安全壳卸压排放过程模化分析

针对大型非能动先进压水堆安全壳卸压排放过程中涉及的重要热工现象,采用系统性的关键现象识别及重要性分析方法,得到了大型非能动先进压水堆卸压排放过程中的现象过程识别与排序表(PIRT)。结果表明:排放管线及鼓泡器中对安全壳卸压排放过程影响程度较高的现象为临界和摩擦流、两相压降、几何尺寸及流动状态;乏燃料水池中对安全壳卸压排放过程影响程度较高的现象为冷凝、传热、几何尺寸、流体混合、不凝性气体及热分层。利用关键现象识别及重要性分析结果与现有缩放实验台架的搭建经验及研究结果,得到了安全壳卸压排放过程验证性试验装置搭建中应该遵循的相似准则,从而为安全壳卸压排放验证性试验装置的搭建提供设计基础和理论依据。     

应用DAKOTA程序耦合WGOTHIC程序进行安全壳压力响应敏感性分析

安全壳压力响应分析是验证非能动安全壳冷却系统(PCS)设计的重要内容,需考虑PCS的传热传质等各种现象的影响。本文应用DAKOTA程序耦合WGOTHIC程序对大型先进压水堆非能动安全壳压力响应进行敏感性分析,通过偏相关系数,定量评价了重要现象识别和排序表(PIRT)中各种现象对安全壳压力的影响程度。研究结果表明:质能释放现象、安全壳内初始环境条件、冷凝/蒸发现象显著影响安全壳压力。该研究结果为安全壳设计、安全分析和安全审评提供技术支持。     

非能动安全壳冷却系统热工水力单项试验

非能动安全壳冷却系统热工水力单项试验研究是先进压水堆关键技术研究项目.本试验利用德国Karlsruhe研究中心的PASCO试验装置,并对其进行改造,主要研究事故工况下非能动安全壳环形空腔内传热传质机理,包括于平板传热试验、加热平板蒸发传热试验、辐射传热试验,从而获得不同温度、环腔尺寸、表面黑度、喷淋流量对流动及传热的影响,验证相关模型及为设计提供参考.     

AP1000安全壳流动循环与热分层一维模型分析

非能动安全壳冷却系统是先进大型压水堆AP1000核电厂的重要安全系统之一,该系统利用安全壳内及安全壳外空气流道中的自然循环过程将安全壳内的热量带至环境中,大空间内的循环与热分层现象对安全壳内的传热及流动特性具有重要影响。本文基于热分层理论,针对钢制安全壳内、外的自然循环过程,建立一维计算模型,在提高计算效率的基础上,得到安全壳内的温度分布,并与三维模型的计算结果进行了对比,验证了模型的合理性;同时得到了安全壳内压力及组分的分布。     

小破口失水事故非能动系统瞬态特性研究

为了解先进压水堆小破口失水事故下非能动安全壳冷却系统、非能动堆芯冷却系统、非能动余热排出系统的瞬态响应特性,需开展小破口失水事故下反应堆冷却剂系统和安全壳的耦合响应特性研究。分析结果表明,小破口失水事故下,耦合分析中非能动余热排出系统、非能动堆芯冷却系统、自动卸压系统和非能动安全壳冷却系统的特性与独立计算有较大差异,小破口失水事故下耦合分析得到的安全壳压力峰值小于独立计算。      

典型严重事故非能动安全壳冷却系统效果分析

先进压水堆采用非能动安全壳冷却系统(PCCS)在事故下维持安全壳完整性,包括重力喷洒形成安全壳外部水膜冷却和空气冷却流道中空气对流传热。针对严重事故下PCCS效果研究,建立了非能动压水堆安全壳及非能动安全壳冷却系统的传热分析模型(包括对流传热及蒸发/冷凝传热),并耦合反应堆主系统模型及专设安全设施模型。通过与西屋公司PCCS大尺度试验结果的比对验证了模型的可用性,进而针对非能动先进压水堆选取全厂断电、热段小破口失水始发事故作为典型严重事故序列,模拟了事故进程、主系统响应及安全壳的响应,分析了PCCS对安全壳的降温、降压作用。结果表明,安全壳压力72h内未超过安全限值,保持安全壳完整性。     

冷凝水收集装置对非能动安全壳热量导出系统影响试验研究

非能动安全壳热量导出系统（PCS）作为三代核电厂重要的安全系统,用于事故后安全壳的非能动冷却。利用大型安全壳综合试验装置,可开展安全壳内复杂的热工水力现象与安全系统之间耦合行为的研究。本文利用大型安全壳综合试验装置开展了PCS换热器冷凝水收集装置对PCS排热影响及收集率试验。结果表明,在工况范围内,换热器下方安装冷凝水收集装置对PCS的换热能力没有明显的不利影响,且其收集率较高。     

CAP1400核电站非能动安全壳冷却系统综合性能试验研究

CAP1400非能动安全壳冷却系统(Passive Containment Cooling System,PCS)仍采用与AP600和AP1000相同的先进非能动设计理念。本研究针对CAP1400的非能动安全壳冷却系统,设计并建造了非能动安全壳冷却系统综合性能试验平台(Containment safety vErification via integRal Test facility,CERT),开展了试验研究。对CAP1400非能动安全壳冷却系统综合性能试验验证需求,试验装置的设计特点、研究内容及代表性的试验结果进行了介绍。通过PCS综合性能试验的开展,研究了非能动安全壳冷却系统的事故响应特性及关键物理现象,为CAP1400的安全评审及相关安全分析程序验证提供了试验结果支撑。     

非能动堆芯应急冷却系统试验

为了研究先进压水堆非能动堆芯应急冷却系统中各主要设备的行为和系统性能.中国核动力研究设计院在AC-600全压堆芯补水箱补水性能实验装置的基础上建成了非能动堆芯应急冷却系统试验装置在该试验装置上,根据不同的冷端破口直径、不同的压力平衡管和不同的自动卸压系统操作逻辑进行了一系列试验试验结果表明,不同的试验条件下,非能动堆芯应急冷却系统能够对堆芯进行冷却     

非能动先进压水堆核电厂严重事故下裂变产物行为研究

非能动先进压水堆核电厂在严重事故下,安全壳可能发生失效,导致大量放射性物质向环境释放。本文针对非能动先进压水堆核电厂可能发生的早期失效、中期失效、晚期失效三种释放类别,建立百万千瓦级非能动先进压水堆的事故分析模型,分别针对自动卸压系统第二级卸压阀误开启,DVI管线上发生当量直径为4英寸的破口,以及热管段发生当量直径为2英寸的破口的典型严重事故序列,在研究事故进程的基础上,分析事故下裂变产物释放和迁移的特性,重点关注惰性气体、挥发性裂变产物和非挥发性裂变产物在核电厂的分布,最终计算释入环境的裂变产物源项。本文分析结果可为严重事故管理以及厂外放射性后果评价提供支持。     

Analysis on containment depressurization under severe accidents for a Chinese 1000 MWe NPP

Containment depressurization has been implemented for many nuclear power plants (NPPs) to mitigate the risk of containment overpressurization induced by steam and gases released in LOCA accidents or generated in molten core concrete interaction (MCCI) during severe accidents. Two accident sequences of large break loss of coolant accident (LB-LOCA) and station blackout (SBO) are selected to evaluate the effectiveness of the containment venting strategy for a Chinese 1000 MWe NPP, including the containment pressure behaviors, which are analyzed with the integral safety analyses code for the selected sequences. Different open/close pressures for the venting system are also investigated to evaluate CsI mass fraction released to the environment for different cases with filtered venting or without filtered venting. The analytical results show that when the containment sprays can't be initiated, the depressurization strategy by using the Containment Filtered Venting System (CFVS) can prevent the containment failure and reduce the amount of CsI released to the environment, and if CFVS is closed at higher pressure, the operation interval is smaller and the radioactive released to the environment is less, and if CFVS open pressure is increased, the radioactive released to the environment can be delayed. Considering the risk of high pressure core melt sequence, RCS depressurization makes the CFVS to be initiated 7 h earlier than the base case to initiate the containment venting due to more coolant flowing into the containment.     

基于威斯康辛冷凝试验本体的结构改进及分析

先进压水堆(APWR)是第三代核电技术的代表堆型之一,它采用了非能动安全系统,提高了安全性能。非能动安全壳冷却系统(PCCS)主要利用蒸汽的冷凝来带走安全壳内的热量。本文主要介绍了威斯康辛大学进行的冷凝试验的试验本体结构,应用ANSYS软件对其结构进行了应力分析,并在现有结构的基础上对外部加强筋布置进行了一定的改进和优化。通过计算和比较可以看出,经过改进后的加强筋布置,不仅满足原有的试验要求,结构布置合理,更提高了试验本体的承压能力,使其能够满足更高试验压力的需要。     

核电厂安全壳及其功能保障问题

根据国内外最新研究结果,综述了核电厂安全壳及其功能保障方面的主要问题,重点叙述了安全壳在严重事故下的行为、失效模式和导致安全壳失效的物理现象,讨论了安全壳功能保障中的排热减压、消氢、防止高压熔堆及防止底板熔穿等问题,最后简评了安全壳的改进措施。     

Modeling pressure suppression pool hydrodynamics in the ABWR containment

This paper focuses on the assessment of pressure suppression pool hydrodynamics in the advanced boiling water reactor (ABWR) containment under design-basis, loss-of-coolant accident (LOCA) conditions. The paper presents a mechanistic model for predicting various suppression pool hydrodynamics parameters. A phenomena identification and ranking table (PIRT) applicable to the ABWR containment pool hydrodynamics analysis is used as a basis for the development of the model. The highly ranked phenomena are represented by analytic equations or empirical correlations. The best estimate and several sensitivity calculations are performed for the ABWR containment using this model. Results of the sensitivity calculations are also presented that demonstrate the influence of key model parameters and assumptions on the pool hydrodynamics parameters. A comparison of model predictions to the results of the licensing analyses shows reasonable agreement. Comparison of the results of the proposed model to experimental data shows that the model predicted top vent clearance time, the pool swell height, and the bubble breakthrough elevation are within 10% of the data. The predicted pool surface velocity and the liquid slug thickness are within 30% of the measurements, which is considered adequate given the large uncertainties in the experimental measurements.     

超临界流体的泄压过程研究

超临界水堆(SCWR)的LOCA研究是安全分析的重点和难点,其中压力容器的喷放泄压过程的研究至关重要。本文通过对反应堆压力容器进行简化,建立了简单容器喷放的数学物理模型,开发了超临界流体的喷放瞬态计算程序。将该程序的计算结果与超临界二氧化碳的泄压喷放过程的实验数据进行了比较,计算值与实验结果吻合良好,验证了模型的正确性。运用该验证后的程序对超临界水的容器喷放过程进行了深入研究和分析,分析了不同初始条件、破口面积及加热功率等对泄压过程瞬态特性的影响。结果表明,本文建立的简单容器模型能模拟从超临界到亚临界压力的喷放泄压过程。计算结果可为超临界水堆的LOCA分析提供理论基础。     

Effect analysis of the intentional depressurization on fission product behavior during TMLB' severe accident

It has been found that the pressure in the reactor coolant system (RCS) remains high in some severe accident sequences at the time of reactor vessel failure, with the risk of causing direct containment heating (DCH).Intentional depressurization is an effective accident management strategy to prevent DCH or to mitigate its consequences. Fission product behavior is affected by intentional depressurization, especially for inert gas and volatile fission product. Because the pressurizer power-operated relief valves (PORVs) are latched open, fission product will transport into the containment directly. This may cause larger radiological consequences in containment before reactor vessel failure. Four cases are selected, including the TMLB' base case and the opening one, two and three pressurizer PORVs. The results show that inert gas transports into containment more quickly when opening one and two PORVs,but more slowly when opening three PORVs; more volatile fission product deposit in containment and less in reactor coolant system (RCS) for intentional depressurization cases. When opening one PORV, the phenomenon of revaporization is strong in the RCS.     

Influence of injection temperature and flow rate on mixing and stratification in small passively cooling enclosures

Thermal mixing and stratification phenomena may occur during the loss of a coolant accident or main steam line break accident in the containment of a Passive Containment Cooling System, or in the suppression pools in BWR. However, the present study pays insufficient attention to the thermal stratification phenomena in the containment of small modular reactors(SMR). In this paper, an investigation on the mixing and thermal stratification phenomena caused by the plumes or buoyant jets in SMR containments was carried out. The experiments were both conducted under non-adiabatic and adiabatic conditions for a steel containment. In each condition, two key parameters, inlet temperature, and flow rate were tested by controlling variables to identify their influence on the thermal stratification phenomenon. The visualization experiments illustrated the jet mixing and stratification development. The experiment results were compared with the numerical computation and they reached a good agreement.     

Detailed Evaluation of RCS Boundary Rupture during High-Pressure Severe Accident Sequences

A depressurization possibility of the reactor coolant system (RCS) before a reactor vessel rupture during a high-pressure severe accident sequence has been evaluated for the consideration of direct containment heating (DCH) and containment bypass. A total loss of feed water (TLOFW) and a station blackout (SBO) of the advanced power reactor 1400 (APR1400) has been evaluated from an initiating event to a creep rupture of the RCS boundary by using the SCDAP/RELAP5 computer code. In addition, intentional depressurization of the RCS using power-operated safety relief valves (POSRVs) has been evaluated. The SCDAPRELAP5 results have shown that the pressurizer surge line broke before the reactor vessel rupture failure, but a containment bypass did not occur because steam generator U tubes did not break. The intentional depressurization of the RCS using POSRV was effective for the DCH prevention at a reactor vessel rupture.     

Containment venting as a mitigation technique for BWR MARK I plant ATWS

Containment venting is studied as a mitigation strategy for preventing or delaying severe fuel damage following hypothetical BWR Anticipated Transient Without Scram (ATWS) accidents initiated by MSIV-closure, and compounded by failure of the Standby Liquid Control (SLC) system injection of sodium pentaborate solution and by the failure of manually initiated control rod insertion. The venting of primary containment after reaching 75 psia (0.52 MPa) is found to result in the release of the vented steam inside the reactor building, and to result in inadequate Net Positive Suction Head (NPSH) for any system pumping from the pressure suppression pool. CONTAIN code calculations show that personnel access to large portions of the reactor building would be lost soon after the initiation of venting and that the temperatures reached would be likely to result in independent equipment failures. It is concluded that containment venting would be more likely to cause or to hasten the onset of severe fuel damage than to prevent or to delay it.Two alternative strategies that do not require containment venting, but that could delay or prevent severe fuel damage, are analyzed. BWR-LTAS code results are presented for a successful mitigation strategy in which the reactor vessel is depressurized, and for one in which the reactor vessel remains at pressure. For both cases the operators are assumed to take action to intentionally restrict injected flow such that fuel in the upper part of the core would be steam cooled. Resulting fuel temperatures are estimated with an off-line calculation and found to be acceptable.