Figure 1.Cover of Issue 6, 2024
01
Synchrotron radiation technology and applications
Title: Optimal Design of Nanoradian-level Flexible Angular Displacement Adjustment Mechanism
Original link: https://www.hjs.sinap.ac.cn/thesisDetails#10.11889/j.0253-3219.2024.hjs.47.060101&lang=zh
Authors: Zhao Gaofeng, Zhu Wanqian, Zhang Limin, Liu Fangfang, Jin Limin, Xue Song
First Author Affilications: Shanghai Institute of Applied Physics, Chinese Academy of Sciences
DOI:10.11889/j.0253-3219.2024.hjs.47.060101
Key words: nanoradian level; flexible mechanism; Optimized design; genetic algorithms; Modal analysis
summary
In order to meet the needs of nanoradian angular displacement adjustment in synchrotron radiation, a set of redundant parallel flexible hinge rotation device was optimized and developed. The kinematic mechanism of the flexible mechanism was analyzed, and the overall static rotational stiffness of the mechanism was deduced by using the principle of virtual displacement, and its characteristics and the influence of hinge parameters on it were studied. According to the Lagrangian equation, the dynamic model is established, and the natural frequency of the mechanism in the direction of motion is derived. A mathematical optimization model was established, a static and dynamic dual-objective optimization design was carried out, and the genetic algorithm was used to optimize the objective function with nonlinear constraints. The finite element method is used to analyze the modality of the optimized mechanism, and the first four natural frequencies and mode shapes of the flexible mechanism are studied......
02
Accelerator technology, radiation technology and applications
Title: Optimal Voxel Analysis for Activity Reconstruction of Low- to Intermediate-level Radioactive Solid Waste
Original link: https://www.hjs.sinap.ac.cn/thesisDetails#10.11889/j.0253-3219.2024.hjs.47.060201&lang=zh
Authors: Jiang Xuezhi, Gu Weiguo, Shan Chenyu, Yang Hui, Wang Dezhong
First author affilications: Shanghai Jiao Tong University
DOI:10.11889/j.0253-3219.2024.hjs.47.060201
Key words: voxel division; number of conditions; pathological equations; Measurement time; Reconstruction accuracy
summary
In the process of reconstructing radionuclide activity of waste by traditional tomography γ scanning method (TGS), the measurement time is long due to the division of a large number of invalid voxels, and the reconstruction accuracy is low due to the iterative solution of the pathological equation. A voxel division optimization method is proposed, in which the circumferential division is based on the line source efficiency integration as the ring source efficiency, and the radial division is based on the irregular division to determine the optimal index weight. Through the random point source activity reconstruction experiment, the error of the voxel division optimization method and the traditional voxel division method was compared. For a 400 L cement waste bin with a radius of 35 cm, a coaxial HPGe detector with a detection efficiency of 40% was used at a distance of 74 cm from the center of the waste bin......
Topic: Development of Radioactive Sample Measurement Device for Small Angle Neutron Scattering Spectrometer
Original link: https://www.hjs.sinap.ac.cn/thesisDetails#10.11889/j.0253-3219.2024.hjs.47.060202&lang=zh
Authors: Hu Wenyao, Yan Shibo, Li Tianfu, Wang Zijun, Chen Zhong, Liu Rongdeng, Wang Chenglong, He Xinfu, Ran Huaichang, Sun Kai, Chen Dongfeng
First author's affiliation: China Institute of Atomic Energy
DOI:10.11889/j.0253-3219.2024.hjs.47.060202
Key words: small-angle neutron scattering; radioactive specimens; nanostructures; A508-III steel
summary
The study of irradiated specimens is of great significance for evaluating the properties of materials. Due to its radioactivity, conventional characterization methods are limited, while Small-Angle Neutron Scattering (SANS) technology is almost unaffected by γ and β rays, and sample preparation is simple. Relying on the small-angle neutron scattering spectrometer of the China Advanced Research Reactor, a radioactive sample measurement device was developed for the measurement and analysis of the internal nanostructure of the radioactive sample. The shield thickness of the device was optimized using Monte Carlo simulations, combined with automatic sample change and remote control, to improve experimental efficiency and safety. The small-angle neutron scattering experiment of the A508-III steel irradiation supervised sample was successfully carried out by using this device, and the results showed that the low-dose long-period irradiation had little effect on the nanostructure of the pressure vessel steel. This device and related technical methods can be used for the nanostructure characterization of radioactive specimens.
03
Nuclear Chemistry, Radiochemistry, Radiopharmaceuticals and Nuclear Medicine
题目：FLiBe熔盐中铀与镧系（Eu、Sm、Yb、La、Ce和Ho）氟化物的电化学性质及分离
Original link: https://www.hjs.sinap.ac.cn/thesisDetails#10.11889/j.0253-3219.2024.hjs.47.060301&lang=zh
Authors: Jiang Feng, Huang Wei, She Changfeng, Fu Haiying, Gong Yu
First Author Affilications: Shanghai Institute of Applied Physics, Chinese Academy of Sciences
DOI:10.11889/j.0253-3219.2024.hjs.47.060301
Key words: FLiBe molten salt; Uranium; Lanthanide; electrochemical behavior; Electrolytic separation
summary
The electrochemical method of post-processing separation of spent fuel in molten salt medium is one of the most widely studied technologies in dry post-processing, and its core content is to realize the separation of actinides and lanthanides by electrolysis. In this paper, cyclic voltammetry, square wave voltammetry and potentiostatic electrolysis were used to study the electrochemical behavior and separation feasibility of UF₄ and LnF₃ (Ln=Eu, Sm, Yb, La, Ce and Ho) in FLiBe(LiF-BeF2) molten salts, and the electrolytic separation of UF₄ and LnF₃ was carried out in the FLiBe-UF₄-LnF₃ mixed molten salt system using W electrode. The results show that the redox reaction of U⁴⁺ on an inert tungsten (W) electrode is divided into two steps......
Title: Experimental study on microbial mineralization to remove contaminants from ground-leaching uranium groundwater
Original link: https://www.hjs.sinap.ac.cn/thesisDetails#10.11889/j.0253-3219.2024.hjs.47.060302&lang=zh
Authors: He Guicheng, Zhu Xiaoyu, Li Yongmei
First Author's Affiliation: University of South China
DOI:10.11889/j.0253-3219.2024.hjs.47.060302
Key words: microbial mineralization; ground-leaching uranium mining; Groundwater; Uranium; contaminant
summary
Microbial-induced Calcium Carbonate Precipitation (MICP) technology can mineralize and remove pollutants from groundwater. In this paper, Bacillus pasteurii was selected to analyze its acid resistance and uranium tolerance, and the effects of initial U(VI) concentration, Ca²⁺ concentration, pH value, bacterial concentration and mineralization time on the removal of contaminants by MICP were explored, and the mechanism of MICP mineralization and decontamination was revealed. The results showed that Bacillus pasteurii had good urease activity at pH 4 and could adapt to groundwater with a concentration of 100 mg∙L⁻¹ U(VI). When the initial pH was 4, the uranium concentration was 50 mg∙L⁻¹, the Ca²⁺ concentration was 8 000 mg∙L⁻¹, and the MICP mineralization time was 48 h......
Title: Study on γ radiation decomposition and extraction properties of TODGA in kerosene media
Original link: https://www.hjs.sinap.ac.cn/thesisDetails#10.11889/j.0253-3219.2024.hjs.47.060303&lang=zh
Authors: Nong Shuying, Zheng Jiawei, Yang Shuyi, Yang Anbo, Wu Yan
First Author's Affiliation: CNNC 404 Co., Ltd
DOI:10.11889/j.0253-3219.2024.hjs.47.060303
Key words: TODGA; ultra-performance liquid chromatography; γ irradiation; radiation decomposition; extraction
summary
N,N,N',N'-tetraoctyl-diglycolamide (TODGA) is an amide pod ether extractant for the extraction and separation of actinides with wide development prospects. In order to study the γ irradiation performance of TODGA in kerosene medium, the effect of γ absorbed dose on the radiation of TODGA under different nitric acid concentrations in the aqueous phase was studied by using ultra-high performance liquid chromatography (HPLC) and kerosene as diluent. The extraction performance of TODGA-kerosene-3 mol∙L-1 nitric acid mixture system on alkaline earth metals and lanthanides after irradiation was evaluated. The results show that the radiolysis rate of TODGA decreases gradually with the increase of nitric acid concentration in the system, and when 4 mol∙L-1 nitric acid aqueous solution is added to the aqueous phase, the radiolysis can be inhibited by 18% compared with the aqueous solution without nitric acid......
04
Nuclear Electronics & Instrumentation
Title: Research on Gaussian Forming Algorithm for Nuclear Signals Based on Trigonometric Functions
Original link: https://www.hjs.sinap.ac.cn/thesisDetails#10.11889/j.0253-3219.2024.hjs.47.060401&lang=zh
Authors: Qian Yunchen, Zhou Jianbin, Liu Quanwei, Ma Yingjie, Liu Yi, Hong Xu
First Author's Affiliation: Chengdu University of Technology
DOI: 10.11889/j.0253-3219.2024.hjs.47.060401
Key words: digital nuclear pulse signal; Gaussian-like forming; Trigonometric numerical forming; Energy resolution
summary
Gaussian signals have the advantages of high signal-to-noise ratio, resistance to ballistic deficits, and easy extraction amplitude. Therefore, in nuclear radiation measurement systems, the Gaussian shaping of nuclear signals is widely used in the filtering and amplitude extraction of detector output signals. However, the real-time Gaussian nucleus pulsed signal is still challenging. The Gaussian-like signals output by the common Sallen-Key filter and CR-(RC)m filter also have problems such as poor symmetry and undershoot. In this paper, we propose a Gaussian-like pulse shaping algorithm for biexponential signals based on trigonometric functions. Based on the trigonometric function, the algorithm can obtain a left-right symmetrical Gaussian-like signal (1-cosx) through translation and inversion, and the digital recursion of the algorithm is derived by the Z-transform method. The simulation and measured results show that......
Title: Position-sensitive ³He proportional counting tube position-resolution performance based on time difference method
Original link: https://www.hjs.sinap.ac.cn/thesisDetails#10.11889/j.0253-3219.2024.hjs.47.060402&lang=zh
Authors: Wang Xinyue, Liu Guorong, Li Jinghuai, Liang Qinglei, Zhou Hao, Tian Yuan
First author's affiliation: China Institute of Atomic Energy
DOI:10.11889/j.0253-3219.2024.hjs.47.060402
Key words: position-sensitive; 3He proportional counting tube; neutron positioning; Monte Carlo simulation; time difference method; Location resolution
summary
Neutron positioning technology can be used to monitor spent fuel reprocessing processes to avoid nuclear criticality safety incidents. The Monte Carlo (MC) algorithm was used to simulate the effects of different neutron emission modes, ³He air pressure, pipe diameter, and moderator thickness on the position-sensitive 3He proportional counting tube's position resolution and detection efficiency. For the position-sensitive ³He proportional counting tube with a diameter of 2.54 cm, a sensitive zone length of 80 cm, and a ³He air pressure of 405 300 Pa, the MC simulation results show that the position resolution ability of each axial direction is the same, and the position resolution limit for the thermal neutron point source is 0.17 cm. When the moderator body thickness is 5 cm and the 244Cm source is close to the outer wall of the moderator, the neutron detection efficiency is 3.0%, and the position resolution is 9.25 cm......
05
Nuclear physics, interdisciplinary research
Title: Establishment and Application of Zirconium Alloy Irradiation Deformation Data Mining Library Based on Mesoscopic Model
Original link: https://www.hjs.sinap.ac.cn/thesisDetails#10.11889/j.0253-3219.2024.hjs.47.060501&lang=zh
Authors: Jun Huang, Zikang Zhang, Guisen Liu, Yao Shen
First author affilications: Shanghai Jiao Tong University
DOI:10.11889/j.0253-3219.2024.hjs.47.060501
Key words: zirconium alloy; irradiation deformation; mesoscopic model; data mining library; Viscoplastic self-consistent model
summary
In the field of nuclear industry, zirconium alloy, as a structural material, is subjected to the comprehensive effects of heat, force and neutron irradiation during the irradiation process, and irradiation deformation occurs, which affects its reliability. The study and prediction of irradiation deformation of zirconium alloys plays a key role in ensuring the safe and economical operation of the reactor. In this study, we collected the experimental data of irradiation deformation of zirconium alloys in the published literature, and established a database containing the experimental data and their detailed descriptions. On this basis, the database was used to explore the rules, and the self-developed mesoscopic model was combined with the model verification and data mining. In particular, more than 50 sets of preliminary data in the database were mined, and the correlation between model parameters and control variables was discussed. Discover ...... through data mining
Title: Effect of ZnO on the Mo leaching rate of simulated high-level radioactive waste liquid in borosilicate vitrified solidified liquid and its model prediction
Original link: https://www.hjs.sinap.ac.cn/thesisDetails#10.11889/j.0253-3219.2024.hjs.47.060502&lang=zh
Authors: Dong Hailong, Dai Chen, Li Zhongdi, Chen Shubin, Fan Sijun, Zhang Liyan
First Author's Affiliation: China Nuclear Power Engineering Co., Ltd
DOI:10.11889/j.0253-3219.2024.hjs.47.060502
Key words: borosilicate vitrified solids; Simulating high-level radioactive waste; leaching rate; Genetic mimetic of glass structure
summary
For high-molybdenum nuclear waste vitrified bodies, the Mo leaching rate is one of the key product properties. In the study of the formulation of borosilicate cured glass with a high MoO₃ (mass fraction of about 3%) simulated high-level radioactive waste liquid, a series of changes of ZnO content were designed, the Mo leaching rate was tested, and a mathematical statistical structure prediction model of Mo leaching rate was established and verified based on the experimental data. The results showed that the leaching of Mo was mainly affected by the oscillating vibration of Si-O-Si at about 530 cm⁻¹ and the bending vibration of Si-O-Si in the Q4 group at about 1 180 cm⁻¹, and the relative concentrations of B₂O₃, ZrO₂ and alkali metals would affect the leaching of Mo. In this complex glass system......
Title: Effect of heat treatment on the microstructure and mechanical properties of laser cladding GX4CrNi13-4
Original link: https://www.hjs.sinap.ac.cn/thesisDetails#10.11889/j.0253-3219.2024.hjs.47.060503&lang=zh
Authors: He Linghuan, Li Jiamin, Zhang Huawei, Hou Juan, Tian Xinni, Huang Aijun
First Author Affilications: University of Shanghai for Science and Technology
DOI:10.11889/j.0253-3219.2024.hjs.47.060503
Key words: martensitic stainless steel; laser cladding; inverter austenite; heat treatment toughening; coefficient of thermal expansion; Austenite transition temperature
summary
Laser cladding has been focused on in the field of laser remanufacturing due to its low cost and high efficiency, and GX4CrNi13-4 martensitic stainless steel manufactured by laser cladding is a widely used structural material in nuclear power plants. In order to improve the problem of low plasticity of laser cladding parts, it is necessary to adjust the microstructure of heat treatment to improve its mechanical properties. GX4CrNi13-4 stainless steel samples were prepared by laser cladding technology, and the heat treatment organization was controlled by the organization. Firstly, the austenitic phase transformation starting temperature of the alloy is 620 °C, which is used as the reference temperature for the development of heat treatment process. Two heat treatment processes, solution aging (1 050 °C for 1 h + 550 °C for 4 h, solution aging treatment) and single aging (620 °C for 2 h, single aging treatment), were developed, and the ...... were compared and studied
06
Nuclear Energy Science and Engineering
Title: Effect of core structure changes on nuclear reactivity of molten salt reactor bulk graphite components
Original link: https://www.hjs.sinap.ac.cn/thesisDetails#10.11889/j.0253-3219.2024.hjs.47.060601&lang=zh
Authors: Cao Jintong, Zhu Guifeng, Gu Zhiyu
First Author Affilications: Shanghai Institute of Applied Physics, Chinese Academy of Sciences
DOI:10.11889/j.0253-3219.2024.hjs.47.060601
Key words: molten salt pile; graphite components; core structure; reactivity; Monte Carlo simulation
summary
Due to the fluidity of the molten salt reactor fuel, the change of core structure will lead to changes in the distribution of core fuel and the loading capacity, which will affect the physical characteristics of the core. In this paper, based on the core design model of a new solid hexagonal graphite module molten salt reactor, the MCNP program is used to analyze the small geometric changes such as deformation and displacement of the core components caused by thermal expansion, fluid erosion, reactor body vibration and graphite irradiation deformation, and the influence of these core structure changes on the reactivity is studied. The results show that the change of core structure caused by thermal expansion introduces negative reactivity. The reactivity introduced by the shift of the graphite module caused by fluid erosion and the vibration of the reactor body is fluctuating, but the overall trend is that the graphite module shifts to the center of the reactor, introducing positive reactivity, and shifting to the outer part of the reactor and introducing negative reactivity. In order to ensure the safe operation of the reactor, the graphite components need to be confined to a certain range......
Title: Influence of reflected neutrons on the characteristic parameters of metal fast neutron pulse reactors
Original link: https://www.hjs.sinap.ac.cn/thesisDetails#10.11889/j.0253-3219.2024.hjs.47.060602&lang=zh
Authors: Guo Shuwei, Chen Zhenping, Jiang Xinbiao, Li Da, Zhang Keying, Zhang Xinyi, Wang Lipeng, Xie Jinsen, Yu Tao
First Author's Affiliation: University of South China
DOI:10.11889/j.0253-3219.2024.hjs.47.060602
Key words: fast neutron pulse reactor; reflected neutrons; nuclear thermal coupling; point pile dynamics; Security analytics
summary
Fast neutron pulse reactors are sensitive to wall-reflected neutrons, which will change the waveform of fast neutron pulse reactors, which may adversely affect the operation safety of pulse reactors when there are more reflected neutrons. In this paper, a "nuclear-thermal-mechanical" coupling method is established by coupling the point reactor dynamics method considering the neutron effect of wall reflection, the Monte Carlo neutron calculation method and the ANSYS thermodynamic calculation method, and the transient process of Godiva-I fast neutron pulse reactor with the neutron effect reflected by the wall is analyzed. The results show that the reflected neutrons increase the trailing edge of the pulse, make the reactivity of the flushing floor lower, and increase the displacement and stress of the core.
Title: Motion Characteristics and Drag Coefficient Model of Air Bubbles in Liquid Lead-Bismuth Metal
Original link: https://www.hjs.sinap.ac.cn/thesisDetails#10.11889/j.0253-3219.2024.hjs.47.060603&lang=zh
Authors: Luo Haotian, Liu Li, Yuan Junjie, Bao Ruiqi, Tian Xiaoyan, Li Da, Gu Hanyang
First author affilications: Shanghai Jiao Tong University
DOI:10.11889/j.0253-3219.2024.hjs.47.060603
Key words: lead-bismuth fast reactor; SGTR accidents; bubble-liquid metal two-phase flow; bubble dynamics; Drag coefficient
summary
When the Steam Generator Tube Rupture (SGTR) accident occurred in the lead-bismuth fast reactor, the high-temperature liquid lead-bismuth alloy (LBE) in the primary circuit interacted with the high-pressure supercooled water in the secondary circuit to produce a large amount of steam, and these bubbles may enter the core under the carrying action of LBE, causing local heat transfer deterioration and power transients, which seriously affect the safe operation of the reactor. Understanding the motion characteristics and dynamic behavior of air bubbles in liquid LBE, and developing a drag coefficient model suitable for bubble migration in LBE are the basis for the safety assessment of SGTR accident cores. Based on the CLSVOF (Coupled Level-Set and Volume-Of-Fluid) method, a three-dimensional numerical model of the migration motion of air bubbles in high-temperature liquid LBE was established......
Title: Levitation Control and Simulation of CAT-1 Dipole Field Superconducting Magnets
Original link: https://www.hjs.sinap.ac.cn/thesisDetails#10.11889/j.0253-3219.2024.hjs.47.060604&lang=zh
Authors: Wang Yalin, Liu Yunhui, Zhang Guoshu, Du Junjie, Yang Shuran, Gong Yudong
First Author's Affiliation: East China University of Technology
DOI:10.11889/j.0253-3219.2024.hjs.47.060604
Key words: CAT-1; dipole field magnetic confinement; Magnetic levitation; superconducting rings; Levitation control
summary
China Astro-Torus 1 (CAT-1) is a suspended dipole field magnetic confinement device, mainly used for experimental research on dipole field plasma physics, requiring a central suspended superconducting magnet to be stably suspended for at least 5 h without cooling and power. In order to ensure the stable suspension of the 1 200 kg and 5 MA central levitation magnet rings, the Simulink model of the control system was established and simulated, and the influence of PID (Proportion-Integral-Derivative) control strategy on stability control was studied based on the Routh-Hurwitz stability criterion, and the range of stability control parameters was determined......
Title: Research on Efficient Global Sensitivity Analysis Methods for Passive Systems under Marine Conditions
Original link: https://www.hjs.sinap.ac.cn/thesisDetails#10.11889/j.0253-3219.2024.hjs.47.060605&lang=zh
Authors: Zhang Shiqi, Peng Minjun, Xia Genglei, Wang Chenyang, Shang He
First author's affiliation: Harbin Engineering University
DOI:10.11889/j.0253-3219.2024.hjs.47.060605
Key words: passive safety system; sensitivity analysis; low-rank approximation; Sobol; Marine conditions
summary
The passive system contains a large number of uncertainty parameters in the operation process, and its reliability is generally evaluated by best estimation and uncertainty analysis, and an important step in the evaluation process is the sensitivity analysis of the parameters, which is used to identify the key parameters of the system to reduce the complexity of the model. In order to improve the efficiency of traditional global sensitivity analysis in complex nuclear power systems due to its high computational cost, this study proposes to use the Low-Rank Approximations (LRA) method to improve the Monte Carlo-based Sobol method, and uses multiple benchmark questions to verify the effectiveness of the proposed method. Finally, this method was used to analyze the sensitivity of the passive waste heat discharge system of an integrated pressurized water reactor. The results showed ......
Title: Study on the Effect of Plate Fuel Enrichment on Fuel Performance
Original link: https://www.hjs.sinap.ac.cn/thesisDetails#10.11889/j.0253-3219.2024.hjs.47.060606&lang=zh
Authors: Yue Zhiying, He Yanan, Liu Hongquan, Wu Yingwei, Zhang Jing, Su Guanghui, Tian Wenxi, Qiu Suizheng
First Author Affilications: Xi'an Jiaotong University
DOI: 10.11889/j.0253-3219.2024.hjs.47.060606
Keywords: neutron physics; thermal hydraulics; fuel performance; U₃Si₂-Al fuel; Multiphysics coupling
summary
The enrichment of nuclear fuel has an important impact on fuel performance. In order to explore the effect of fuel enrichment on the performance of U₃Si₂-Al plate fuels, based on the BEEs-Plates/OpenMC/ZEBRA coupling program, the neutron physics-thermal-hydraulic-fuel performance coupling calculations were carried out for modules with 15%, 20% and 25% enrichment, and the neutron physical parameters and fuel performance parameters were analyzed when the average fuel consumption of the modules reached 125.71 GWd∙tU⁻¹. The calculation results show that the higher the enrichment of the fuel assembly, the greater the volumetric strain, creep strain and plastic strain. The analysis of neutron physical parameters shows that the power density of modules with 25% enrichment is about 18% higher than that of modules with 15% enrichment, and the maximum fuel consumption of modules with higher enrichment is also larger. The results of the analysis of fuel performance parameters show that the plastic strain of the module with 25% enrichment is about 40% higher than that of the module with 15% enrichment, indicating that the module with higher enrichment is more likely to fail.
Title: Preparation process and properties of graphene oxide doped UO₂ cores
Original link: https://www.hjs.sinap.ac.cn/thesisDetails#10.11889/j.0253-3219.2024.hjs.47.060607&lang=zh
Authors: Feng Wen, Jiangping Du, Yumeng Zhao, Ning Yang, Zongyi Shao, Wei Liu, Zhenfang Cai
First Author's Affiliation: Key Laboratory of Preparation Technology of Irradiation Special Components for China Nuclear Reactor
DOI:10.11889/j.0253-3219.2024.hjs.47.060607
Key words: graphene oxide doping modification; UO₂ cores; solid-liquid mixing method; Discharge plasma sintering; Thermal conductivity
summary
Graphene oxide (GO) doped modified uranium dioxide (UO₂) pellets are one of the key directions in the research of high-performance nuclear fuels. In order to achieve the uniform distribution and effective control of the doping amount of GO in the UO₂ core, UO₂ powders with different doping amounts of GO were prepared by solid-liquid mixing method and ammonium diuranate (ADU) co-precipitation method, and the effects of the milling method and the doping amount of GO on the mixing uniformity of GO in UO₂ were studied. UO₂-GO pellets with different GO doping amounts were prepared by spark plasma sintering, the influence of different sintering parameters was explored, and the performance of the fuel pellets was tested. The results showed ......