核电站循环水系统瞬态计算和虹吸破坏阀选型分析

以Flowmaster软件作为计算工具建立了核电厂循环水系统模型,计算了停泵工况下虹吸破坏阀故障不打开时循环水系统的最大水锤压力,对虹吸破坏阀的通流口径选取和阀门打开时间进行了敏感性分析,给出了能有效消除水锤的虹吸破坏阀选型要求。     

热工水力系统程序中数值水锤问题研究

基于两流体六方程的热工水力系统程序在计算蒸汽即将从控制体中消失或水即将充满控制体工况时,由于空泡份额较小的两相混合物和纯液相之间可压缩性的不连续变化以及离散动量方程的离散方法,可能会出现虚拟的压力峰值,即数值水锤现象。本文以热工水力系统分析程序RELAP5为参考对数值水锤问题的缓解方案进行了分析研究,给出了详细的检测逻辑以及修正方案,并应用于普赖尔管问题和冷凝实验工况的计算分析。结果显示,数值水锤缓解方案的启用能够缓解两流体程序中针对该类问题由于数值方法带来的压力瞬态效应,从而能够明显地降低压力峰值,避免了严重扭曲瞬态解的出现。数值水锤缓解方案减缓这一虚拟压力峰值,有利于提高程序计算的稳定性;针对该问题此方法可为同类型系统程序的开发及模型优化提供参考。      

压水堆核电厂主给水管道水锤计算及分析

核电厂二回路主给水系统是保证蒸汽发生器冷却的重要系统,同时也是水锤频发的管段,研究水锤对主给水系统的规律对于系统稳定运行具有重要意义。文章以主给水系统作为研究对象,通过Flowmaster软件的瞬态计算功能,建立给水泵、控制阀门等边界条件下的数学模型,计算阀门、泵关闭时产生的水锤压力,并且导出压力等参数的瞬时变化解。结论验证了Flowmaster瞬态计算功能计算水锤的可行性,结合工程实例说明,增加给水控制阀、给水泵关闭时间能有效控制水锤,改变给水泵、给水控制阀关闭触发信号间隔能缓解水力冲击,以及管径等因素对水锤的影响,对于实际工程中的设计和系统优化具有一定指导作用。     

基于耦合程序的流体瞬变流动水锤现象分析

水锤现象严重威胁系统的安全,而设备的启闭是产生水锤现象的重要因素之一。本文针对并联双泵系统建立耦合程序,计算研究泵启动和阀门关闭时的流体瞬变水锤现象。验证过程证明了耦合程序的正确性,并将三维稳态模型计算结果与实验结果进行了对比,二者符合良好。瞬态分析中,动网格技术成功模拟阀门关闭,并获得了闭合时阀内的重要热工水力参数。通过对比泵启动耦合计算结果与传统RELAP5计算结果可知,耦合程序能正确预测水锤压力波和水锤载荷。耦合分析较一维计算能更直观地展现系统中重要设备内的流体瞬变特性。计算获得的三维瞬态特性能对阀门的设计和优化提供重要的参考。     

900 MW压水堆一回路系统水锤特性研究

针对压水堆水力过渡过程,建立了三环路900 MW压水堆一回路系统水锤完整的数理模型及边界条件。采用特征线法,开发了FORTRAN水锤仿真程序,并对三泵并联在启动和切换工况下的水锤特性进行了数值研究。研究发现启动和切换过程中,发生2次流量突变、流向逆转、压差突变和振荡;流量突变和逆转均发生在阀门关闭支路,呈振荡衰减的波动趋势,最大倒流流量达1 370 m3/h;压差突变发生在后启动支路,压差振荡最大值达40kPa;并联泵启动方式决定倒流流量和压差突变大小。     

旋启式止回阀关阀水锤优化分析

建立了双泵并联给水系统数学物理模型,针对旋启式止回阀关闭过程中形成的水锤进行编程计算,分析作用在止回阀阀板上的力矩以及阻尼扭簧力矩对关阀水锤的影响。结果表明：在双泵并联给水系统中,旋启式止回阀在关闭时会产生明显水锤,作用在阀板上的力矩对水锤的作用效果有一定影响,选择合适的止回阀阀板材料以及加装合适的弹簧可有效缓解水锤危害。     

CEFR二回路水锤分析

CEFR以液态钠作为一、二回路冷却剂。二回路蒸汽发生器泄漏发生钠水反应会在二回路系统中引起水锤,水锤事故可以引起管道的甩摆,拉断管道支撑,使管道破裂,甚至直接造成核电厂事故停堆。因此,水锤是CEFR设计和安全分析中的一个重要问题。本工作在清华大学按照CEFR一、二回路系统初步设计参数编制的水锤分析程序的基础上,采用CEFR二回路冷却系统施工设计参数重新进行分析计算。CEFR二回路水锤分析@唐龙 @王彬     

考虑流-固耦合效应的空间管道水锤方法研究

介绍耦合水锤理论的4方程模型和其求解方式,以及利用计算流体力学(CFD)计算流-固耦合的方法,并采用文献作为算例进行水锤流-固耦合的计算。通过CFD的经典水锤计算,为流-固耦合计算选定计算格式和网格,同时与文献进行比较。结果表明,本文所用的方法可用于较复杂的管道水锤的流-固耦合计算。     

某核电机组一回路升温期间安注管道异响事件分析

本文针对某核电机组在一回路冷态水压试验升温过程中,非能动堆芯冷却系统安注管道发生异响事件进行了深入的研究分析,利用伯努利方程和达西公式对模型进行流体计算,结合系统布置、设备结构等特点,发现4 台主泵以50%转速运行的工况下,会在堆芯补水箱内部建立起反向流,造成系统内压力脉动,从而引起水锤产生异响.表明通过主泵运转对堆芯...     

核岛重要厂用水系统停泵水锤计算分析

核岛重要厂用水（SEC）系统是核岛向最终热阱（大海）的直流海水输热系统、安全级系统,必须长期稳定、安全、可靠的运行。文章通过数值模拟的方法计算SEC系统停泵时的水锤过程,分析空气阀、单向调压水箱、缓闭止回阀水锤防护方案在SEC系统中的适用性。     

Numerical simulation and optimization on valve-induced water hammer characteristics for parallel pump feedwater system

In this study, the method of characteristic line (MOC) was adopted to evaluate the valve-induced water hammer phenomena in a parallel pumps feedwater system (PPFS) during the alternate startup process of parallel pumps. Based on closed physical and mathematical equations supplied with reasonable boundary conditions, a code was developed to compute the transient phenomena including the pressure wave vibration, local flow velocity and slamming of the check valve disc, etc. Some interesting results were obtained and it was shown that severe slamming between the valve disc and valve seat occurred during the alternate startup of parallel pumps. The induced maximum pressure vibration amplitude is up to 5.0 MPa, which occurs under the high–high speed startup condition. The scheme of appending a damping torque with the check valve disc was also numerically performed to eliminate the water hammer for the optimum design purpose. The adoption of damping torque slows down the closing speed of the check valve and has been approved to be an effective approach. This work is expected to be instructive for the optimum design of the PPFS in NPPs so as to mitigate the potential damage caused by valve-induced water hammer.     

核动力系统冗余泵组的可靠性研究

根据核动力系统中设备冷却泵的工作状态,将冗余泵组的中止回阀看成两个冗余阀,得出简化的可靠性分析框图,并建立泵组的可靠性分析模型.以核动力装置设备冷却泵组为例,分别计算泵组在3种情况下的可靠度.计算结果表明,冗余泵组比单个泵工作的可靠性高,但冗余泵组中泵和阀之间的相关失效削弱了泵组的可靠性.     

Mitigating check valve slamming and subsequentwater hammer events for PPFS using MOC

The method of characteristic (MOC) was adopted to analyze the check valve-induced water hammer behaviors for a Parallel Pumps Feedwater System (PPFS) during the alternate startup process. The motion of check valve disc was simulated using inertial valve model. Transient parameters including the pressure oscillation, local flow velocity and slamming of the check valve disc etc. have been obtained. The results showed that severe slamming between the valve disc and valve seat occurred during the alternate startup of parallel pumps. The induced maximum pressure vibration amplitude is up to 5.0 MPa. The scheme of appending a damping torque to slow down the check valve closing speed was also performed to mitigate of water hammer. It has been numerically approved to be an effective approach.     

Dynamic simulation of accidental closure of intermediate heat exchanger isolation valve in a pool type LMFBR

In a pool type liquid metal cooled fast breeder reactor (LMFBR), core and other internals such as pumps, heat exchangers are immersed in a pool of sodium. Heat exchange from primary sodium circuit (pool) to secondary sodium circuit (loop) is through four intermediate heat exchangers (IHX) immersed in primary sodium pool. Each IHX is provided with a sleeve valve at its primary sodium inlet window for the purpose of isolating the shell side of IHX from the sodium pool. With such a provision, an inadvertent partial or complete closure of a sleeve valve of one of the IHX during normal operation of the reactor has been considered as a design basis event for the reactor. One dimensional transient thermal hydraulic models of the primary and secondary sodium circuits have been developed to study the thermal hydraulic consequences of such an event. The main areas of concern in the plant and the availability of safety parameters for the detection of the event have been evaluated.     

Fluid dynamic interaction between water hammer and centrifugal pumps

Centrifugal pumps generate in piping systems noticeable pressure pulsations. In this paper the dynamic interaction between water hammer and pressure pulsations is presented. The experimental investigations were performed at a piping system with nominal diameter DN 100 (respectively NPS 4) and 75 m total length, built at the Institute for Process Technology and Machinery. Different measurements at this testing facility show that pulsating centrifugal pumps can damp pressure surges generated by fast valve closing. It is also shown that 1-dimensional fluid codes can be used to calculate this phenomenon. Furthermore it is presented that pressure surges pass centrifugal pumps almost unhindered, because they are hydraulic open.     

Operating experience with an on-line vibration control system for PWR main coolant pumps

The main circulation pumps are key components of nuclear power plants with pressurized water reactors (PWRs), because the availability of the main circulation pumps has a direct influence on the availability and electrical output of the entire plant. The on-line automatic vibration control system ASMAS was developed for early failure detection during the normal operation of the main circulation pumps in order to avoid unexpected outages and to establish the possibility of preventive maintenance of the pumps. This system is permanently and successfully operating in three German 1300 MW_el NPP's with PWR and has been successfully tested in a 350 MW_el NPP with a PWR.     

并联立式屏蔽电机主泵流动特性数值研究

以缩比系数为1∶4的立式屏蔽电机反应堆主冷却剂循环泵（简称主泵）为研究对象，建立2台并联主泵反向旋转（模型1）和同向旋转（模型2）2种几何模型；运用计算流体力学（CFD）方法对2种模型的并联主泵内部流场进行稳态运行计算，从主泵的外特性、进口流动特性、入流品质、管内压力分布方面对模型1和模型2进行对比分析。结果表明，模型1中A、B主泵性能基本一致；模型2中A、B主泵的流量相对偏差基本在0.8%以内，最大值达到1.69%，扬程相对偏差稳定在1%以内，效率和轴功率相对偏差最大值分别达到6%和8%；模型2相对模型1流动稳定性更好、入流品质更高、管内压力分布较低，有利于设备的长期运行。