Evaluation of check valve monitoring methods

Check valves are used extensively in nuclear plant safety systems and balance-of-plant (BOP) systems. Their failures have resulted in significant maintenance efforts and, on occasion, have resulted in water hammer, overpressurization of low-pressure systems and damage to flow system components. Consequently, in recent years check valves have received considerable attention by the Nuclear Regulatory Commission (NRC) and the nuclear power industry. Oak Ridge National Laboratory (ORNL) is carrying out a comprehensive two phase aging assessment of check valves in support of the Nuclear Plant Aging Research (NPAR) program. As part of the second phase, ORNL is evaluating several developmental and/or commercially available check valve diagnostic monitoring methods; in particular, those based on measurements of acoustic emission, ultrasonics, and magnetic flux. These three methods were found to provide different (and complementary) diagnostic information. The combination of acoustic emission with either ultrasonic or magnetic flux monitoring yields a monitoring system that succeeds in providing sensitivity to detect all major check valve operating conditions. The three check valve monitoring methods described in this paper are still under development and are presently being tested as part of a program directed by the Nuclear Industry Check Valve Group (NIC) in conjunction with the Electric Power Research Institute (EPRI). Phase 1 of this program (water testing) is being carried out at the Utah Water Research Laboratory located on the Utah State University campus.     

Hydrodynamic characterization and optimization of Contra-push check valve by numerical simulation

This paper introduced the structure and working principle of a new designed check valve, Contra-push check valve (CPCV), which can release water hammer and valve slam in accidents and special working status of nuclear power systems. The steady and transient characteristics of CPCV are simulated by CFD codes. Based on the experimental data, it is shown that the result is highly dependent on the turbulence model. The renormalization group theory (RNG) k–ε model is proved to be more accurate to describe the flow inside the valve. Steady hydraulic characteristics computed with RNG k–ε model agreed well with the experimental data at different positions of the plug. The Sensitivity analysis of structure parameters of CPCV were carried out in this study and two key factors were revealed.     

Design and analysis of direct action solenoid valve based on computational intelligence

Control Rod Hydraulic Drive Mechanism (CRHDM) is a newly invented patent of the Institute of Nuclear and New Energy Technology Tsinghua University which owns CRHDM's independent intellectual property rights while the integrated valve made up of three direct action solenoid valves is the key part of this mechanism. Therefore, the performance of the solenoid valve affects the integrated valve and the CRHDM directly. In this paper, we present a method to design the parameters of the direct action solenoid valve based on orthogonal experiment design, back propagation (BP) neural network and particle swarm optimization (PSO). The result proves that the method is feasible and accurate to design the parameters in order to obtain the biggest electromagnetic force. Besides, the result also shows that it is the current which influences the electromagnetic force of the direct action solenoid valve most.     

Preliminary design and performance study of EAST liquid lithium limiter based on CPS

Lithium has the ability of H recycling suppression and impurities absorption and it can be used as plasma facing material (PFM) in tokamaks. Lithium conditioning experiments were launched on EAST, HT-7 and some other tokamaks for many years by using the methods of GDC, IRCF and evaporation. Liquid lithium has better performances in effective lifetime and heat removal aspects compared to non-liquid lithium. While, applying liquid lithium in the tokamak would cause the safety problem as the lithium can react with many substances violently and the magnetohydrodynamic behavior is difficult to be handled. EAST liquid lithium limiter (LLL) system is under developing and will be applied in EAST to study the main technologies of the liquid lithium application. The normal operation temperature of the limiter is expected as 230–550 °C under the active cooling of water. Capillary porous system (CPS) is used to prevent the lithium from splashing under large electromagnetic force by increasing the surface tension of the lithium. In order to investigate the cooling performance of the cooling design, the thermal-hydraulic analysis was done which shows that with 3 m/s flowing velocity, the water can keep the limiter under 550 °C all the time if the heat flux is lower than 0.7 MW/m². Under heat flux of 1 MW/m², the limiter should be retreated within 7 s to avoid erosion. The pressure drop of the coolant under 3 m/s is less than 40 kPa with temperature difference nearly 34 °C which meet the design requirements very well. The key manufacture process and technologies like vacuum bonding between the CuCrZr heat sink and 316L guide plate were well studied in the R&D process. The heating test on the test bench showed that the CPS can be heated efficiently by the heaters attached into the heat sink.     

Theoretical and experimental performance analysis for cold trap design

Cold trap is a purification unit used in sodium system of FBR's for maintaining the oxygen/hydrogen level in sodium within acceptable limits. It works on the principle of crystallization and precipitation of oxides/hydrides of sodium in a wire mesh, when the temperature of sodium is reduced below the saturation temperature. The cold traps presently used have lower effectiveness and get plugged prematurely. The plugged cold traps are cleaned and then put back into service. Frequent cleaning of cold trap results in the long down time of the sodium system. New design of cold trap has been conceived to overcome the above problems. The mathematical modeling for the new design was carried out and validated with experimentally tested results for its effectiveness. This paper shares the experience gained on the new design of cold trap for FBR's.     

An intelligent human-machine system based on an ecological interface design concept

It seems both necessary and promising to develop an intelligent human-machine system, considering the objective of the human-machine system and the recent advance in cognitive engineering and artificial intelligence together with the ever-increasing importance of human factor issues in nuclear power plant operation and maintenance. It should support human operators in their knowledge-based behaviour and allow them to cope with unanticipated abnormal events, including recovery from erroneous human actions. A top-down design approach has been adopted based on cognitive work analysis, and (1) an ecological interface, (2) a cognitive model-based advisor and (3) a robust automatic sequence controller have been established. These functions have been integrated into an experimental control room. A validation test was carried out by the participation of experienced operators and engineers. The results showed the usefulness of this system in supporting the operator's supervisory plant control tasks.     

Design and test of hydraulic vacuum breaker check valve for simplified boiling water reactor

In the current design of the simplified boiling water reactor, the vacuum breaker check valve is an important safety component. The vacuum breaker check valve is the only key safety components which is not passive in nature. Failure of this mechanical valve drastically reduces the passive containment cooling system cooling capability and hence containment pressure may exceed the design pressure. To eliminate this problem novel vacuum breaker check valve was developed to replace the mechanical valve. This new design is based on a passive hydraulic head, which is fail-safe and is truly passive in operation. Moreover this new design needs only one additional tank and one set of piping each to the wetwell and drywell. This system is simple in design and hence is easy to maintain and to qualify for operation. The passive vacuum breaker check valve performance was first evaluated using RELAP5. Then the passive vacuum breaker check valve was constructed and implemented in the PUMA integral test facility. Its performance was studied in a large break loss of coolant accident simulation test performed in PUMA facility.     

Development of a swing check valve model for a low velocity pipe flow prediction

A swing check valve is commonly used to prevent a reverse flow in the pipe lines of a nuclear power plant. The flow resistance by the swing check valve varies with the location of the swing disk in the velocity range lower than the required minimum velocity for a full opening of the swing disk, thereby the fluid flow is significantly affected by the dynamic motion of the swing disk. Such a phenomenon is very important to analyze safety issues, one of which is the gravity feed following a loss of the residual heat removal (RHR) which occurs during a mid-loop operation. This paper focused on the development of a new check valve model to enhance the capability of the thermal-hydraulic system code. A new angular momentum equation for the disk of a swing check valve is proposed. The proposed model is implemented into the MARS code and verified through a comparison of the simulation results with the experimental data. In particular, the results of the simulation for the gravity feed line are comparably consistent with the real test data performed in a nuclear power plant.     

Dynamic load effects on gate valve operability and snubber performance

The Idaho National Engineering Laboratory (INEL) participated in an internationally sponsored seismic research program conducted at the decommissioned Heissdampfreaktor (HDR) located in the Federal Republic of Germany. An existing piping system was modified by installation of 200-mm, naturally aged, motor-operated gate valve from a U.S. nuclear power plant and a piping support system of U.S. design. Using various combinations of snubbers and other supports, six other piping support systems of varying flexibility from stiff to flexible were also installed and tested. Additional valve loadings included internal hydraulic loads and, during one block of tests, elevated temperature. The operability and integrity of the aged gate valve and the dynamic response of the various piping support systems were measured during 25 representative simulations of seismic events.     

基于LABVIEW和数字多道脉冲幅度分析器的γ能谱分析软件的开发

基于LABVIEW平台和数字多道脉冲幅度分析器开发了γ能谱分析软件,能实现谱数据光滑、自动寻峰、能量刻度、峰边界道的确定和峰面积的计算,从而完成对γ能谱的定性和定量分析.应用LABVIEW中CIN节点与C语言的结合实现了查找元素的功能.该谱分析软件已用于数字多道脉冲幅度分析器(DMCA)中对γ能谱数据进行分析,可以实现基本的谱分析功能.     

Development of diagnosis algorithm for the check valve with spectral estimations and neural network models using acoustic signals

We have developed a method for detecting and diagnosing a disk wear failure and a foreign object failure among the various failure modes of check valves. The method is based on the acoustic emission sensors which can detect the sound wave of the leakage flow and the estimation of the power spectral densities with an auto-regressive model. For validating the method, we implemented a hydraulic test loop with an artificially failed check valve. We have found that the frequency spectrums from the acoustic signals are strongly dependent on the failure modes of the check valve and that they are nearly independent of the failure size and operating pressure through an estimation of the power spectral density with an auto-regressive signal processing model. In addition, the root mean square values of the acoustic signal and the amplitudes of the power spectral density as well as the loop pressure have a strong dependency on the failure size in each failure mode of the check valve. We developed a diagnosis algorithm by using neural network models in order to identify the type and size of the failure in the check valve. The diagnosis algorithm consists of a hierarchical model composed of three back-propagation neural networks. The results of our research and the experiments show that the diagnosis algorithm is proven to be a good solution for identifying the failures of the check valves without any disassembling work.     

Analysis of the effect of lubrication performance on motor operated valve actuator output thrust

In this study, we performed theoretical analysis and test to identify an effect that lubricant performance has on actuator output thrust of MOV. Particularly, we introduced Stem Friction Coefficient (SFC) concept that means friction coefficient between a stem nut and a stem screw. By using SFC concept, an effect of lubricant performance on the actuator output thrust was analyzed quantitatively. The first phase test was performed to compare the lubrication performance between new lubricant and old lubricant and the second phase test was performed to compare the lubrication performance for the three kinds of representative lubricants (EP0, EP1, EP2) being used in Korea nuclear power plants. According to the test results, SFC value of old lubricant appeared higher than that of new lubricant and a old lubricant at TST point generated lower thrust value than a new lubricant at the same torque value. We can verify that the effect of lubrication performance has on power generated in an actuator was very large and SFC was a very useful variable in analyzing lubrication performance quantitatively.     

MS Windows定时器性能分析及在定时-计数系统设计中的应用

通过对MS Windows定时器性能的测试和分析，利用多媒体定时器精度分布的特点，采用“合成定时-选择计数”方法获得预定精度定时，在放射测量定时-计数系统中应用。     

CMOS集成电路的闭锁特性和闭锁窗口分析

由于布局结构的复杂性,CMOS集成电路可能存在多个潜在的寄生闭锁路径。各个闭锁路径因触发剂量率和闭锁维持电压、闭锁维持电流不同而相互影响．可能产生一个或多个闭锁窗口。在详细分析CMOS集成电路闭锁特性的基础上．建立了“三径”闭锁模型,对闭锁窗口现象进行了合理解释。     

Preliminary performance analysis and optimization based on 1D neutronics model for Indian DEMO HCCB blanket

India, under its breeding blanket R&D program for DEMO, is focusing on the development of two tritium breeding blanket concepts; namely the lead-lithium-cooled ceramic breeder and the helium-cooled ceramic breeder (HCCB). The study presented in this paper focuses on the neutronic design analysis and optimization from the tritium breeding perspective of the HCCB blanket. The Indian concept has an edge-on configuration and is one of the variants of the helium-cooled solid breeder blanket concepts proposed by several partner countries in ITER. The Indian HCCB blanket having lithium titanate (Li₂TiO₃) as the tritium breeder and beryllium (Be) as the neutron multiplier with reduced-activation ferritic/martensitic steel structure aims at utilizing the low-energy neutrons at the rear part of the blanket. The aim of the optimization study is to minimize the radial blanket thickness while ensuring tritium self-sufficiency and provide data for further neutronic design and thermal-hydraulic layout of the HCCB blanket. It is found that inboard and outboard blanket thicknesses of 40 cm and 60 cm, respectively, can give a tritium breeding ratio (TBR) >1.3, with 60% ⁶Li enrichment, which is assumed to be sufficient to cover potential tritium losses and associated uncertainties. The results also demonstrated that the Be packing fraction (PF) has a more profound impact on the TBR as compared to 6Li enrichment and the PF of Li₂TiO₃.     

晶体表面特性对PET探测器性能的影响

<正>电子发射断层成像(Positron Emission Tomography,PET)作为最灵敏和具有定量测量能力的功能分子影像技术,越来越广泛地应用于生物医学研究,如疾病的动物模型、新药物的研发和新治疗方法的评估等。提高探测器的性能是改进PET仪器性能的关键,PET探测器通常由分割的闪烁晶体阵列和光探测器组成,文中使用位置灵敏光电倍增管和不同晶体表面特性的硅酸钇镥((Lu,Y)2Si O5,LYSO)晶体阵列,对新型的双端读出三维PET探测器和传统的单端读出二维PET探测器的性能进行了测量。实验结果表明,对于双端读出PET探测器,两种晶体阵列提供相近的晶体分辨图和能量分辨率,但非抛光晶体阵列提供好的深度分辨率,双端读出PET探测器需要使用表面不抛光的晶体阵列;对单端读出PET探测器,抛光晶体阵列提供好的晶体分布图和能量分辨率,单端读出PET探测器需要使用表面抛光的晶体阵列。     

An experimental validation of the guideline for inelastic design analysis through structural model tests

In this paper, the inelastic analysis procedures recommended to use in the advanced elevated temperature structural design guide under development in Japan for the improved design of future fast breeder reactors were validated through the structural model tests and the evaluation of the experimental results by the inelastic analyses. First, a thermal fatigue test of a 316FR hollow cylinder with two longitudinal weldments was conducted under the condition of combined constant axial load and cyclic movement of axial temperature distribution, which simulated the loading condition near the free surface of coolant sodium in the main vessel of fast breeder reactors (FBRs). In the experiments, longitudinal and radial ratcheting deformation were measured and crack initiation life was also examined. Second, the inelastic analyses were carried out in accordance with the recommended procedure by using the measured results of oscillating temperature distribution. Finally, the results of inelastic analyses were compared with the experimental results and it was validated that the recommended practice gave a conservative result for the deformation and a good estimation of strain range for the fatigue life evaluation.     

基于嵌入式Linux的SPECT探头系统设计

设计了一套基于嵌入式Linux的单光子发射计算机断层成像(SPECT)探头系统。该系统硬件由探测器模块、数据采集模块、ARM微处理模块、网络接口模块和人机接口模块等几大模块组成。系统软件采用嵌入式Linux,并使用多线程技术。可以实现高速数据采集、实时数据校正和网络化数据通信,从而提高采集速率,减少系统死时间,提高系统的智能化和稳定性。     

Influence of thermal performance on design parameters of a He/LiPb dual coolant DEMO concept blanket design

Spanish Breeding Blanket Technology Programme TECNO_FUS is exploring the technological capabilities of a Dual-Coolant He/Pb15.7Li breeding blanket for DEMO and studying new breeding blanket design specifications. The progress of the channel conceptual design is being conducted in parallel with the extension of MHD computational capabilities of CFD tools and the underlying physics of MHD models. A qualification of MHD effects under present blanket design specifications and some approaches to their modelling were proposed by the authors in [1]. The analysis was accomplished with the 2D transient algorithm from Sommeria and Moreau [2] and implemented in the OpenFOAM CFD toolbox [3]. The thermal coupling was implemented by means of the Boussinesq hypothesis. Previous analyses showed the need of improvement of FCI thickness and thermal properties in order to obtain a desirable liquid metal temperature gain of 300 °C. In the present study, an assessment through sensitivity and parametric analyses of the required FCI thickness is performed.Numerical simulations have been carried out considering a Robin-type thermal boundary condition which assumes 1D steady state thermal balance across the solid FCI and Eurofer layers. Such boundary condition has been validated with a fluid–solid coupled domain analysis.Results for the studied flow conditions and channel dimensions show that, in order to obtain a liquid metal temperature gain of about 300 °C, the required FCI material should have a very small effective heat transfer coefficient ((k/δ) ≤ 1 W/m²K) and fluid velocities should be about 0.2 m/s or less. Moreover, special attention has to be placed on the temperature difference across the FCI layer. However, for a maximised liquid metal thermal gain, higher velocities would be preferable, what would also imply a reduced temperature difference across the FCI layer.     

基于互连线插值的时间数字转换器结构设计

全数字锁相环(All-digital Phase Locked Loop,ADPLL)中时间数字转换器(Time-to-Digital Converter,TDC)用于测量数控振荡器(Digitally Controlled Oscillator,DCO)输出时钟和参考时钟之间分数相位差,其分辨率越高,环路的相位噪声特性越好。为了提升TDC的测量分辨率,提出了一种对工艺偏差不敏感的环形互连线插值的TDC结构。本文首先给出了基于互连线插值TDC的系统结构,然后提出了一种工艺偏差不敏感的互连线结构实现等延时方法,并给出了环形的版图布局方案,最后利用仿真对提出的等延时实现方法进行验证。实验结果表明:该方法即使是在0.18μm CMOS工艺下也能将TDC的分辨率提高至皮秒级。