite and improve the working economy of molten salt reactor.关键词：Molten salt reactor;Monte Carlo;Epithermal neutron energy spectrum;Breeding rate;Life of graphite
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发布时间：2021-03-05 - 摘要：Background:In the water-cooled passive heat removal system for molten salt reactor,the decay heat generated in molten salt can finally be transferred to the heat exchanger placed in water tank by natural circulation.Purpose:Based on the principles of high safety and simplification,there is a need to transfer the decay heat passively without using external power.Methods:The heat exchanger consists of a set of bundles submerged into the water tank with a tube header at each side.Based on the flow process,corresponding numerical model was constructed in the code of C++.Then the total heat exchange coefficient is got and the heat transfer area is calculated.Continually iterate the heat transfer area until the iteration stopping criterion is met,after that the dimensions of water tank are figured out.Results:While the decay power is 100 kW in the initial of the operation,the power of heat exchanger reaches the maximum value of 130 kW due to the low-temperature water in water tank.Then it drops quickly for the decrease of heat exchanger pressure and the rise of water temperature in water tank.When the heat exchanger pressure begins to rise,the heat exchanger power drops slower than before.The heat transfer ability begins to decrease quickly as the temperature difference between inside and outside of heat exchanger tubes lowers.Then it drops gradually as a result of the slowly changed pressure.During early operation,the heat exchanger pressure decreases because the steam generation rate is lower than the steam condensation rate.Then the condition varies as the heat exchanger power declines gradually.When boiling happens inside the water tank,the steam condensation rate raises due to the increasing heat transfer ability which makes the pressure of heat exchanger drops quickly.Afterwards,the heat exchanger pressure changes very slowly as the steam generation rate is approximate to the steam condensation rate.The mass of water in water tank remains unchanged essentially until the water begins to boil,then it starts to evaporate as the heat is transferred.The variation trend of the mass flow of condensate is similar to the heat exchange power of condenser.It decreases first and rises when the water reaches saturation.Then it lowers as the condenser pressure declines.Conclusions:The parameters of heat exchanger are calculated and the result shows that it can meet the requirements for heat exchange and has the self-regulation to some extent.The water tank can transfer the heat for a long time.Meanwhile the power can be adjusted by changing the water level in water tank.关键词：Molten salt reactor;Water-cooled passive heat removal system;Heat exchanger
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发布时间：2021-03-05 - 摘要：Background:Experimental Physics and Industrial Control System(EPICS) is the distributed control system software which is commonly used in large-scale experimental physics facilities.Purpose:We wish to apply it into the field of molten salt reactor relevant process control,e.g.HTS 1sttest loop of thorium-based molten salt reactor(TMSR),which is characterized by heating,circulation,cooling and other process control.Methods:During the development of EPICS based control system,the Simense S7-300 PLC and Yokogawa FA-M3 PLC hardware drivers specification format transformation has been done,to support the Autosave and devIocState plug,and ASYN serial communication between the DTI-1000 reference digital temperature indicator and the EPICS IOC has been developed with the StreamDevice packages,also EDM interface program was modified to support PV control of the "molten salt flow","fans","molten salt pump rotation",etc.by dynamic symbols.Results:EPICS based control system achieved the standardized communication of three hardwares with different types,the monitoring and storage of nearly 500 process variables,and the dynamic monitoring of control process.Conclusions:The EPICS-based control system can achieve the molten salt heating,feeding,cooling and other process control of the molten salt test loop.Safety analysis and research of control system requires further efforts to implement.关键词：HTS test loop;EPICS;PLC;Control system
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发布时间：2021-03-05
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