基于密度锁的非能动余热排出系统特性分析

以基于密度锁的非能动余热排出系统为背景,通过实验对该系统正常运行时密度锁的封闭特性及事故工况下密度锁的开启特性进行了分析验证。用RELAP5/MOD3.2程序对发生事故时非能动余热排出回路瞬态运行特性进行了仿真,并与实验值进行比较,二者均符合较好。结果表明,正常工况下,密度锁能有效隔离主回路和余热排出回路,余热排出回路处于非工作状态;事故发生时,在较大的重力蓄能作用下,非能动余热排出系统能够瞬间投入工作,并逐渐建立稳定的自然循环以载出余热。     

基于密度锁的非能动余热排出系统设计及验证分析

提出了一种新型非能动余热排出系统设计方案,该方案以密度锁技术作为基础,采用改变压力调节回路流量,并保持循环回路内有高温工质流动的方式,建立密度锁内水力平衡关系,维持主回路和余热排出回路的隔离。以AP1000主冷却剂系统为载体,用RELAP5/MOD32程序分析了正常工况下,非能动余热排出系统的运行特性。结果表明：以密度锁内流体温度作为控制变量对调压泵转速进行调节,可逐渐建立密度锁内水力平衡关系,实现非能动余热排出系统的启动;稳态运行期间,反应堆运行参数改变时,在控制系统反馈作用下,密度锁仍能维持“封闭”状态,保证主回路和余热排出回路隔离。     

密度锁内分层界面的作用分析

进行了冷态和热态实验,结合理论分析研究了密度锁的抗扰动机理。冷态时,流体流动产生的压力差引起了密度锁中各通道流体的大环流运动;热态时,密度锁内分层界面的形成对大环流运动起到了阻碍作用。结果表明:由于压力差作用,密度锁内分层界面向一侧倾斜产生重位差;当压力差与重位差相平衡时,大环流运动被阻止,流体达到分层平衡。     

密度锁栅格结构对分层稳定特性影响

对密度锁内流场进行理论分析和实验观察,研究了栅格结构对密度锁分层稳定特性的影响.结果表明:在无分层时,密度锁内为涡旋流动;有分层时,涡旋被限制在分层上方,涡旋与分层相互作用,直至达到平衡;无栅格时,密度锁存在多个平衡点,分层容易从一个平衡点过渡到下个平衡点,很难稳定;有栅格时,分层能较快地达到平衡点,且由于栅格增强了能...     

密度锁启动特性实验研究及计算验证

以基于密度锁的非能动余热排出系统（PRHRS）为研究背景,实验验证了密度锁自平衡启动方案的可行性。结果表明：主回路流量接近平衡流量启动PRHRS时,密度锁内冷热流体温度分界面将在不平衡力作用下向上或向下移动,减小或增大了余热排出回路重位压差,使密度锁内冷热流体温度分界面在新的位置达到受力平衡,最终实现密度锁的自平衡启动,以及余热排出回路与主回路的隔离。依据一维连续性方程、能量方程及动量方程建立数学模型,用Matlab语言编程,对密度锁启动过程进行了数值模拟分析,证明了密度锁自平衡启动方案合理、有效。计算值与实验值符合较好,用该程序可较好地模拟密度锁自平衡启动过程中系统的瞬态运行特性。     

密度锁自平衡启动特性的实验研究

以应用密度锁的非能动余热排出系统为背景,结合实验研究和理论分析,对密度锁自平衡启动的运行特性及可行性进行研究。结果表明：自平衡启动可分为关阀预热和开阀平衡两个阶段,在这两个阶段内能分别实现密度锁“关闭”所必需满足的两个条件,达到隔离非能动余热排出回路与主回路的目的。在关阀预热阶段,密度锁借助其特殊结构,有效地控制了传热方式转变点的位置,促进了热/冷流体交界面的形成;在开阀平衡阶段,借助其水力平衡的自稳定特性,有效地控制了热/冷流体交界面的移动,建立了密度锁内的水力平衡。所得结果充分证明了自平衡启动方法的可行性。     

密度锁内水力平衡特性分析和实验研究

通过简化的理论模型,分析得出在反应堆正常运行工况下,密度锁处于"关闭"状态时必须满足的水力平衡条件,并对影响该条件的主要参数进行分析.结果表明:密度锁内的水力平衡在一定范围内具有自稳定的特性.同时,建立模拟实验同路,对该特性进行实验验证,针对稳态运行过程中主回路内工质流量改变的工况进行实验研究.实验结果表明:当运行参数的变化打破水力平衡后,依靠自稳定特性,能够很快恢复密度锁内的水力平衡,而不会影响密度锁的封闭性和反应堆的正常运行.     

密度锁内分层传热特性的初步探讨

通过可视化观察方法,对3种不同实验管内的流体分层传热特性进行实验研究,同时,建立传热计算模型,对密度锁内的传热机理进行分析.结果表明:密度锁内的分层工质自上而下分为:混合层、界面层、导热层.混合层内的传热以对流为主,其余两部分的传热以导热为主.对不同管径的研究表明,密度锁内的蜂窝通道能有效地抑制扰动作用,减小混合层的厚度,降低通过密度锁的热量传递.     

密度锁内稳态分层特性的实验研究

通过可视化观察方法,对3种不同实验管内的冷热流体分层特性进行实验研究,同时,根据界面力的平衡条件,对密度锁内分层的稳定性进行了分析。稳态工况下,密度锁内冷热流体间存在一界面层,且界面层内具有较大的温度梯度;界面层的稳定性受温度交界面处的扰动速度及界面层内温度梯度的影响,稳定的界面层对阻止冷热流体搅混具有积极作用。另外,对实验管内有无隔板情况进行分层特性对比实验,表明密度锁内的蜂窝通道不但有利于界面层的稳定,且有利于界面形成位置的控制。     

密度锁启动过程中传热特性的实验研究

分别在无扰动以及扰动大小不同的实验情况下,对密度锁启动过程中的传热特性进行了实验研究.研究结果表明,密度锁能抑制热量下传.根据传热情况,密度锁内过渡区可分为强分层、弱分层和无分层3种情况.强分层和弱分层情况下,密度锁都能有效地阻止热量下传,且强分层向下传热量更小.而在无分层情况下热量连续不断地从密度锁传出,导致密度锁失效.     

ATWS Characteristics of Super LWR with/without Alternative Action

Anticipated-transient-without-scram (ATWS) of the supercritical-pressure light water cooled thermal reactor with downward-flow water rods (Super LWR) is analyzed to clarify its safety characteristics. At loss-of-flow, heat-up of the fuel cladding is mitigated by the water rods removing heat from the fuel channels by heat conduction and supplying their coolant inventory to the fuel channels by volume expansion. The average coolant density is not sensitive to the pressure due to the small density difference between “steam” and “water” at supercritical-pressure. Closure of the coolant outlet of the once-through system causes flow stagnation that suppresses an increase in the coolant density due to an increase in the temperature. Therefore, the increase in power is small for pressurization events. The coolant density and Doppler feedbacks provide good self-controllability of the power against loss-of-flow and reactivity insertion. An alternative action is not needed either to satisfy the safety criteria or to achieve a high-temperature stable condition for all ATWS events. Initiating the automatic depressurization system is a good alternative action that induces a strong core coolant flow and inserts a negative reactivity. It provides an additional safety margin for the ATWS events. Even the high core power rating of the Super LWR has excellent ATWS characteristics, providing a key reactor design advantage.     

混合能谱超临界水冷堆快谱区流动稳定性研究

在混合能谱超临界水冷堆中,冷却剂通过堆芯过程中跨拟临界点引起的密度等参数的剧烈变化易导致系统产生密度波振荡而不稳定,因此混合能谱超临界水冷堆的稳定性对系统的安全性至关重要。本文利用频域法研究快谱区的流动稳定性,给出在不同状态下的稳定性边界,同时对冷却剂入口流量、进出口压差和通道划分等对稳定性的影响进行了分析。结果表明：大的入口流量有利于系统的稳定;高的进出口压差对系统稳定性有利;轴向功率均匀分布较非均匀分布系统的稳定性差,可提供保守结果;热通道的功率密度越大,对系统的稳定越不利。研究结果对超临界水冷堆设计和优化有一定指导价值。     

Development of an Advanced Startup Procedure for a PIUS-type Reactor

An advanced startup procedure for the PIUS-type reactor has been developed. The procedure is related to the way to isolate the primary loops from the borated reactor pool by establishing stable hot/cold water interfaces in the so-called density lock sections. The procedure starts with accumulating preheated water in the high points of the steam-generator-side legs. Then, by restarting the reactor coolant pumps, the primary loops can be isolated from the pool as the primary loops reaches a uniformly higher temperature than the pool water. The additional components required for this procedure are only a low-pressure grade heater and a pump of small capacities. Since the isolation is achieved with the density locks left open, the core shutdown and cooling capabilities by means of the natural circulation of borated water are maintained in case of any abnormal events during startup. The feasibility and the predictability of this procedure were investigated by running an experiment in a scaled single-loop facility and conducting an analysis using a one-dimensional model. Both in the experiment and in the analysis. the primary loop was successfully isolated from the pool.     

绕丝结构对氦氙气体流动换热特性影响研究

在开放栅格式气冷空间堆堆芯的设计中,会在燃料棒上采用绕丝结构,这将对工质的流动换热特性产生很大影响。本文采用CFD方法开展了He-Xe混合气体在气冷空间堆典型带绕丝燃料通道内的流动换热特性的数值研究,获得进出口温度、压力、流速及流体密度等参数的空间分布。结果表明引入绕丝使得范宁摩擦因子出现大幅增加,部分绕丝结构会使努塞尔数降低20%～30%,且本文所研究5种绕丝结构热工水力性能比均小于1。研究结果对于气冷空间堆堆芯热设计、提高系统的安全性具有重要意义。     

Effects of ship motions on natural circulation of deep sea research reactor DRX

DRX is a very small integral type PWR (750 kW_t) for a scientific deep-sea research bathyscaph. The core having a small amount of steam is cooled by natural circulation and pressurized by self-pressurization. During operation of the bathyscaph in a deep sea or near the water surface, a ship inclination or ship motions will affect the reactor behavior. This paper describes the effect of a heeling or a heaving on the thermal hydraulic behavior of reactor system, which is analyzed by improved so to simulate the effect of ship motions. The dynamics has a feature of nuclear power-natural circulation flow coupling under the condition of external forces. The analysis shows that ship inclination induces the core flow to decrease but reactor power recovers to the initial level without help of the reactor automatic control system. The heaving makes the core flow and the reactor power oscillate in phase with heaving, which are different from a density wave oscillation. Oscillation amplitudes of the flow and the power have peaks at the heaving period of 5 s. The peaks are due to resonance of the natural circulation flow and the heaving. An effective measure to suppress this oscillations due to heaving is to pressurize the primary loop by filling non-condensable gas. The density wave oscillation occurs when the reactor power increases over the rated power, and the boundary of its occurrence is analytically revealed. Under the condition of both density wave oscillation and heaving, the system shows to oscillate with the overlapped effect.     

Flow Simulation and Optimization of Plasma Reactors for Coal Gasification

This paper reports a 3-d numerical simulation system to analyze the complicated flow in plasma reactors for coal gasification, which involve complex chemical reaction, two-phase flow and plasma effect. On the basis of analytic results, the distribution of the density, tempera-ture and components‘ concentration are obtained and a different plasma reactor configuration is proposed to optimize the flow parameters. The numerical simulation results show an improved conversion ratio of the coal gasification. Different kinds of chemical reaction models are used to simulate the complex flow inside the reactor. It can be concluded that the numerical simulation system can be very useful for the design and optimization of the plasma reactor.     

非对称条件下铅冷双环路自然循环系统抗扰动能力分析

自然循环铅冷快堆热交换器服役在高温、高压差、高密度和高腐蚀的恶劣环境下,易诱发传热管破裂和堵流事故,导致反应堆非对称热负荷或非对称阻力运行,对反应堆的安全稳定运行具有重要影响。本文以铅冷双环路自然循环系统为研究对象,采用无量纲分析方法,推导双环路系统自然循环流量理论解;分别开展不同负荷差或阻力差下自然循环系统扰动特性分析,采用拟合逼近的方法建立表征自然循环抗扰动能力的特征参数,并获得最佳抗扰动区间。研究结果表明,当系统引入一定的热负荷扰动和阻力扰动后,环路流量变化不大,此时系统抗扰动能力较强。      

旁流对一回路非能动余热排出系统运行特性影响分析

非能动余热排出（PRHR）系统是反应堆安全运行的重要保障,但现有研究表明,一回路系统存在旁流现象,其提高了堆芯活性区流量,在增强堆芯换热的同时也增加了系统的流动阻力,使系统运行情况更加复杂,因此,需对旁流的影响进行建模分析。本文基于一维N-S方程,建立了考虑旁流的PRHR系统运行特性分析模型;在对模型进行验证的基础上,揭示了旁流存在的机理,分析了其对PRHR系统运行特性的影响规律。研究结果表明,旁流的存在降低了PRHR系统的排热能力,影响了反应堆的非能动安全性,在反应堆余热排出系统设计和安全分析过程中需考虑旁流的影响。     

反应堆冷却剂系统流量测量试验研究与设计

华龙一号（HPR1000）设置了反应堆冷却剂泵进出口压差表用于测量反应堆冷却剂系统（RCS系统）环路流量,取消了二代改进型核电机组设置的弯管流量计。环路流量测量方式的改变直接影响RCS系统流量测量试验的实施。通过研究主泵的运行特性和系统的阻力特性,提出了基于主泵电功率测量RCS系统流量的试验方法。结合理论分析结果和工程实践经验,给出了反应堆冷却剂惰走流量试验的试验方法和验收准则。研究表明,主泵电功率法可以测量RCS系统的流量,反应堆冷却剂惰走流量可以通过主泵惰转过程的转速变化进行验证。      

Experimental investigation of natural circulation instability in a BWR-type small modular reactor

The Purdue NMR (Novel Modular Reactor) represents a BWR-type small modular reactor with a significantly reduced reactor pressure vessel (RPV). Specifically, the NMR is one third the height and area of a conventional BWR RPV with an electrical output of 50 MWe. Experiments are performed in a well-scaled test facility to investigate the thermal hydraulic flow instabilities during the startup transients for the NMR. The scaling analysis for the design of natural circulation test facility uses a three-level scaling methodology. Scaling criteria are derived from non-dimensional field and constitutive equations. Important thermal hydraulic parameters, e.g. system pressure, inlet coolant flow velocity and local void fraction, are analyzed for slow and fast normal startup transients. Flashing instability and density wave oscillation are the main flow instabilities observed when system pressure is below 0.5 MPa. And the flashing instability and density wave oscillation show different type of oscillations in void fraction profile. Finally, the pressurized startup procedure is recommended and tested in current research to effectively eliminate the flow instabilities during the NMR startup transients.