As a conservative strategy to deal with instrument and control signal failure, logic degradation design has been often used in the safety instrument and control (I&C) system of nuclear power plants. For example, in the typical safety I&C system (TXS system) of a pressurized water reactor nuclear power plant, logic degradation is added as a degradation strategy when the I&C signal fails. However, it is found that the logic degradation will be triggered by mistake in the operating unit, resulting in the shutdown of the unit, which increases the safety risk. In this paper, the design of logic degradation is analyzed and the defects in the initial design is explained, and optimization and improvement is carried out targeting the found problems, so that the false triggering of logic degradation of the safety-level I&C system can be avoided when the normal functions are still in operation, so as to improve the operation stability and safety.

针对核电厂机组能力因子分类研究缺少相对简单有效的方法,基于第一至第八次《中华人民共和国核安全公约国家报告》中世界核电营运者协会(WANO)性能指标的数据,提出一种随机森林模型(random forest,RF)的机组能力因子分类方法,通过估算随机森林模型决策树的棵树、内部节点再划分所需要的最小样本数等,构建最优的随机森林分类模型,成功实现对能力因子的快速和精细分类,为第九次国家报告中定性掌握我国核电机组发电状况及行业内机组所处状况提供依据;同时,选用解决二分类的Logistic回归作对比试验,试验结果表明RF分类算法的总体精度达到77.27％,Kappa系数为0.705 3,达到高度一致性检验标准区间,明显高于Logistic回归的51.14％和0.1101,RF表现出分类效果好、准确率高和性能稳定等优点,能够有效提高机组能力因子分类的准确度.

2009-2019 年我国运行研究堆发生 50 起外电源失电导致停堆事件,降低了研究堆的安全性和经济性,因此,研究和分析此类事件对于各运行研究堆是非常重要的.本文通过对此类事件进行统计和原因分析,确定事件发生的主要原因.根据此类事件的主要原因,通过优化运行计划、加强人员培训、完善协作机制、加强设备监测和维护、加强施工管理、完善预防异物管理等应对措施来降低此类事件的发生频率.本文为研究堆降低外电源失电导致停堆事件的发生频率提供了经验反馈和参考.

BackgroundTime series usually have the characteristics of linear and nonlinear. Single model has certain limitations, which proposes mixed models for time series prediction.PurposeThis study aims to explore the application of the combination of Mann-Kendall test, differential autoregressive mobile average model (ARIMA) and long and short-term memory (LSTM) used in the prediction of the number of operational events of nuclear power plants (NPP) collected in Nuclear Safety of China and Annual Report of Nuclear Safety.MethodsFirstly, the R software was used to build ARIMA (2,1,2) model to obtain the linear part of operation events with the number of nuclear power plant operation events from 1991 to 2018, and LSTM model was developed to predict the deviation sequences, hence the nonlinear part of the number of operation events was derived from those deviation sequences. Then, combined model of ARIMA and LSTM was established to predict the number of operational events. Finally, the predicted values based on measured data were verified by actual measured data.ResultsThe verification results show that the ARIMA and LSTM combination model can be employed to improve the prediction accuracy effectively by 3%, and the predicted values of operation events in nuclear power plants from 2019 to 2020 are similar to the data collected in Annual Report of Nuclear Safety.ConclusionsThe combined model can better fit the time series of the number of operating events of NPP and correct the error of the single model.

本文通过对突发公共事件与核事故两者相通性和不同特点的探讨,概述了我国核事故应急法规体系与组织体系现状,并透过此次新冠疫情应急与防控过程中暴露的薄弱环节,借鉴疫情防控工作中的经验教训和成功举措,基于我国核事故应急管理工作实际情况,提出对核事故应急管理的相关建议,希望对我国未来的核事故应急管理工作提供参考.

1991年1月至2019年12月期间我国运行核电机组共发生23起误碰运行事件,其绝对数量不多,但其引起的后果较严重(60.9％造成紧急停堆),降低核电厂的安全性和经济性.误碰运行事件具有偶然性和随机性,其发生时间与反应堆投入运行时间的长短没有必然联系,因此,误碰运行事件的经验反馈对于各运行核电厂都是非常重要的.从事电气检修、脚手架搭设或拆除活动是发生误碰较多的时期,占比分别为39.1％和21.7％.误碰运行事件的根本原因可以归为6大类:操作人员原因,组织管理原因,设计原因,规程原因,培训原因,设备安装原因.根据误碰运行事件根本原因,可通过应用防人因失误工具、完善作业流程和作业现场管理、改进系统设施的设计、完善规程编制、优化员工培训、加强经验反馈工作的实效性等防范措施来减少误碰运行事件的发生频率.本文为运行机组降低误碰运行事件发生频率提供了经验反馈和参考.

核电厂运行事件一直是监管当局关注的重点,核电厂运行事件的上报可为监管当局了解不断发生的事件、监测机组性能、确认执照基准、识别更多重要事件的先兆、研究潜在的共性安全问题、评价运行经验的趋势、向电厂反馈经验提供保障.本文介绍了我国核电厂运行事件报告制度修订的背景,结合最新核电厂运行事件报告制度对核电厂运行事件报告准则进行解读,并应用准则对典型案例进行分析.

近年来我国M310系列核电厂在运行和试验期间多次发生一回路压力超出技术规范要求的事件.相关事件主要发生在机组余热排出系统冷却正常停堆模式(NS/RRA模式)和功率运行模式(RP模式)oNS/RRA模式下操纵员对一回路系统干预操作较多,由于操纵员技能不熟练、风险分析不到位、参数监控缺失、高风险操作监护不到位等因素导致操纵失误是NS/RRA模式下一回路压力超出技术规范要求的主要原因.RP模式下,M310系列核电厂运行技术规范对一回路压力的要求范围较小且没有规定超压后的干预措施,导致定期试验、设备故障或运行瞬态引发机组负荷快速变化时,稳压器压力控制系统来不及响应,频繁发生一回路压力超出技术规范要求的事件.基于上述事件分析结论,通过加强NS/RRA模式下操纵员行为管理,改进M310系列核电厂运行技术规范要求,能够有效避免一回路压力超出运行技术规范要求.

某AP1000型核电厂在主给水丧失手动停堆后S信号自动触发,在恢复机组状态期间操纵员人因失误多次导致安全系统动作,并出现了堆芯出口过冷度低于0 ℃℃的情况.本文运用事件原因因素图(ECF)和因果分析法对该事件进行了根本原因分析.通过梳理事件序列,确定了事件发展过程中的失效点,通过对各失效点的深入分析,得出事件的根本原因为营运单位对工作计划或过程的有效性监督不够和应急运行规程不完善,并提出针对性的改进建议.

我国已投运的核电厂陆续发生海洋异物入侵导致取水系统堵塞的运行事件,对机组的运行产生了较大影响,甚至可能会威胁核电厂的最终热阱安全.本文选取某一典型的取水口堵塞事件,利用屏障分析法列出所有能够防止事件发生的物理屏障和管理屏障,并对相关屏障失效进行分析,从而找出事件发生的根本原因,为后续预防此类事件提出指导建议.

核电厂冷源相关系统的功能丧失能够威胁机组安全.针对近期国内核电厂出现海洋异物堵塞取水口事件或异常,本文首先简单介绍了国内核电厂典型取水系统设计;然后对国内海洋异物堵塞影响核电厂冷源事件进行梳理,分析了国、 内外典型冷源堵塞事件;最后总结了以往核电厂预防和应对此类情况时存在的问题,并针对问题给出经验反馈建议,以期提高核电厂应对冷源堵塞突发情况的能力.

本文介绍了美国提出FLEX策略的背景,总结了FLEX策略的内容和特点,并结合国家核安全局发布的《福岛核事故后核电厂改进行动通用技术要求》提出了几点建议.

Nuclear reactor pressure vessel ( RPV) is one of the critical equipments for a nuclear power plant ,and its integrity will impact the safe operation of the nuclear power plant .To ensure the integrity of the reactor pressure vessel ,safety concern is highlighted in design ,manufacture ,installation and operation phase .It provided a reference for the nuclear power plant reactor pressure vessel in design ,manufacture , installation,operation and maintenance phase by introducing the material development of reactor pressure vessel ,typical degradation model of reactor pressure vessel ,and analyzing reasons for the degradation and proposing relevant measures to ensure the integrity of RPV .

Degradation of tube of steam generator will affect the integrity of primary loop ,after analysis the degradation model of tube ,and introduction of nondestructive testing technology application for in -serv-ice tube and steam generator tube life estimates ,take the corresponding protective measures per the cause of degradation of the tube ,to ensure safe operation of the tube of the steam .