核动力工程

Research on Physical Properties of Long Life Core Using Thorium-Uranium Fuel

Zheng Hongtao, Xia Bangyang, Xiao Peng, Li Songling

2015, 36(3): 1-5. doi: 10.13832/j.jnpe.2015.03.0001

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Abstract:
The neutronics characteristics of the square assembly that employs the homogenous thorium-uranium fuel have been analyzed and evaluated, and the numerical results show that the infinite multiplication factor of fuel assembly decreases more slowly with the increasing burnup. In other words, better reactivity performance could be provided, from the neutronics point of view, this is very good for the increasing of the reactivity control ability. On the basis of these above, the conceptual design of the long-life core using thorium-uranium fuel has been developed. The obtained physical design parameters show that its lifetime can reach up to 1000 equivalent full power days, the utilization ratio of ²³⁵U is 51.3%. The physical properties analyses presented that it is a very effective method to achieve the long-life core loading schemes for the use of thorium-uranium fuel in compact pressurized water reactors.

Study on Calculation of Ex-Core Detector Space Response Function by SN Adjoint Transport Method

Tan Yi, Tang Songqian, Zhang Hongyue, Ying Dongchuan, Xiao Feng, Li Lan

2015, 36(3): 6-9. doi: 10.13832/j.jnpe.2015.03.0006

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Based on the adjoint transport technology, the ex-core detector response function under the full power operation of one third-generation reactor is calculated by using the two-dimension SN code. Calculation results are compared with the original data, and the radial weighting factors would not exceed 3%, and the axial weighting factors would not exceed 1%.The result of this calculation proves that the calculation model and method is correct. The technology has been validated in the Ling’ao Phase II Nuclear Power Plant. Compared to the numerical result of the radial weighting factors via SN forward Transport Method, it shows that the calculation results difference of the two methods would not exceed 5%. It proves that the result for the two methods is identical and the computational efficiency of the Adjoint Transport Method is more efficient.

Scaling Distortions Analysis of Passive Residual Heat Removal System Test

Peng Chuanxin, Zan Yuanfeng, Zhu Xiaoli, Zhou Huihui, Zhang Yan, Zhuo Wenbin, Yan Xiao, Li Pengzhou

2015, 36(3): 10-14. doi: 10.13832/j.jnpe.2015.03.0010

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The Station Blackout Accidents（SBO） analysis is performed by CATHARE for passive reactor heat removal system（PRHRS） test facility and ACP100 respectively. The results show that the PRHRS test facility, which is designed according to the modified Ishii natural circulation scaling law, is capable of representing the thermal hydraulic parameters of prototype,and the scaling distortions are acceptable.

Investigation on Typical Lattice for Tight Arrangement Spiral-Fin Fuel Assembly

Li Minggang, Nie Changhua, Wang Jun, Yang Zumao, Xie Feng, Zhan Li, Wu Xiaofei, Huang Yanping

2015, 36(3): 15-19. doi: 10.13832/j.jnpe.2015.03.0015

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It is important in the reactor research and design to choose the typical lattice, which could represent the channel shape and thermal-hydraulic performance of the prototype assembly. In this study, the effect of bundle scale on thermal-hydraulic performance has been analyzed by numerical simulation method which applies to the tight arrangement spiral-fin fuel assembly.Simulation results show that compared with prototype assembly 217 rod bundle, cold wall effect and side wall effect of 19 rod bundle could be neglected. The deviations of equivalent diameter,pressure drop, center channel dimensionless mass flux and hot channel heat transfer coefficient are less than 13%. Therefore, 19 rod bundle are chosen to be the typical lattice for tight arrangement spiral-fin fuel assembly.

Experimental Investigation on Flow Resistance Coefficient for Tight Arrangement Spiral-Fin Fuel Assembly

Li Minggang, Xie Feng, Nie Changhua, Wang Jun, Yang Zumao, Zhan Li, Wu Xiaofei, Huang Yanping

2015, 36(3): 20-23. doi: 10.13832/j.jnpe.2015.03.0020

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Experimental investigation on flow resistance coefficient for the tight arrangement spiral-fin fuel assembly was performed. Results show that the inlet temperature has no effect on the flow resistance coefficient. The deviation between the proposed correlation and experimental data is less than 1%. A good comparison between Rehme correlation and experimental data was obtained when Reynolds number is small. Numerical simulation with BSL Reynolds stress turbulence model for the tight arrangement spiral-fin fuel assembly was carried out. Flow resistance coefficient,velocity distribution and secondary velocity were analyzed. The deviation is less than 8%. It shows that the CFD method could be used to predict the flow resistance coefficient for the tight arrangement spiral-fin fuel assembly.

Performance Test of a New Type Heat Exchange Tube with Internally Revolved Rib in Once-Through Steam Generator

Zhao Guozheng

2015, 36(3): 24-27. doi: 10.13832/j.jnpe.2015.03.0024

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Looking for high-performance and minimized heat exchange tube is one of the way for improving the performance of Once-through steam generator（OTSG）. This paper introduced the thermal-hydraulic experimental research on a new type heat exchange tube with internally revolved rib. The test system and the experiment model were presented. The heat transfer coefficient of the heat exchange tube and the influence of pitch on Nu were analyzed under different mass flow. The revolved rib showed a distinctive improvement on heat transfer performance under high Re condition, and minimizing the pitch was a good choice to enhance the heat exchange.

Analysis of Thermal Stratification Effect in Surge Line of Pressurizer in Nuclear Power Plants

Fan Shuchun, Wang Jianjun, Zheng Hongtao, Min Yuansheng

2015, 36(3): 28-30. doi: 10.13832/j.jnpe.2015.03.0028

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In this paper, the numerical simulation of the three dimensional flow fields is performed for the surge line of the nuclear power plant. The simulation incorporates the coupling effect between the solid pipes and the liquid coolant and the conjugate effect between the heat transfer and fluid flow. The basic structures of the flow field and the temperature distribution are obtained in the surge line under designed heat-up transient. Furthermore, the stress analysis Finite Element Analysis（FEA） model is established according to the structure features of the surge line.The model is used for the stress analysis of the surge line under corresponding transient.

Experimental Investigation of Supercritical Carbon Dioxide Natural Circulation in Rectangular Loop

Liu Guangxu, Huang Yanping, Wang Junfeng, Zan Yuanfeng, Lang Xuemei

2015, 36(3): 31-35. doi: 10.13832/j.jnpe.2015.03.0031

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Experiments were carried out in a rectangular loop to study the characteristics of supercritical carbon dioxide natural circulation. The influence of pressure and temperature difference on the mass flow rate was investigated and the effect of geometric of test loop was also preliminarily studied. Results show that no flow instability was found under the experimental condition. There was a peak for mass flow rate. Mass flow increased quickly before the peak point and decreased very slowly after the peak point. The effect of system pressure on mass flow rate was similar to subcritical natural circulation and higher mass flow rate was obtained in higher pressure.Temperature difference had vital effect on mass flow rate. Just small temperature difference between hot leg and cold leg could result in apparent change of mass flow rate. Geometric of test loop had vital effect on the characteristics of supercritical carbon dioxide natural circulation and more in-depth experimental research should be done to study it.

Transient Thermohydraulic Characteristics of HP-STMCs Space Reactor Core

Li Huaqi, Jiang Xinbiao, Yang Ning, Chen Lixin, hu Pan, Zhang Liang, Ma Tengyue, Zhu Lei

2015, 36(3): 36-40. doi: 10.13832/j.jnpe.2015.03.0036

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The power transient model and reactivity feedback model on transient thermohydraulic characteristics analysis of Heat Pipe Segmeuted Thermoelectric Module Converters（HP-STMCs） cooled space reactorcore were built by using CFD interface UDF, and the HPSR core transient analysis code SNPS-FTASR was developed and approved with steady state calculation. The transient response of HP-STMCs core was studied on reactivity-insertion accident transient and a heat pipe failed transient. The results show that the power and UN temperature increased rapidly, then the power and temperature increased slowly to a final new steady state because of the core reactivity temperature feedback. The new power is 121.3% rated power. When a heat pipe failed, the UN fuel temperature increased rapidly and a great negative reactivity was brought to the core, thus the HP-STMCs core underwent a rapid power decrease and finally operated at 88.7% rated power. The maximum temperature of UN fuel increased by 140 K. It is approved by the result that the HP-STMCs core is safety at transient state including reactivity-insertion accident and a heat pipe failed.

A Hydrodynamic Fragmentation Model Based on Boundary Layer Stripping Mechanism

Peng Cheng, Tong Lili, Cao Xuewu, Yan Xiao

2015, 36(3): 41-44. doi: 10.13832/j.jnpe.2015.03.0041

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Based on the boundary layer stripping mechanism, the hydrodynamic fragmentation process of fuel and coolant interaction（FCI） has been studied. With theoretical modeling and experimental correlation, semi-empirical equations which can predict the mass fragmentation rate and average size of fragments have been proposed. It can be intuitively referred from the equations that the relations between the hydrodynamic fragmentation process and the relative Weber numbers.The rationality of the equations is verified by comparing with typical experimental results. All the theoretical work is done for application in program development of FCI in the future.

Research of Effects of Accumulator on Loss-of-Coolant Accident for Small Modular PWRs

Gao Yingxian, Shen Yaou, Ceng Wei

2015, 36(3): 45-49. doi: 10.13832/j.jnpe.2015.03.0045

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In this study, based on the phenomena and characteristics of LOCA for the small modular PWRs, the mechanism for the occurrence of Peak Cladding Temperature（PCT） was analyzed, and the effects of accumulator（ACC） design on PCT and system depressurization were studied. It is shown that the accumulator injection may lead to more penalizing results for special medium size LOCA, and this result could be considered in the system design of small modular PWR.

Comparison of Chinese Criteria for Intervention in NPP Emergency Exposure Situations with IAEA Guideline

Yu Hong, Liu Yongmei

2015, 36(3): 50-53. doi: 10.13832/j.jnpe.2015.03.0050

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The Chinese criteria for protective action, intervention level, operational intervention level and off-site emergency zones are compared with IAEA guideline in the paper.The suggestions are put forward to implement the intervention in Chinese NPP emergency exposure situations.

Application of Emergency Operation Procedure in Establishing NPP Emergency Action Level

Yu Hong

2015, 36(3): 54-56. doi: 10.13832/j.jnpe.2015.03.0054

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Sometimes, the emergency operation Procedure implemented after the accident is related to the emergency IC and EAL. However, the basis of the emergency IC and EAL is the indications and parameters representing plant safety state, and the basis of the EOP is the events and accidents, and sometimes the indications and parameters is same in emergency IC and EAL and EOP, sometimes they are different in EAL and EOP. The correlations EOP with emergency classification level, recognition categories, IC and EAL are discussed and the application of EOP in establishing IC and EAL is proposed in the paper.

MSET＆SPRT-based Abnormal Condition Monitoring Technology for Nuclear Power Plants

Sun Yingjie, Peng Minjun

2015, 36(3): 57-61. doi: 10.13832/j.jnpe.2015.03.0057

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The on-line monitoring and forecasting techniques for the nuclear power plant reactor coolant system are studied. Based on the analysis of the characteristics of the reactor coolant system components and fault characteristics, multi-state variable estimation techniques（MSET） and sequential probability ratio technology（SPRT） was used to estimate and predict the system and to determine whether the system is abnormal. The anomaly can trigger a fault diagnosis unit or give warning. Test results show that MSET and SPRT combined technology make a good performance in the abnormal condition monitoring tasks.

Research of Pressure Control Based on Artificial Immune Control of Once-through Steam Generator

Cheng Shouyu, Li Cheng, Peng Minjun, Liu Xinkai

2015, 36(3): 62-65. doi: 10.13832/j.jnpe.2015.03.0062

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The paper proposes a new control strategy to apply in the field of pressure controller of once-through steam generator. The strategy is distributed and multiple input and output coupling Artificial immune control strategy which is based the thought of decentralized control of the distributed control system, the immune mechanism of B-cell co-operating with T-cell, and the biological immune mechanism of antigens and antibodies interacting. In order to verify the control strategy, simulation experiment has been carried out in a simulator of fast reactor. The simulation results show that the new control strategy has small overshoot and shorter steady time compared with conventional PID control strategy, and it can effectively improve the dynamic operating characteristics of pressure and related parameters of once-through steam generator.

Technique of Smoothing Spectrum Data Based on Adaptive Filter

huo Jianwen, Wang Heng, Zhou Zhiru, Zhang Hua, HE Kan, Zhang Yan

2015, 36(3): 66-69. doi: 10.13832/j.jnpe.2015.03.0066

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By using the traditional spectral line smoothing methods, improper filter parameter settings or a high frequency of smoothing will cause the spectral line distortion. To address this problem, the fast Kalman filter is used to implement the recursive least squares method according to the adaptive filtering principle. The forward and backward predictors are used to update the filter parameters to denoise and smoothen the energy spectrum data. Experiments are carried out to quantitatively compare and set up to analyze the proposed method with the least squares polynomial approximation method and the least mean-squares algorithm. The experimental results show that the proposed method can effectively reduce the noise in the energy spectrum while retaining the features of energy spectrum.

Study on Theory and Application of Kass-Steffey Adjustment for Parameter Estimation of PSA

Chen Yan, Zheng Peng, Li Chaojun, Zhu Wei, SHi Qiang, Zhang Chunming

2015, 36(3): 70-74. doi: 10.13832/j.jnpe.2015.03.0070

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Reliability data is the basis of probabilistic safety assessment in NPPs. The parametric empirical Bayes models would underestimate the uncertainty of estimated parameter in the case with few failure data. Kass-Steffey adjustment could use Taylor series expansion to correct the posterior variance. The Kass-Steffey adjustment were derived in detail, and taking the initiating events as an example, the posterior variance and 90% credible interval are calculated. It is found that the Kass-Steffey adjustment is unimportant if there are many failure data, while it is noted that the Kass-Steffey adjustment is very important when there are few failure data, which make the posterior variance change 16%~99%, and credible interval change 4%~53%.

Application of A Method Combining Markov and Convolution in PSA

Deng Chunrui, Yu Hongxing

2015, 36(3): 75-79. doi: 10.13832/j.jnpe.2015.03.0075

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A method combining Markov and convolution is provided in this paper. The power recovery scenario after station blackout is used to demonstrate the method in detail. The analysis results show that the method can efficiently solve the time interdependence issue, thus eliminating unnecessary conservatism in PSA model, and meanwhile, the method can take maintenance strategies into account easily.

Hydraulic Analysis and Design Improvement for Main Check Valve under Non-Uniform Flow

Tan Shuyang, Chen Jiu, Guan Li, Zhao Xuecen, Huang Wei, Cheng Xiang

2015, 36(3): 80-83. doi: 10.13832/j.jnpe.2015.03.0080

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CFD software is applied to analyze the hydraulic characteristics on the main check valve flow model about multi-loop reactor. The outlet non-uniform flow of reactor coolant pump is used to calculate the hydraulic moment of the valve under the full-open condition. By analyzing the key structure factors and its effect on the hydraulic characteristics, the valve configuration was optimized. The results from the improved model show that the pressure drop through flow near the inlet and outlet region has been reduced, and the position of disc has been kept the whole opening,which could avoid the effect of pump-valve coupling operation.

Study on Vibration Characteristics of Three Bearing Supporting Main Coolant Pump

Yang Zhang

2015, 36(3): 84-87. doi: 10.13832/j.jnpe.2015.03.0084

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Based on the running experience for 100 D Main Coolant Pump, its typical abnormal vibration phenomena is studied, and a vertical rotor-bearing system dynamics theory is established to analyze the vibration characteristics of the rotor. It can conclude that as for the conference of vertical construction, three bearing supporting structure and watered guide bearing, when the running condition is stable, the vibration state is stabilized, when the running condition is influenced by the circumstance disturbance or in transient state, the vibration will be instabilized and the vibration trend will change in a nonlinear character. In order to maintain a stable running condition,a fine balance test should be done to reduce the vibration value of the main coolant pump as low as possible.

Analysis and Improvement of Control Logic for Entrance Isolation Valve in RRA System

Fang Huasong, Liu Shili, Zhang Jinfei, Li Jianwen

2015, 36(3): 88-89. doi: 10.13832/j.jnpe.2015.03.0088

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Because of the origin design for control logic of entrance isolation valve in RRA system was not conform to the single failure criterion, the improvement scheme, which would be added two sets of pressure transmitter, has been raised. The effect of RRA system and the damage of reactor core have been evaluated through quantitative calculation about the scheme of the modification.

Analysis and Optimization of Kinematic Pair Force in Control Rod Drive Mechanism

Sun Zhenguo, Liu Sen, Ran Xiaobing, DAi Zhangnian, Li Yuezhong

2015, 36(3): 90-93. doi: 10.13832/j.jnpe.2015.03.0090

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Function expressions of kinematic pair force with latch dimensions, friction coefficient, link angle and external load was obtained by theoretical analysis, and the expression was verified by the motion analysis software. Key parameters of kinematic pair were confirmed,and their effect trends with force of parts were obtained. They show that the available method of kinematic pair optimization is increasing the space of latch holes. Using the motion analysis software,the forces of parts before and after optimization was compared. The result shows that the forces of parts were improved after the optimization.

Numerical Analysis of All Flow State Lubrication Performance of Water-Lubricated Thrust Bearing

Deng Xiao, Deng Liping, Huang Wei, Liu Lizhi, Zhao Xuecen, Liu Songya

2015, 36(3): 94-98. doi: 10.13832/j.jnpe.2015.03.0094

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A model enabling all different flow state lubrication performance simulation and analysis for water-lubricated thrust bearing is presented, considering the temperature influence and elastic deformation. Lubrication state in the model is changed directly from laminar lubrication to turbulent lubrication once Reynolds number exceeds the critical Reynolds number. The model is numerically solved and results show that temperature variation is too little to influence the lubrication performance; the elastic deformation can slightly reduce the load carrying capacity of the thrust bearing; and the turbulent lubrication can remarkably improve the load carrying capacity.

Experimental Study and DEM Simulation of Granular Flow through a New Sphere Discharge Valve

Zhang He, Li Tianjin, Huang Zhiyong, Gao Zhi, Qi Weiwei, BO Hanliang

2015, 36(3): 99-102. doi: 10.13832/j.jnpe.2015.03.0099

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Experiments and DEM simulation have been conducted to investigate the granular flow through a new type of sphere discharge valve. The new sphere discharge valve was based on the principle of angle of repose. The glass sphere was used in the granular discharge experiments.Experimental results showed that the relation between the averaging sphere discharge mass flow rate and the stroke of the sphere discharge valve were consisted of three zones, i.e. the idle stroke zone, linearly zone and orifice restriction zone. The Beverloo’s law was suitable for the granular flow through multi-orifices in the orifice restriction zone. The variation of averaging sphere discharge mass flow rate with the stroke of the sphere discharge valve was described by Beverloo’s law with the modification based on the stroke of the sphere discharge valve. DEM simulation results showed that the drained angle of repose during granular flow in the sphere storage vessel remained 23 degrees with different stroke of the sphere discharge valve.

Design of Sample Analysis Device for Iodine Adsorption Efficiency Test in NPPs

Ji Jinnan

2015, 36(3): 103-105. doi: 10.13832/j.jnpe.2015.03.0103

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In nuclear power plants, iodine adsorption efficiency test is used to check the iodine adsorption efficiency of the iodine adsorber. The iodine adsorption efficiency can be calculated through the analysis of the test sample, and thus to determine if the performance of the adsorber meets the requirement on the equipment operation and emission. Considering the process of test and actual demand, in this paper, a special device for the analysis of this kind of test sample is designed.The application shows that the device is with convenient operation and high reliability and accurate calculation, and improves the experiment efficiency and reduces the experiment risk.

Commission of Reactor Coolant Pump in Fangjiashan NPP

Zhou Zhiwen, Weng Yunfeng, Liao Xiangling, Song Zhengchi

2015, 36(3): 106-109. doi: 10.13832/j.jnpe.2015.03.0106

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The RCP of Fangjiashan NPP is much different with that in other nuclear power plants in China. This paper firstly introduces the generational of RCP, then expound the problems and ways in commission. The main problems, such as the large vibration of pump shaft, the maladjustment of main coolant pump logic on site and the problems of shaft seal and the oil system,are analyzed and discussed with the technicians and system designers, and solved.

Study on Application of Enriched Boric in Primary Coolant of Nuclear Power Plants

Liu Jinhua, Wen Juhua, Gong Bin, Xia Xiaojiao, Jiang E, Zhao Yongfu, Zhou Zhiru

2015, 36(3): 110-113. doi: 10.13832/j.jnpe.2015.03.0110

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Nuclear power plants gradually adopt the long-term fuel cycle, the power density of the reactors is increasing and the level of burnup is higher. It is more complex and difficult to control the primary coolant chemistry. The water chemistry of enriched boric acid in primary coolant was calculated. Results show that the use of EBA for 40% enrichment can reduce the initial concentration of boron and improve the p H value of primary coolant, enabling the core of reactor to operate at p H^300℃7.2 to 7.4.

Research on Problem of Radioactive Iodine Activity Monitor False Alarm

Guo Peibin

2015, 36(3): 114-116. doi: 10.13832/j.jnpe.2015.03.0114

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False alarm problem of radioactive iodine activity monitor during commissioning in nuclear plant is analyzed and studied. Results show that the instrument background noise, ambient gamma radiation field and other non nuclide measurement statistics will cause the measured value distortion; the using of the ¹³¹I detecting efficiency to calculate the ¹³¹I to ¹³⁵I total radioactive iodine volume activity will cause the distortion of the measured results. Through the analysis of the reasonability of the set area of the radioactive iodine monitor energy window, and to change the measurement window energy 100~2000 ke V to 310~410 ke V, only ¹³¹I is monitored. After the implementation of this program, the instrumentation values are accurate and no false alarm occurs.

Research on Blowing Technology for Secondary Side in HTR-PM Steam Generator

Liu Junfeng, Li Kang, Ma Xiaolong

2015, 36(3): 117-119. doi: 10.13832/j.jnpe.2015.03.0117

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Based on the cleaning of the secondary side in High-Temperature Gas-cooled Reactor（HTR-PM） steam generator. the compressed air blowing technology are proposed in this paper. Through the analysis on the flow behavior of steam-water two-phase or one-phase in helical coils of the secondary side in the steam generator,the method of blowing coefficient was introduced.According to the design parameters of the unit, the result showed that the compressed air blowing technology is feasible.

Feasibility Analysis for Increasing Purification Flowrate during Plant Shutdown Oxygenation

Wang Zhixiao

2015, 36(3): 120-124. doi: 10.13832/j.jnpe.2015.03.0120

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Using RCV system hydraulic model, the feasibility of increasing purification flowrate during plant shutdown oxygenation of M310 units is analyzed, and a basic engineering modification for this item is provided. The result indicates that the purification flowrate increase from 27.2 m³/h to 40 m³/h, and it can save two hour at least in every maintenance period of the 1000 MW nuclear power unit.

Chemical Effect Evaluation of Containment Sump Filter of CPR1000 Nuclear Power Plants

Li Jieyao, Tang Hui, Zhao Yanhui, Luo Mingkun, Wang Qingli, Wang Zhengguang

2015, 36(3): 125-128. doi: 10.13832/j.jnpe.2015.03.0125

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The chemical effects for the recirculation sump filter blockage of CPR1000 Nuclear Power Plant（NPP） under Loss of Coolant Accident（LOCA） is studied. In chemical effects evaluation, simulation experimentation is adopted. The result indicates that the effect of chemical effect on the emergency recycle is slight in CPR1000 NPP.

Feasibility Study on Application of Passive Safety System in Fusion-Fission Hybrid Energy Reactor

Yu Zhangcheng, Jie Heng

2015, 36(3): 129-134. doi: 10.13832/j.jnpe.2015.03.0129

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The passive safety system was applied to the fusion-fission hybrid energy reactor and a RELAP5 model was developed to represent the primary loop, partial secondary loop and the passive safety system components. The transient calculation and research were conducted for stuck pump accident, the SBLOCA on cold leg. The results indicate that the passive safety system can ensure the safety of fusion-fission hybrid energy reactor in the selected reactor accidents and it is feasible to apply the passive safety system to fusion-fission hybrid energy reactor. The decay heat can be exported effectively while the flow area of the heat exchanger of the PRHRs was optimized.Increasing the volume of CMT is of great significance for the reactor safety margin.

Assessment of In-Vessel Retention for Advanced Large Size PWRs

Jin Yue, Bao Han, Liu Xiaojing, Cheng Xu

2015, 36(3): 135-141. doi: 10.13832/j.jnpe.2015.03.0135

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In-Vessel Retention-External Reactor Vessel Cooling（IVR-ERVC） is a key severe accident management strategy, and the present assessment method on the effectiveness of IVR is mainly based upon the lumped parameter（LP） model. With related regulations considered, four severe accident scenarios were selected and calculated using MAAP4 codes to determine the probability distribution functions of input parameters needed in the assessment process. And the feasibility of the IVR-ERVC strategy for large size PWRs is determined to be potentially higher than 98% by using a lumped parameter analysis code. In the end, considering the impact of the input parameters, recommendation for the designs of reactor core internals has been proposed.

3D Laser Doppler Measurement on Turbulent Flows in a 3×3 Rod Bundle

Yu Yang, XIong Jinbiao, Cheng Xu

2015, 36(3): 142-144. doi: 10.13832/j.jnpe.2015.03.0142

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Turbulent flows in a rod bundle are important field for the nuclear reactor fuel assembly since the flow mixing in a sub-channel or between sub-channels can significantly modify the heat transfer performance. A five beam three dimension Laser Doppler Velocimetry（LDV）system is applied to measure the flow velocities in a 3×3 rod bundle installed with the simple grid spacers and without mixing vanes. The rod diameter and spacing between rods are set according to the typical fuel assembly. The area to be measured is near the outlet of the bundle, and it is far from the space grid, so it can be treated as the developed flow condition. 2D LDV is used to measure one quart of the flow cross-section, and the main velocity and main turbulence intensity have been recorded.

Experimental Investigation of Natural Circulation in a Symmetrical Loop under Large Scale Rolling Motion Conditions

Zhu Hongye, Yang Xingtuan, Sun Yanfei, Jiang Shengyao

2015, 36(3): 145-147. doi: 10.13832/j.jnpe.2015.03.0145

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Natural circulation characteristics in symmetrical loops under rolling condition were investigated theoretically and experimentally. Rolling experiments with a zero power load show that angular acceleration causes the fluctuation in branch flow channels, but has no influence on the middle channel. Full power experiments under rolling condition exhibited observable flow rate and temperature oscillations in each branch of the flow channel. The fluid oscillations in the side flow channels had the same period and phase with the rolling angle, while the fluid in the middle channel oscillates with half the rolling period.

Effect of Marine Condition on Feature of Natural Circulation after Accident in Floating Nuclear Power Plant

Yang Fan, Zhang Dan, Tan Zhanglu, Ran Xu, Yu Hongxing

2015, 36(3): 148-151. doi: 10.13832/j.jnpe.2015.03.0148

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The incline and swing effect on natural circulation of floating nuclear power plant under site black out（SBO） accident is studied using self-developing marine condition system code RELAP5/MC. It shows that,for floating nuclear power plant under marine condition, the pressurizer fluctuating flow rate, the parallel heat sink（steam generator） have significant influences on the direct passive reactor heat removal（PRHR） system, which is different from other secondary PRHR under marine condition. The flow exchange between the loop and the pressurizer have major effect on cooling capacity for the left side loop.

Parallel Strategies and Verification of Sensitivity Analysis Function of RMC Code

Qiu Yishu, Liang Jingang, Yu Jiankai, Wang Kan

2015, 36(3): 152-156. doi: 10.13832/j.jnpe.2015.03.0152

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In order to improve the computational efficiency and reduce the memory usage of the function in the Reactor Monte Carlo code RMC to compute the effective multiplication factor（keff） sensitivity coefficients with regard to nuclear data, two parallel strategies which are based on two ways to estimate the adjoint flux, namely, the next generation neutron number estimator and the neutron production rate estimator, are implemented in RMC. A multi-group infinite-medium test and a continuous-energy test are used to verify the new strategies. Results show that the sensitivity coefficients computed by the two parallel strategies agree well with the analytic solutions and those computed by MCNP6. Furthermore, the new strategies run 3 times as fast as MCNP6 and the figure of merits of the new strategies to compute the sensitivity coefficients to total cross section of different isotopes are 4 to 8 times as high as MCNP6.

Neutron Transport Study Based on Assembly Modular Ray Tracing MOC Method

Tian Chao, Zheng Youqi, Li Yunzhao, Li Shuo, Chai Xiaoming

2015, 36(3): 157-161. doi: 10.13832/j.jnpe.2014.03.0157

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It is difficulty for the MOC method based on Cell Modular Ray Tracing to deal with the irregular geometry such as the water gap between the PWR lattices. Hence, the neutron transport code NECP-Medlar based on Assembly Modular Ray Tracing is developed. CMFD method is used to accelerate the transport calculation. The numerical results of the 2D C5G7 benchmark and typical PWR lattice prove that NECP-Medlar has an excellent performance in terms of accuracy and efficiency. Besides, NECP-Medlar can describe clearly the flux distribution of the lattice with water gap.

Analysis and Comparison of Pebble Flow Dynamics in 1 m and 2 m Two-Dimensional Experimental System with Marking Pebble Method

Jia Xinlong, Yang Xingtuan, GUi Nan, Tu Jiyuan, Jiang Shengyao

2015, 36(3): 162-166. doi: 10.13832/j.jnpe.2015.03.0162

Abstract(9) PDF(0)

Abstract:
To study the height effect of the pebble flow dynamics, a 2-D pebble-bed experimental system for High Temperature Gas-cooled Reactor（HTGR） has been established based on the similarity criteria to study the pebble flow by using the marking pebble method. The characteristics of mean stream line, inner flow distribution, mean stagnant time, and distribution of the pebbles in the mixing zone of the 1m and 2m experimental system have been discussed and compared. The results show that the mean streamline is smooth and symmetrical and the flow characteristics in the side area and the central region are greatly different. The pebble flow in the lower zone of the experiment set is more nonuniform than that in the upper zone. The degree of dispersion can be enlarged by increasing the height of the bed. These results validate the Gaussian Probability Distribution of pebble in the mixing zone. The moving area of the marking pebble has a wide middle section and narrow head and end sections. The degree of dispersion is larger in the higher bed than that in the lower bed.

Effect of Sn on Compressive Creep Behavior of AgInCd

Chen Le, Xiao Hongxing, Liang Bo, Long Chongsheng

2015, 36(3): 167-171. doi: 10.13832/j.jnpe.2015.03.0167

Abstract(9) PDF(0)

Abstract:
The Compressive creep behavior of as-cast Ag In Cd alloy with and without tin（Sn, 3wt%） was investigated by using the special modified apparatus on RDL50 creep tester at 300~400℃and compressive stress was in the range of 12~30 MPa.The relationship among temperature, stress and steady strain rate has been analyzed, the stress exponent n and apparent activation energy Q_a of the creep process have been calculated as well as the mechanism of compressive creep behavior have been discussed, based on the TEM images of microstructure. The results showed that, the steady strain rate of the alloy increased with the increasing of temperature and compressive stress.Compared with Ag In Cd, the stress sensitivity became more obvious and Q_a increased in each stress with the tin in it, indicating that the creep resistance of Ag In Cd Sn was better. The n of Ag In Cd were3.31, 4.09 and 5.77 under the 300℃,350℃,400℃ respectively, while of Ag In Cd Sn were 9.41,8.07 and 9.48. The Q_a of Ag In Cd were 68.1, 103.7, 131.6 k J/mol under 12, 18, 24 MPa, for Ag In Cd Sn, namely 147.9, 126.9, 149.9 k J/mol. There were lots of stacking faults in the TEM images under each creep condition, which played a critical role in the creep mechanism. Mechanical twinning was the main mechanism at 300 ℃ while dislocation climbing was the dominant mechanism at 400℃.

2015 Vol. 36, No. 3