压水堆燃料元件包壳破损在线监测系统研制

针对压水堆核电厂运行工况下燃料元件包壳发生破损的情况,通过以机理性定量分析方法为基础的诊断物理模型和在线监测系统设计,给出完整的包壳破损在线监测解决方案。同时,通过理论模拟计算、原理样机带源实验以及电厂实测运行数据验证,多方面验证了系统设计的正确性。该套系统能够改进中国改进型百万千瓦级压水堆(CPR1000)机组现有燃料破损监测手段的不足,提高压水核电机组运行的安全性能。     

智能化核电厂燃料包壳破损在线监测装置研制

研制一套智能化核电厂燃料包壳破损在线监测装置,采用高纯锗反康谱顿散射探测系统在线测量一回路冷却水特征放射性核素的活度,采用多核素组耦合的分析方法实现燃料包壳破损的在线诊断。通过检定校准试验,实测⁵⁷Co、¹³⁷Cs和⁶⁰Co的相对标准偏差的绝对值小于3%;20 mL样品的可探测活度最小可达到6.5 Bq。     

智能化核电厂燃料包壳破损在线监测装置研制

An intelligent on-line monitoring device for fuel cladding defect has been developed. HPGe with anti-Compton scattering detection system is used to measure the activity of characteristic radionuclides in primary cooling water, and the multi-nuclide group coupled analysis method is used to diagnose the defect of the fuel cladding. The verification and calibration test shows that the absolute relative standard deviations of the measured typical nuclides 57Co, 137 Cs and 60Co are less than 3%, and the minimum detectable activity can reach 6.5 Bq.     

水堆燃料元件的破损监测、定位和处理

本文简介反应堆破损燃料元件的监测、定位和处理；反应堆运行时的监测与定位；换料时或换料后的监测；在燃料组件内鉴别破损的燃料棒；破损燃料棒拆出后的监测与定位；燃料组件的监测、拆卸和修复等方面在国际上的研究开发现状。     

基于~(137)Cs、~(85)Kr的燃料元件包壳破损检测系统研制

针对停堆时间在4个月以上、不具备脱水条件而又不能采用常规方法检测其包壳是否破损的燃料元件,研制一种检测系统,利用高温水加热燃料元件使放射性核素向外释放,施加压力加速放射性核素释放,通过收集并检测137Cs和85Kr含量来确定燃料元件是否破损。应用结果表明,系统可以在不脱水状态下完成燃料元件包壳的破损检测,具有检测方便、快捷、准确的特点。     

压水堆核电厂燃料包壳破损诊断方法研究和改进

分析了国内外压水堆核电厂燃料包壳破损诊断方法以及存在的问题，从燃料棒破损数量、破损尺寸和燃耗3个方面对压水堆核电厂燃料包壳破损的诊断方法进行了改进，并对可能影响诊断结果的因素进行了探讨。应用我国在役核电厂实际的运行数据对诊断方法进行了验证，结果表明，改进后的燃料包壳破损诊断方法可准确地诊断燃料包壳破损情况，且有更广泛的适用性。      

研究堆燃料元件铝合金包壳表面温度限值研究

为了提高中子注量率水平,在建或在研的先进高通量研究试验堆需要更高的功率密度和热流密度,使得研究堆燃料元件铝合金包壳的使用温度不断提高,已接近其运行限值。本文对正常运行工况(工况1)和预计运行事件(工况2)下铝合金包壳表面温度限值及其确定方法进行研究。分析认为,对于研究堆用铝合金包壳,在工况1下包壳表面温度的主要限制因素是包壳材料的机械性能和保证冷却剂不沸腾;在工况2下按设计总则要求应保证燃料包壳不破损,具体应限制燃料芯体最高温度和包壳应力,不需要直接对包壳表面温度提出限值,但包壳表面温度与前2者仍存在关联性,应给予关注。     

水冷动力堆燃料元件包壳的水侧腐蚀

从反应堆运行工况及材料因素,讨论了水堆燃料元件包壳的水侧腐蚀问题。为满足高性能燃料元件的要求,包壳的水侧腐蚀性能需要改善。本文根据最近的一些研究结果,讨论了各种可能有效的措施。     

法国压水堆燃料元件新一代包壳材料的发展

概述了法国对核电站燃料元件包壳材料锆合金的开发与研究现状,着重介绍了所开发的新锆合金（Ｍ２,Ｍ３,Ｍ４,Ｍ５合金）在堆内外的性能。其中Ｍ４和Ｍ５合金包过央燃料棒燃耗达到５５ＧＷ．ｄ．ｔ＾－１的辐照考验结果表明,它们的堆内的腐蚀,蠕变和辐照伸长等性能优于改进型Ｚｒ－４合金包壳。     

基于人工神经网络的压水堆燃料破损状态监测

为提升对核反应堆燃料棒包壳破损的预测能力,建立两个串联的人工神经网络分别判断燃料棒包壳是否破损以及破损程度。通过改变沾污铀质量、增加数据扰动、改变运行功率和使用更少的特征核素进行训练,对用于判断是否破损的神经网络模型和判断破损等级的神经网络进行了性能测试和分析。在沾污铀质量小于0.5 g、数据扰动在30%以内、单棒功率在77 kW到120 kW之间的条件下,第1个人工神经网络能较好地判断出是否破损。第2个神经网络,对于考虑的5种破损程度,判断的精确性较高。与传统的碘同位素比值法相比,神经网络方法响应更快,精度更高。结果表明,人工神经网络可用于预测反应堆燃料包壳是否发生破损以及破损程度。     

水化学对燃料元件包壳腐蚀行为的影响

燃料元件包壳的水侧腐和吸氢是当前进一步提高燃耗的主要限制因素，由于一回路水中加入Ｈ３ＢＯ３和ＬｉＯＨ，使包壳的腐蚀问题变得更为复杂。本文综述了ＬｉＯＨ及ＬｉＯＨ－Ｈ３ＢＯ３对锆合金水侧腐蚀的影响，以及研究这种影响机理的现状。     

船用堆失水事故元件包壳破损温度阈值及气隙释放后果计算研究

针对船用堆特殊安全性要求,对船用堆失水事故包壳破损温度阈值进行研究。摒弃以往的保守假设,采用最佳估算模型,得到合理的温度阈值,并采用MELCOR程序对典型破口事故下包壳破损份额及气隙释放的放射性后果进行了计算。计算结果为评估舱室剂量、保障运行人员安全提供了依据。     

基于多物理场耦合的U3Si2燃料与双层SiC包壳组合的轻水堆燃料性能分析

基于COMSOL平台开发了一套基于多物理场全耦合的燃料性能分析程序,并通过径向功率分布模型对比验证了该程序的正确性与准确性;然后进一步分析了U₃Si₂燃料与双层SiC包壳组合、U₃Si₂燃料与锆合金包壳组合在反应堆正常运行工况下的性能,并与UO₂燃料与锆合金的组合进行了对比分析。计算结果发现U₃Si₂燃料与锆合金包壳组合相比UO₂燃料与锆合金的组合具有更低的燃料中心温度、裂变气体释放量及内压,但气隙闭合时间会提前;而U₃Si₂燃料与双层SiC包壳的组合相比U₃Si₂燃料与锆合金的组合具有更高的燃料中心温度、更大的裂变气体释放量及内压,且随着燃耗的增加,其燃料中心温度大幅增加,与锆合金包壳相比,双层SiC包壳能够有效延迟气隙闭合,缓解燃料与包壳的力学相互作用。      

RIA Failure Threshold and LOCA Limit at High Burn-up

A correlation for RIA fuel failure threshold has been derived and compared with recent experimental data. The correlation can be used for UO₂ and MOX fuel and at hot zero power and cold zero power transients, account taken for the different initial enthalpy and for the lower ductility at cold conditions. It can also be used for non-zero power transients, provided that a term accounting for the start-up power is incorporated. A probabilistic approach has been attempted for the cold zero power case. For LOCA, a correlation has been derived expressing the LOCA limit as a function of the hydrogen accumulated in the cladding during base irradiation. However, LOCA experimental data exhibit a significant scatter, possibly because results depend on details in the conduct of the tests. Consequently, predictions of LOCA limits vs. burn-up are affected by appreciable uncertainty, and more data derived from testing of high burn-up cladding specimens are needed in order to reach firm conclusions.     

An Analysis of Cladding Failure on Beam Transient of Lead-Bismuth-Cooled Accelerator-Driven System

The cladding failure analyses on various beam transients of Lead-Bismuth-cooled Accelerator-Driven System (ADS) were performed with ADSE code and the cladding failure analysis program. First, the cladding failure analysis program was developed. This program is intended for creep ruptures analysis using ADSE code and employs the method of Cumulative creep Damage Fraction (CDF) calculation. Beam diameter expansion, beam flattening, beam hollowing, and beam incident position change were analyzed for the ADS model proposed by JAEA. As a result, beam diameter expansion, beam flattening, and beam hollowing would not lead to cladding failures but beam incident position change was revealed to have a high risk for the cladding failures. Some core designs were proposed for the prevention of failure. The changes of sizes such as plenum length were not effective for CDF reductions. The application of SUS316FR steel cladding instead of Mod.9Cr-1Mo steel showed good performance but the application of SUS316FR steel needs some provisions for erosions and corrosions. The fuel composition change was very effective for CDF control and this measure would be the best modification for the prevention of cladding failures.     

Research Program to Elucidate Outside-in Failure of High Burnup Fuel Cladding

Among a series of power ramp tests on 25 Zr-lined segment rods of burnup ranging from 43 to 61 GWd/t, five segment rods failed during the power ramp tests. One segment rod irradiated for 3 cycles (43 GWd/t) failed with a pinhole due to PCI/SCC. The rest of higher burnups failed with an axial crack on the outer surface. The failure threshold power tended to decrease as burnup increases.

Post irradiation examinations revealed increased cladding hydrogen absorption and its precipitates in the cladding outer rim after 4 and 5 cycle irradiations, in contrast to a uniform hydride distribution and a small hydrogen content after 3 cycle irradiation. Metallographic observations suggested an axial crack failure mode induced by the combined effects of high stress and hydrides precipitated in a radial direction during power ramp.

The axial crack failure during the power ramp is supposed to be initiated by a cracking of radial hydride formed by hydride re-distribution and re-orientation at the cladding outer rim and to propagate through a process of hydride concentration and precipitation at the crack tip. Research programs of experimental and analytical studies to clarify the conditions of such mechanism are on-going focusing on the hydrogen behavior and mechanical performance of the irradiated cladding.     

安注方式对设计基准失水事故下元件包壳破损份额影响的分析

以某船用压水堆为研究对象,采用RELAP5/MOD32程序,分析了发生在主管道冷端的极限中破口失水事故中,采取冷端、热端安注方式时不同的事故过程。引入临界管概念,确定了包壳破损临界功率因子。对全堆进行精细功率重构,确定每根燃料元件功率因子,最终确定不同安注方式下的元件包壳破损份额,并指出：对破口出现在主管道冷段的设计基准事故,热端安注能减轻事故后果,减少破损份额。     

燃料棒包壳辐照蠕变与生长行为模拟研究

根据建立的包壳材料和行为模型,利用ABAQUS对包壳辐照蠕变与生长行为进行相关模拟研究。在设定的稳态工况下,计算了包壳的辐照蠕变,分析了它的应力以及蠕变的关系。通过设置节点集和不同路径方式,分析了包壳的辐照生长现象,表明了ABAQUS在核燃料性能研究方面的适用性。以及利用ABAQUS的二次开发接口,可以把自定义的模型结合到商用的有限元软件中,利用商用有限元软件的优势,快速解决部分核燃料模拟中的问题。