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Development of a subchannel code for blockage accidents of LMFRs based on the 3D fuel rod model

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nuclear science and Techniques 2022年第3期33卷 30-44页

作者： Xiao Luo Lian-Kai Cao Wen-Pei Feng Hong-Li Chen School of Nuclear Science and Technology University of Science and Technology of ChinaHefei 230026China

To predict the thermal-hydraulic(T/H)parameters of the reactor core for liquid-metal-cooled fast reactors(LMFRs),especially under flow blockage accidents,we developed a subchannel code called KMC-FB.This code uses a time-dependent,four-equation,singlephase flow model together with a 3D heat conduction model for the fuel rods,which is solved by numerical methods based on the finite difference method with a staggered mesh.Owing to the local effect of the blockage on the flow field,low axial flow,increased forced crossflow,and backflow occur.To more accurately simulate this problem,we implemented a robust and novel solution method.We verified the code with a low-flow(~0.01 m/s)and large-scale blockage case.For the preliminary validation,we compared our results with the experimental data of the NACIE-UP BFPS blockage test and the KIT19ROD blockage test.The results revealed that KMC-FB has sufficient solution accuracy and can be used in future flow blockage analyses for LMFRs.

关键词： Subchannel method Code development Blockage accident Liquid-metal-cooled fast reactor

Development and validation of a new oxide fuel rod performance analysis code for the liquid metal fast reactor

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nuclear science and Techniques 2022年第5期33卷 167-177页

作者： Guang-Liang Yang Hai-Long Liao Tao Ding Hong-Li Chen School of Nuclear Science and Technology University of Science and Technology of ChinaHefei230026China

The integrity and reliability of fuel rods under both normal and accidental operating conditions are of great importance for nuclear reactors.In this study,considering various irradiation behaviors,a fuel rod performance analysis code,named KMC-Fueltra,was developed to evaluate the thermal–mechanical performance of oxide fuel rods under both normal and transient conditions in the LMFR.The accuracy and reliability of the KMC-Fueltra were validated by analytical solutions,as well as the results obtained from codes and experiments.The results indicated that KMC-Fueltra can predict the performance of oxide fuel rods under both normal and transient conditions in the LMFR.

关键词： Fuel rod analysis code Thermal-mechanical performance Irradiation behaviors Pellet-cladding mechanical interaction Liquid metal fast reactor

Procedure for determining the number of thermal diffusion columns in square cascade for separation of Ne stable isotopes

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nuclear science and Techniques 2023年第5期34卷 47-55页

作者： Fatemeh Mansourzadeh Mohammad Mahdi Shadman Javad Karimi Sabet Valiyollah Ghazanfari nuclear Fuel Cycle Research school Nuclear Science and Technology Research InstituteTehranIran

The thermal diffusion column represents one method of separating stable isotopes.This method is advantageous for smallscale operations because of the simplicity of the apparatus and small inventory,especially in gas-phase operations.Consequently,it has attracted attention for its applicability in tritium and noble gas separation systems.In this study,the R cascade was used to design and determine the number of columns.A square cascade was adopted for the final design because of its flexibility,and calculations were performed to separate 20Ne and 22Ne isotopes.All the R cascades that enriched the Ne isotopes by more than 99%were investigated,the number of columns was determined,and the square cascade parameters were optimized using the specified columns.Additionally,a calculation code“RSQ_CASCADE”was developed.A unit separation factor of three was considered,and the number of studied stages ranged from 10 to 20.The results showed that the column separation power,relative total flow rate,and required number of columns were linearly related to the number of stages.The separation power and relative total flow decreased and the number of columns increased as the stage number increased.Therefore,a cascade of 85 columns is recommended to separate the stable Ne isotopes.These calculations yielded a 17-stage square cascade with five columns in each stage.By changing the stage cut,feed point,and cascade feed flow rate,the best parameters for the square cascade were determined according to the cascade and column separation powers.As the column separation power had a maximum value in cascade feed 50,it was selected for separating Ne isotopes.

关键词： Stable isotope Thermal diffusion Cascade Separation Neon

An effective process for the separation of U(Ⅵ),Th(Ⅳ)from rare earth elements by using ionic liquid Cyphos IL 104

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Chinese Chemical Letters 2022年第7期33卷 3422-3428页

作者： Jiawei Lu Kebao He Yi Wang Geng Chen Hanqin Weng Mingzhang Lin School of Nuclear Science and Technology University of Science and Technology of ChinaHefei 230027China

Separation and recovery of U(Ⅵ)and Th(Ⅳ)from rare earth minerals is a very challenging work in rare earth industrial production.In the present study,a homemade membrane emulsification circulation(MEC)extractor was used to separate U(Ⅵ)and Th(Ⅳ)from rare earth elements by using Cyphos IL 104 as an extractant.Batch experiments were carried out using a constant temperature oscillator to investigate the extraction parameters of the single element and the results indicated that Cyphos IL 104could reach the extraction equilibrium within 30 min for all the three elements,i.e.,U(Ⅵ),Th(Ⅳ),and Eu(Ⅲ).Besides,the MEC extractor possessed a strong phase separation ability.The extraction efficiencies of U(Ⅵ),Th(Ⅳ),La(Ⅲ),Eu(Ⅲ)and Yb(Ⅲ)increased with the increase of pH.La(Ⅲ),Eu(Ⅲ)and Yb(Ⅲ)were hardly extracted when pH≤1.50,which was beneficial for effectively separating U(Ⅵ)and Th(Ⅳ)from La(Ⅲ),Eu(Ⅲ)and Yb(Ⅲ).In the multi-stages stripping experiments,when the stripping stage number was 3,the effective separation could be achieved by using HCl and H_(2)SO_(4),since the stripping efficiency reached 80.0%and 100.0%for Th(Ⅳ)and U(Ⅵ),respectively.Slope method and FT-IR spectra showed that Cyphos IL 104 reacted with U(Ⅵ)and Th(Ⅳ)by chelation mechanism.The extraction of multi-elements indicated that U(Ⅵ)and Th(Ⅳ)could be well separated from the solution which contains all rare earth elements,and the extraction efficiencies of U(Ⅵ)and Th(Ⅳ)both were close to 100.0%.Based on the above experimental results,a flowchart for efficient separation of U(Ⅵ)and Th(Ⅳ)from rare earth elements was proposed.

关键词： Rare earth elements Actinides Solvent extraction Membrane emulsification Ionic liquid

Neural network study of the nuclear ground-state spin distribution within a random interaction ensemble

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nuclear science and Techniques 2024年第3期35卷 216-227页

作者： Deng Liu Alam Noor A Zhen-Zhen Qin Yang Lei school of Mathematics and Physics Southwest University of Science and TechnologyMianyang 621010China School of Nuclear Science and Technology Southwest University of Science and TechnologyMianyang 621010China

The distribution of the nuclear ground-state spin in a two-body random ensemble(TBRE)was studied using a general classification neural network(NN)model with two-body interaction matrix elements as input features and the corresponding ground-state spins as labels or output predictions.The quantum many-body system problem exceeds the capability of our optimized NNs in terms of accurately predicting the ground-state spin of each sample within the TBRE.However,our NN model effectively captured the statistical properties of the ground-state spin because it learned the empirical regularity of the ground-state spin distribution in TBRE,as discovered by physicists.

关键词： Neural network Two-body random ensemble Spin distribution of nuclear ground state

Examination of machine learning for assessing physical effects:Learning the relativistic continuum mass table with kernel ridge regression

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Chinese Physics C 2023年第7期47卷 138-150页

作者：杜晓凯郭鹏吴鑫辉张双全 State Key Laboratory of nuclear Physics and technology School of PhysicsPeking UniversityBeijing 100871China

The kernel ridge regression(KRR)method and its extension with odd-even effects(KRRoe)are used to learn the nuclear mass table obtained by the relativistic continuum Hartree-Bogoliubov theory.With respect to the binding energies of 9035 nuclei,the KRR method achieves a root-mean-square deviation of 0.96 MeV,and the KRRoe method remarkably reduces the deviation to 0.17 MeV.By investigating the shell effects,one-nucleon and twonucleon separation energies,odd-even mass differences,and empirical proton-neutron interactions extracted from the learned binding energies,the ability of the machine learning tool to grasp the known physics is discussed.It is found that the shell effects,evolutions of nucleon separation energies,and empirical proton-neutron interactions are well reproduced by both the KRR and KRRoe methods,although the odd-even mass differences can only be reproduced by the KRRoe method.

关键词： machine learning kernel ridge regression relativistic continuum Hartree-Bogoliubov theory nuclear mass table

Determination of the half-life of^(184g)Re and the isomeric ratio of^(184m,g)Re induced by D-T neutrons

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Chinese Physics C 2022年第11期46卷 168-176页

作者：兰长林魏玉婷王家豪杨宪林姜功葛裕杰徐超冯蠡李小军 School of Nuclear Science and Technology Lanzhou UniversityLanzhou 730000China

The isomeric ratio of^(184m,g)Re and the half-life of^(184g)Re were measured in the ^(185)Re(n,2n)^(184)Re reaction at 14.8 MeV,and the uncertainty was discussed in detail.The measurements were performed using the activation method implemented for a rhenium sample using the K-400 neutron generator at the Chinese Academy of Engineering Physics(CAEP).Isomeric state and ground state nuclei of ^(184)Re were identified by their γ-ray spectra.To eliminate the effect of the γ-ray emitted from the isomer on the counting of the ground state characteristic peaks,the isomeric ratio of^(184m,g)Re was calculated to be 0.29±0.11 according to the neutron activation cross-section formula.This result is consistent with previous data within the uncertainty and can be used to determine parameters that characterize the dependence of the level density on the excitation energy and angular momentum.Through exponential function fitting and a detailed discussion of the uncertainty evaluation,the half-life of^(184g)Re was determined as 35.43±0.16 d,which is consistent with the currently recommended value;however,the uncertainty assessment of the latter was barely documented.In addition,this study indicates that the half-life of the ground state can be obtained by eliminating the contamination of γ-rays emitted from the isomer,which provides the possibility of determining the half-lives of nuclides containing isomers.

关键词： Half-life ^(184)Re γ-ray spectrometry isomeric ratio

Development and application of a multi-physics and multi-scale coupling program for lead-cooled fast reactor

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nuclear science and Techniques 2022年第2期33卷 40-52页

作者： Xiao Luo Chi Wang Ze-Ren Zou Lian-Kai Cao Shuai Wang Zhao Chen Hong-Li Chen School of Nuclear Science and Technology University of Science and Technology of ChinaHefei 230026China China nuclear Power technology Research Institute Co.Ltd Shenzhen 518000China

In this study,a multi-physics and multi-scale coupling program,Fluent/KMC-sub/NDK,was developed based on the user-defined functions(UDF)of Fluent,in which the KMC-sub-code is a sub-channel thermal-hydraulic code and the NDK code is a neutron diffusion code.The coupling program framework adopts the"master-slave"mode,in which Fluent is the master program while NDK and KMC-sub are coupled internally and compiled into the dynamic link library(DLL)as slave codes.The domain decomposition method was adopted,in which the reactor core was simulated by NDK and KMC-sub,while the rest of the primary loop was simulated using Fluent.A simulation of the reactor shutdown process of M2LFR-1000 was carried out using the coupling program,and the code-to-code verification was performed with ATHLET,demonstrating a good agreement,with absolute deviation was smaller than 0.2%.The results show an obvious thermal stratification phenomenon during the shutdown process,which occurs 10 s after shutdown,and the change in thermal stratification phenomena is also captured by the coupling program.At the same time,the change in the neutron flux density distribution of the reactor was also obtained.

关键词： Multi-physics and multi-scale coupling method User-defined functions Dynamic link library Thermal stratification Lead-cooled fast reactor

Hybrid model for muon tomography and quantitative analysis of image quality

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nuclear science and Techniques 2022年第7期33卷 1-13页

作者： Si-Yuan Luo Yu-He Huang Xuan-Tao Ji Lie He Wan-Cheng Xiao Feng-Jiao Luo Song Feng Min Xiao Xiao-Dong Wang School of Nuclear Science and Technology University of South ChinaHengyang 421001China

Muon tomography is a novel method for the non-destructive imaging of materials based on muon rays,which are highly penetrating in natural background radiation.Currently,the most commonly used imaging methods include muon radiography and muon tomography.A previously studied method known as coinciding muon trajectory density tomography,which utilizes muonic secondary particles,is proposed to image low and medium atomic number(Z)materials.However,scattering tomography is mostly used to image high-Z materials,and coinciding muon trajectory density tomography exhibits a hollow phenomenon in the imaging results owing to the self-absorption effect.To address the shortcomings of the individual imaging methods,hybrid model tomography combining scattering tomography and coinciding muon trajectory density tomography is proposed and verified.In addition,the peak signal-to-noise ratio was introduced to quantitatively analyze the image quality.Different imaging models were simulated using the Geant4 toolkit to confirm the advantages of this innovative method.The simulation results showed that hybrid model tomography can image centimeter-scale materials with low,medium,and high Z simultaneously.For high-Z materials with similar atomic numbers,this method can clearly distinguish those with apparent differences in density.According to the peak signal-to-noise ratio of the analysis,the reconstructed image quality of the new method was significantly higher than that of the individual imaging methods.This study provides a reliable approach to the compatibility of scattering tomography and coinciding muon trajectory density tomography.

关键词： Monte Carlo simulation Muon tomography Image reconstruction