最新刊期
卷 0 ， 期 0 ， 2020
- 摘要：Background: In order to improve the synchrotron performance in the constant current mode, attentions should be paid to problems such as non-linear beam dynamics, broadband beam impedance, and position disturbance, etc. Purpose: To address these problems, a bunch by bunch data acquisition system(BBDAQ) is implemented for real-time bunch position monitoring, as well as the off-line data analysis for the Shanghai Synchrotron Radiation Facility(SSRF) storage ring. It can be applied to optimize new equipment impedance, filling pattern, injection mode, and raise threshold value of current instability. Methods: This BBDAQ developed at SSRF consists a RF front end to filter and expand bunch signal to 2 ns, a data acquisition and processing card to sample bunch signal with four 125-MHz ADCs, which make an equivalent 500-MHz sampling rate, and the EPICS for post-processing to give bunch position and tune value. Results: Online experimental results show that the system can measure bunch by bunch position and tune value successfully. Conclusion: The development of bunch by bunch data acquisition system provides an efficient tool to analyze beam impedance, coupling instability, nonlinear dynamics. It makes further improvement of synchrotron performance visible.关键词：Bunch by bunch;Data acquisition;RF front end;Equivalent sampling;Bunch position
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发布时间：2021-03-05 - 摘要：Background: The α particle has a strong ionization but weak penetration ability, and some factors, such as α radioactive source self-absorption, incomplete charge collection, electronic noise and statistical fluctuation, etc. have significant influence on the experimental α spectra synthetically, which can lead to a long tail at low-energy side and serious spectra noise. Purpose: The aim is to reduce the statistical fluctuation and electronics noise in detector, so as to preprocess data for the deconvolution of α spectra. Methods: In this study a portable α spectrometer with a Au-Si surface barrier detector was applied to obtain α spectra of 239Pu under vacuum conditions of ?0.01 MPa, ?0.02 MPa, ?0.03 MPa, ?0.04 MPa and ?0.05 MPa. A discrete wavelet transform(DWT) method for α spectra smoothing and a new smoothing evaluation method were proposed, and tested on those spectra data for comparative study. Results: The results showed that DWT method had less damage on the peak compared with least squares polynomial smoothing method. The D(r) and ξ values of DWT were greater and χ2 values were closer to 1 compared with those of least squares polynomial smoothing method. Conclusion: The DWT method is better than the traditional least squares polynomial smoothing method in smoothing low-level and high noise α spectra.关键词：Low-level alpha spectra;Au-Si surface barrier detector;Discrete wavelet transform;Smoothing evaluation
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发布时间：2021-03-05 - 摘要：Background: Matrix effect of elements is always a hot and difficult problem in energy dispersive X-ray fluorescence(EDXRF). Purpose: A hybrid model based on fruit fly optimization algorithm(FOA) to optimize the least square vector machine(LSSVM) was put forward to calibrate the matrix effect between Ti and Fe in EDXRF. Methods: The X spectrum counting rate of Ti-Fe in five kinds of ore samples was measured using a CIT-3000SMEDXRF analyzer and electrical refrigeration semiconductor detector. In total 80 groups of data, there were 16 groups of data for each kind of ore samples. FOA was utilized to optimize the parameters of LSSVM, and the optimal model was used for predicting 30 groups of samples of Ti, Fe contents. Moreover, the default LSSVM of MATLAB and the hybrid model optimized by particle swarm optimization(PSO) and genetic algorithm(GA) were applied to predict the contents of Ti and Fe. And the results predicted by FOA-LSSVM were compared with those by PSO-LLSVM, GA-LSSVM and the default LSSVM. Results: There are 26 groups with the Ti, Fe contents predicted by FOA-LSSVM bearing a relative error of 1% compared with chemical analysis values, accounting for 86.67% of the total 30 groups; another 4 groups with the predicted values equal to chemical analysis values, accounting for 13.33%. The study showed that FOA-LSSVM possessed a high prediction precision. Conclusion: Comprehensive research indicates that it is feasible to calibrate the matrix effect between Ti and Fe by FOA-LSSVM model, and the FOA-LSSVM model is a preferred method.关键词：Fruit fly optimization algorithm(FOA);Matrix effect;Energy dispersive X-ray fluorescence analysis(EDXRF);Least square vector machine(LSSVM)
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发布时间：2021-03-05 - 摘要：Background: Creation of new germplasm derived from wheat can accelerate the genetic breeding of wheat. Purpose: Samples of the callus from immature embryo were irradiated by 60Co γ-ray to study their biological effects. Methods: The calluses were irradiated at the doses of 5 Gy, 10 Gy, 15 Gy, 20 Gy and 30 Gy(dose rate 10 Gy/min). And the physiological characters in M2 generation were observed. Results: The results showed that the rates of callus differentiation decreased with the increasing of doses. Morphological variations including leaf, stalk, plant type, panicle type and various physiological characters were observed in the M2 generation. Conclusion: The mutants were helpful for gene identification and gene functional analysis, and for breeding of new wheat variety as well.关键词：Wheat;Callus;60Co γ-ray;Mutagenic effects
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发布时间：2021-03-05 - 摘要：Background: With the development of nuclear technology, radionuclides are widely used in every walk of life, such as reactor, radiation breeding, radiopharmaceutical imaging diagnosis and therapy of disease, etc. While application of radioactive material becomes broader, the possibility of radioactive accident becomes higher. Purpose: In order to effectively treat and timely control the radioactive accident, effective protection therapies are indispensable. Fundamental measure that controls internal exposure is mainly accelerated by reducing absorption and elimination of radionuclides in the body, that is, to look for a suitable suction blocking agent or a radionuclide chelating agent. Methods: We modified fullerenes, and a new chelating agent(fullerene macrocyclic polyamine derivatives, CB) was synthesized via the introduction of Nitrogen-containing Heterocyclic functional perssad onto the surface of fullerene. Improved Karber method was applied, and LD50 of the compound was obtained. On the base of toxicity experiment, excretion promotion of CB to uranium was explored through the establishment of a mouse model of infection uranium. Results: The experimental results shown that the median lethal dose of CB was 1.767 mg, and CB could not change the bio-distribution of uranium significantly in mice. CB could reduce the accumulation of uranium in liver and bone in mice obviously, as compared with positive control group Diethylene triamine penlaacetic acid(DTPA) and blank control group. Conclusion: Our analyses suggest that CB possesses the potential chelating agent of U in mice.关键词：Uranium;Fullerene macrocyclic derivatives;Chelating agent
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发布时间：2021-03-05 - 摘要：Background: A 200 mm×200 mm two-dimensional positional sensitive detector(PSD) has been designd and constructed for the cold-neutron triple axis spectrometer(CTAS). The parameters of the PSD are necessary for evaluation and analysis of neutron scattering pattern obtained on CTAS and other instrument using PSD, mainly for the correction of angle and spectral shape due to the unequal solid angle and inhomogeneous efficiency of the flat PSD. Purpose: In order to obtain the working bias voltage, pixel size, spatial resolution, detection efficiency and its uniformity, a calibration method was proposed and tested for the PSD of CTAS. Methods: The calibration was carried out at the ATHOS three-axis spectrometer installed at the neutron guide No.1 of the 10-MW steady state reactor of the Budapest Neutron Centre. The focusing copper monochrometer provided well collimated(20’ divergence) neutron beam of wavelength equal to 0.572 nm with the second order equal to 0.286 nm. A black neutron detector having >99% efficiency at these wavelengths coated with boron shielding was used for efficiency test and a 0.5-mm wide Cd slit was used for the determination of pixel size and spatial resolution of the PSD. Results: The experimental results show that the working bias voltage is 4.2-4.4 kV, pixel size 0.32 mm(H&V), the detector spatial resolution of 2.15 mm(H)×2.04 mm(V), the detection efficiency of 90.47% and the efficiency uniformity better than 10%. Conclusion: The established method was successfully used in the PSD calibration, which can be extended to PSD R&D and data analysis of neutron spectrometer.关键词：Detector calibration;Position sensitive detector;Spatial resolution;Detection efficiency;Black detector
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发布时间：2021-03-05 - 摘要：Background: Based on general purpose CFD code Fluent, the PBMR-400 full load nominal condition thermal-hydraulics performance was studied by applying local thermal non-equilibrium porous media model. Purpose: In thermal hydraulics study of the gas cooled pebble bed reactor, the core of the reactor can be treated as macroscopic porous media with strong inner heat source, and the original Fluent code can not handle it properly. Methods: By introducing a UDS in the calculation domain of the reactor core and subjoining a new resistance term, we develop a non-equilibrium porous media model which can give an accurate description of the core of the pebble bed. The mesh of CFD code is finer than that of the traditional pebble bed reactor thermal hydraulics analysis code such as THERMIX and TINTE, thus more information about coolant velocity fields, temperature field and solid phase temperature field can be acquired. Results: The nominal condition calculation results of the CFD code are compared to those of the well-established thermal-hydraulic code THERMIX and TINTE, and show a good consistency. Conclusion: The extended local thermal non-equilibrium model can be used to analyse thermal-hydraulics of high temperature pebble bed type reactor.关键词：CFD(Computational Fluid Dynamics);Gas-cooled pebble bed reactor;Porous media
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发布时间：2021-03-05 - 摘要：Background: The Core Cooling and Monitoring System(CCMS) of CPR1000 nuclear power station supplies monitoring means for two primary state functions defined in State Oriented Procedure(SOP). Purpose: We aim to deal with the errors caused by L VSL measurement and discuss the influence on SOP accident treatment. Methods: The calculation formula of natural recirculation flow rate was estimated. The maximum flow rates of single phase natural recirculation(at the time of reactor trip) and two phase natural recirculation(the void fraction in hot leg was 0.2) were calculated. The impact on SOP due to the measurement error of L VSL was analyzed. Results: Firstly, in the condition of single phase recirculation, the estimated error of L VSL measurement induced by the natural recirculation was less than 1.6%. Secondly, in the condition of two phase natural recirculation, the natural recirculation induced an over-estimated error about 3.6% to L VSL measurement when the void fraction in hot leg was 0.2. Conclusion: As multi-parameters are adopted for SOP to diagnose the core cooling state, the implementation of the safety related operations is guaranteed.关键词：Natural circulation;Reactor vessel level;State orientation;Error
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发布时间：2021-03-05 - 摘要：Background: For the nuclear power plant, the flow resistance of steam generator primary nozzles is an important part of the primary flow resistance. Consequently, the study on the calculation method of the flow resistance and that on its main influence factor are of great significance to the design of the nuclear power plant. In engineering, the k-ε models, including Standard k-ε model, RNG k-ε model and Realizable k-ε model, are widely applied to the simulation of flow field. Purpose: We aim to make sure which of these k-ε models is the most appropriate to calculate the flow resistance of steam generator primary nozzles. And the influence of the chamfer on the flow resistance was studied. Methods: First of all, the k-ε models mentioned above were respectively used to simulate the flow field and calculate the flow resistance. The applicabilities of Standard k-ε model, RNG k-ε model and Realizable k-ε model were discussed via comparing the numerical results with those of the experiment. Then, the most appropriate model was adopted to study the influence of the chamfer on the flow resistance. Results: Compared with other k-ε models, Realizable k-ε model was the most appropriate one for the calculation of the flow resistance of steam generator primary nozzles. The chamfer was helpful for reducing the flow resistance, especially for the outlet nozzle. Conclusion: Numerical modeling can be used to determine an appropriate computing method for flow resistance of steam generator primary nozzles, and study the main influence factor on the flow resistance. This work may have certain reference value to the design of steam generators and the computation for flow resistance of other equipment in the nuclear power plant.关键词：Steam generator;Flow resistance;Numerical simulation
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发布时间：2021-03-05 - 摘要：Background: Loss of offsite power(LOOP) is a possible accident to any type of reactor, and this accident can reflect the main idea of reactor safety design. Therefore, it is very important to conduct a study on probabilistic safety assessment(PSA) of the molten salt reactor that is under LOOP circumstance. Purpose: The aim is to calculate the release frequency of molten salt radioactive material to the core caused by LOOP, and find out the biggest contributor to causing the radioactive release frequency. Methods: We carried out the PSA analysis of the LOOP using the PSA process risk spectrum, and assumed that the primary circuit had no valve and equipment reliability data based on the existing mature power plant equipment reliability data. Results: Through the PSA analysis, we got the accident sequences of the release of radioactive material to the core caused by LOOP and its frequency. The results show that the release frequency of molten salt radioactive material to the core caused by LOOP is about 2×10-11/(reactor·year), which is far below that of the AP1000 LOOP. In addition, through the quantitative analysis, we obtained the point estimation and interval estimation of uncertainty analysis, and found that the biggest contributor to cause the release frequency of radioactive material to the core is the reactor cavity cooling function failure. Conclusion: This study provides effective help for the design and improvement of the following molten salt reactor system.关键词：Molten salt reactor;Loss of offsite power(LOOP);Probabilistic safety assessment(PSA)
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发布时间：2021-03-05 - 摘要：Background: The proportion of nuclear power is gradually increasing in China’s energy structure. Purpose: On one hand, power grid and power plant coordination in the electricity grid system requires the nuclear power plants to adapt the needs of the peak regulation, frequence modification(FM), and even the grid AGC(Automatic Gain Control) mode. On the other hand, it is necessary to design a control system that can adapt the model G for the operation requirements, and ensure the safe and economic performance. Methods: With an experimental reactor as the research object and MATLAB/SIMULINK as test toolkit, we designed an improved the reactor power control system, and adopted three-loop PID(Proportional, Integral, Derivative) control system to ensure the precision control of a control rod. Results: The simulation results show that the method presented in the paper achieved better tracking performance and robustness. It can work against the unmeasurable disturbances. Conclusion: It is of practical significance for the reactor participating in the peak regulation of power grid, and the three-loop PID control system shows its improvement for reactor power control.关键词：Reactor power;Three-loop PID control;Control rod;Robustness;Disturbance
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发布时间：2021-03-05 - 摘要：Background: The calculation model of airborne radioactive source term in Nuclear Power Plants is one of the key points of safety review. However, in most safety analysis reports, a general simplified model of airborne radioactive source terms has been used, which is not applicable for all cases. Purpose: The aim is to complete the review calculations quickly and accurately. Methods: The model was based on the physical diffusion mechanism of radionuclides and their diffusion behavior in different spaces. Results: We proposed three models which could be respectively used for airborne radioactive source terms in reactor building, fuel element building and auxiliary building. Meanwhile, the key points in review of airborne radioactive source terms were put forward. Conclusion: Three models were proposed and their corresponding review key points will play a significant role in review calculations.关键词：Nuclear Power Plants;Airborne radioactive;Source terms;Model;Review
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发布时间：2021-03-05
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