秦山第二核电厂乏燃料水池失去冷却后最短响应时间分析

全厂断电事故工况下,反应堆乏燃料水池冷却和处理系统存在较大的停运风险。为避免反应堆乏燃料水池失去冷却事故工况的进一步恶化,使用ORIGEN-S程序计算了不同状态下从乏燃料水池失去冷却到乏燃料组件裸露的最短时间。结果表明,在最恶劣工况下,乏燃料组件裸露的最短时间为79.2h,该结果也被用于制定秦山第二核电厂的应急响应行动计划。     

严重事故情况下环形燃料堆芯氢气产量分析

秦山Ⅱ期核电站反应堆堆芯采用环形燃料后,锆装量将增加约88%,在严重事故情况下,堆芯氢气产量的变化是一值得关注的问题。利用MELCOR程序模拟环形燃料堆芯,建立典型严重事故序列分析模型,分析结果表明:在堆芯熔化过程中,与传统棒状燃料堆芯相比,环形燃料堆芯氢气产量没有明显增加,使用环形燃料还能推迟事故进程,缓解事故后果。核电站采用环形燃料,不会增大氢气燃烧的风险。     

液态金属反应堆湿式燃料贮存桶内部事件概率安全分析

液态金属冷却剂在给反应堆带来运行安全与热效率优势的同时,也给反应堆带来了复杂的换料系统,其中大型液态金属反应堆采用的湿式乏燃料贮存桶是乏燃料卸料过程的核心设备,临时装载了大量的乏燃料组件,具备一定的安全风险。本文采用概率安全分析（PSA）方法对乏燃料贮存桶进行风险评价,通过运行状态分析、始发事件分析、事故序列分析以及简单的定量化,初步获得其导致乏燃料组件发生损伤的事故序列和最小割集,识别了关键系统与设备。结果表明,相对于反应堆本身的风险,乏燃料贮存桶本身风险虽低但依然不可忽略,且风险评价结果对反应堆的运行方式以及清洗系统的可靠性较为敏感。此外还对该系统的设计改进与安全优化进行了讨论。     

FHR在全厂断电事故下对RVACS散热能力的要求

氟盐冷却高温堆(Fluoride salt-cooled High-temperature Reactor,FHR)是一种采用包覆颗粒燃料、高温熔融氟盐冷却剂的先进反应堆。部分FHR概念采用了反应堆容器辅助冷却系统(Reactor Vessel Auxiliary Cooling System,RVACS)导出事故下的堆芯余热。RVACS通过导热、对流换热、辐射换热等非能动过程,在事故发生时将堆芯余热排出至大气中。本文采用中国科学院上海应用物理研究所设计的10 MW FHR作为基准,利用RELAP5-MS程序,对其在全厂断电事故下的瞬态过程进行了模拟,验证了RVACS的余热导出能力。本文进一步研究了高反应堆功率情况下的全厂断电事故的瞬态过程,探讨了不同反应堆功率的FHR对RVACS散热能力的要求。     

高温气冷堆新燃料运输货包的撞击事故分析

介绍了高温气冷堆新燃料运输货包严重撞击事故的仿真计算分析方法。根据实际货包结构及运输条件,确定了分析的严重撞击事故景象。通过有限元法计算分析了货包在不同姿态、不同速度下的碰撞结果,给出了容器不同部分及所装载的燃料组件的损坏情况。在此基础上,计算了严重事故景象下有效增殖因子k_eff。     

小型堆包壳破损状态下利用稳压器去除放射性研究

利用MELCOR程序对小型船用堆稳压器喷雾除气过程及停堆过程进行建模,进而模拟核动力装置从功率运行至降功率除气,以及除气结束后停堆消除稳压器气腔的全部物理过程。通过对反应堆关键运行参数变化趋势的仿真分析,验证了模拟的物理过程的合理性。结合建立的除气及停堆仿真模型,计算分析了包壳破损状态下,稳压器喷雾除气、停堆过程对稳压器内惰性气体含量的影响,评估了稳压器高点放气和喷雾除气对放射性物质的去除作用。研究结果能为小型堆包壳破损状态下放射性安全管理策略提供指导和帮助。     

MELCOR乏燃料水池严重事故计算分析

针对长时间全厂断电（SBO）事故,采用MELCOR程序建立了乏燃料水池的计算分析模型,研究了乏燃料组件加热升温、锆包壳氧化等严重事故现象,并计算了向乏燃料水池注水缓解严重事故的效果。研究表明：乏燃料水池内的严重事故进程相对缓慢,且与乏燃料水池初始水位直接相关;向乏燃料水池注水是缓解乏燃料水池严重事故的有效手段之一。     

AP1000乏燃料池非能动冷却系统事故后冷却能力分析

AP1000乏燃料池冷却系统采用了先进的非能动设计理念,事故后以池水升温-沸腾的方式带走衰变热,并通过持续的非能动安全补水保证乏燃料安全。对AP1000乏燃料池冷却系统的事故后冷却能力进行分析发现,在核电厂正常换料工况和应急整堆芯卸载工况下,安全水源重力注水能保证事故后72 h内乏燃料安全;在核电厂正常整堆芯换料过程中应等待约56 h,以保证非能动安全壳冷却水箱可为乏燃料池补水,确保堆芯和乏燃料池安全。长期补水可以通过预留的安全接口持续进行。补水手段事故后有效,仅需操纵员有限干预。相对传统乏燃料池冷却系统设计,AP1000能更好地应对冷却丧失的事件。     

Safety evaluation on the depressurization accident in the gas turbine high temperature reactor (GTHTR300)

Japan Atomic Energy Agency has been developing a gas turbine high temperature reactor (GTHTR300) with electric power of approximately 300 MW. One of the unique safety design concepts of this system is that events with frequency of occurrence of higher than 10⁻⁸/reactor-year are evaluated as design basis events in order to show that the frequency of large amount of FP release is less than 10⁻⁸/reactor-year. According to this concept, a depressurization accident by a large break of helium piping is postulated as a design basis event. This accident is one of the most serious accidents in the high-temperature gas-cooled reactors from the viewpoint of loss of coolability. The safety evaluation on the accident was conducted based on the actual design of the system. The short-term and long-term behaviors of fuel temperature after occurrence of the accident, internal pressure of the reactor building, oxidation behavior of fuels and graphite structures were evaluated and exposure dose of general public was also estimated using the results of evaluation of fuel temperature and fuel failure by oxidation. All of the evaluation results meet the safety criteria and feasibility of the GTHTR300 was shown by this study.     

Intrinsic Safety of Future BN-800 Based Nuclear Technology

More than 40 years of experience in performing research and development work and operation of fast sodium-cooled reactors is analyzed. It is shown that such reactors possess a system of intrinsic safety properties, making possible long-time reliable operation and reducing to a minimum the consequences of an accident.A BN-800 unit under construction with the core switched to nitride fuel can serve as a basis for nuclear technology with intrinsic safety in accordance with the requirements of the strategy for the development of nuclear power in Russia in the first half of the 21st century.     

HTR-PM两根一回路连接管断裂的进气事故分析

进气事故是模块式高温气冷堆关注的超设计基准事故之一,石墨氧化腐蚀反应可能导致反射层结构强度减弱、燃料元件完整性和包容裂变产物能力被破坏,以及产生可燃气体等较严重后果。进气事故的分析研究对进一步掌握高温气冷堆的事故特性以及提高反应堆的安全设计具有重要意义。本文基于200MWe球床模块式高温气冷堆示范工程（HTR-PM）的初步设计,假设与一回路压力边界上、下相连的燃料元件进料管和卸料管同时发生断裂,从而形成烟囱效应并导致空气进入堆芯,利用高温气冷堆专用系统分析软件TINTE对自然循环建立及后续的进气腐蚀过程进行了研究,分析了自然循环流量、堆内石墨腐蚀速率、舱室氧气消耗量、燃料元件温度等关键参数的变化。结果表明,即使考虑腐蚀反应的不均匀性,事故后约60h时才会出现首个燃料包覆颗粒裸露现象,燃料元件最高温度峰值低于1620℃的设计限值,保持完好的燃料包覆颗粒仍具有包容放射性裂变产物的能力。同时,如果在相应的时间内采取措施切断进气源,使石墨腐蚀反应不能继续发展,将不会对反应堆的安全造成严重的影响。     

Analysis of fuel pin behavior under slow-ramp type transient overpower condition by using the fuel performance evaluation code ‘FEMAXI-FBR’

FEMAXI-FBR has been developed as the one module of the core disruptive accident analysis code ‘ASTERIA-FBR’ in order to evaluate the mixed oxide (MOX) fuel performance under steady, transient and accident conditions of fast reactors consistently. On the basis of light water reactor (LWR) fuel performance evaluation code ‘FEMAXI-6’, FEMAXI-FBR develops specific models for the fast reactor fuel performance, such as restructuring, material migration during steady state and transient, melting cavity formation and pressure during accident, so that it can evaluate the fuel failure during accident. The analysis of test pin with slow transient over power test of CABRI-2 program was conducted from steady to transient. The test pin was pre-irradiated and tested under transient overpower with several % P ₀/s (P ₀: steady state power) of the power rate. Analysis results of the gas release ratio, pin failure time, and fuel melt radius were compared to measured values. The analysis results of the steady and transient performances were also compared with the measured values. The compared performances are gas release ratio, fuel restructuring for steady state and linear power and melt radius at failure during transient. This analysis result reproduces the measured value. It was concluded that FEMAXI-FBR is effective to evaluate fast reactor fuel performances from steady state to accident conditions.     

核电站非能动辅助给水系统仿真研究

以先进核电站AP1000为研究对象,在其蒸汽发生器二次侧设计了1套耗汽驱动汽动辅助给水泵的非能动辅助给水系统。使用RELAP5程序计算分析全厂断电事故下设计系统的运行特性,研究其应对事故工况的能力。计算结果表明：全厂断电事故下,设计的非能动辅助给水系统可有效地排出堆芯余热,保证反应堆的安全;由于冷却剂体积收缩,170 min时稳压器排空;该系统可连续运行200 min,排出事故后的大部分堆芯余热。非能动辅助给水系统可作为全厂断电事故后的应急缓解方案。     

大亚湾核电站延伸运行技术的研究与实施

延伸运行(SO)是指当一回路的硼浓度接近0mg/L时,通过降温和降功率引入反应性,以保证反应堆加深燃耗继续保持功率运行,世界上许多核电厂采用SO.大亚湾核电站成功实施了我国的首次延伸运行.延伸运行作为一个特定的运行模式,需要进行相关的设计论证和安全分析.由于连续或阶跃式的降负荷和降温度,核测量系统和反应堆控制保护系统的参数需要进行特殊设置.按照发电计划的安排,大亚湾核电站的第一次延伸运行于2003年3月11日到3月20日实施,顺利实现了错开大亚湾核电站209大修和100大修的目的.     

Design of the primary containment for pool and loop arrangements of LMFBRs

LMFBR prototypes use different technical concepts for the primary system: France and the UK are constructing pool-type reactors, the US and DEBENELUX have selected loop-type reactors. Obviously, the relationship between the technical concept and the possibilities of limiting the consequences of a hypothetical whole-core accident is a widely discussed question. Three modes of loading phenomena are considered: (1) the transient pressures due to expansion of a vaporized fuel; (2) the transient pressures given by a coherent sodium-fuel interaction; and (3) the ‘equilibrium’ pressure given by transferring the excess heat in the fuel to an amount of sodium which produces the highest possible quasi steady-state pressure in the system. The structural response of the pool and loop systems are studied with respect to salient modes (2) and (3).Axial forces during the accident have to be transferred via the plug and core support to the reactor vessel support. The technical solutions depend on the primary system concept. The given structures can be supplemented by special devices to protect the cover and the vessel against excessive loads. To a first approximation, such safeguards are independent of the technical concept. Post-accident heat removal is accomplished for commercial plants preferably by in-vessel solutions. The expenditure for in-vessel solutions depends more on the singularities of a given design than on the particular design concept. The intermediate (primary/secondary sodium) heat exchanger is a critical component of the containment system. The coupling between the source of the accident and the intermediate heat exchanger is different in both systems. Pool and loop systems are both adequate in limiting the consequences of an unprevented nuclear excursion of a reasonable size. Advantages and disadvantages are well-balanced for both systems.     

49-2游泳池式反应堆超设计基准事故的筛选与分析

为保证49-2游泳池式反应堆在超寿期下的安全运行,需进行超设计基准事故分析。由于难以采用概率安全评价(PSA)方法进行分析,所以本文无条件假设最严重事故来得到一保守结果。主要分析了全厂断电下未能紧急停堆的预期瞬变(ATWS)、水平孔道断裂和停堆后堆芯完全裸露的事故,以及应急能力。结果表明:在全厂断电ATWS下堆芯是安全的;水平孔道断裂及其他因素造成失水时,只要2.5h内堆芯不裸露即可保证燃料元件不熔化;非能动破坏虹吸能力和多样的应急补水方式能保证堆芯不裸露。     

Integrated MELPROG/TRAC analyses of a PWR station blackout

A complete, coupled, mechanistic analysis of the entire reactor coolant system during a station blackout accident (TMLB') has been completed using the MELPROG/TRAC code. The analysis includes the failure of the seal on all coolant pumps at 100 min into the accident; in all other respects the case is identical to a previous station blackout calculation. Both cases started at accident initiation and continued through boiloff of the water, failure of the control and fuel rods, oxidation of the zircaloy and the formation of U---Zr---O eutectics, failure of the vessel internal structures due to melting and loading, massive core disruption, and subsequent vessel failure. The two cases reached significantly different end conditions. The basic TMLB' resulted in a high pressure (15 MPa) vessel failure approximately 4 h after accident initiation. The addition of a 12.5-mm hole in each pump seal caused the water in the loop seal to clear and resulted in a significantly lower pressure (0.27 MPa) at vessel failure, which occurred almost 10 h after accident initiation. Therefore, high pressure melt ejection (HPME) and the potential for subsequent direct containment heating (DCH) were predicted not to occur in the TMLB' accident scenario with pump seal failure.     

HTR-PM进气事故缓解措施初步分析

热气导管双端断裂(DEGB)事故因其可能造成的严重后果逐渐引起研究者的大量关注。对于200 MWe球床模块式高温气冷堆(HTR-PM),DEGB进气事故是其事故安全分析中重点关注的事故类型。针对HTR-PM DEGB进气事故,提出了从装料管注入一定流量的氮气或氦气以缓解事故后果的方案,并利用系统分析程序TINTE-TIIXUW,计算分析了注入不同流量氮气和氦气对进气事故的缓解效果。分析结果表明,注入氮气时,注气流量需达到一定值才能起到缓解效果,而注入氦气时,注气流量小或大均能有效缓解事故后果,这为后续的实际工程应用提供了很好的参考和帮助。     

Analyses with the FSTATE code; fuel performance in destructive in-pile experiments

Thermal-mechanical analysis of a fuel pin is an essential part of the evaluation of fuel behavior during hypothetical accident transients. The FSTATE code has been developed to provide this required computational ability in situations lacking azimuthal symmetry about the fuel-pin axis by performing 2-dimensional thermal, mechanical, and fission gas release and redistribution computations for a wide range of possible transient conditions. In this paper recent code developments are described and applications is made to in-pile experiments undertaken to study fast reactor fuel under accident conditions. Three accident simulations, including a fast and slow ramp-rate overpower as well as a loss of cooling accident sequence, are used as representative examples, and the interpretation of FSTATE computations relative to experimental observations is made.     

HTR-10燃料元件的气体输送

为了保证高温气冷实验堆球形燃料元件可靠地输送，采用了传递管输送方法，本文介绍了10MW高温气冷堆（HTR－10）燃料元件气体输送系统的关键设备，管路设计及输送气体流量计算，通过初装料的运行，证明该系统运行良好。