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.

Based on the VAR model and 30 annual sample data from 1991 to 2020, the main factors affecting the fluctuation of operating events are studied from four aspects: operational events, the number of nuclear power units, the proportion of nuclear power relative to the total power generation in China, and nuclear power generation. The results show that four factors are Granger causes of running events. The fluctuation of running events is the most affected by itself and has a sticky effect on itself. The fourth stage still has a 61

本文介绍了中国、国际原子能机构和美国的法规及标准对核电厂调试试验项目的相关要求,结合功能和物项的分析并考虑国内成熟的工程经验,确定了华龙一号试验项目选取流程.对试验程序进行分类得到11条选取原则,并将其与《核电厂调试程序》(HAD 103/02)附录Ⅰ进行对比,得出结论:选取的试验项目满足导则要求.同时,通过分析13个新概念和新设计的特性,明确了其验证方式.以上方法确定的调试试验程序,其完整性和充分性满足核安全要求,能够确保核电厂安全完成调试工作,达到核电厂的设计目的.

国内某核电厂1号机组发生了操纵员错误关闭1RRI公用负荷隔离阀导致乏燃料水池失去冷却的运行事件,本文运用故障树分析法对该事件原因进行分析.通过梳理事件序列,确定事件过程中的主要失效点,作为故障树最上层的顶事件,从顶事件出发,不断查找故障树上一层失效的原因,找出导致主要失效点的深层次原因.最终确定事件发生的根本原因是:操纵员试验准备、工作技能不足,且操作过程中未采取自检或其他防人因失误的方法;机组长屏障失效,未对操纵员提供有效的监护和支持;核电厂对重大高风险活动的准备和管控不足.最后提出针对性的改进建议.

The MELCOR program was used to simulate the severe accidents in the hot section of the primary circuit system of the large advanced passive pressurized water reactor,and the release behavior of the fission products of the late failure in the containment was explored and performed sensitivity analysis.The results show that when the containment is ruptured,94.51% of the inert gas is quickly released from the breach into the environment.The CsI that originally accumulated in the primary circuit is gasified again under the action of residual heat,and the share of the inert gas into the containment and the environment is only 5.02% and 1.45%.The size of the break in the hot section has a greater influence on the release share of fission products in the primary circuit and the environment,and the area of the break in the containment is not sensitive to the calculation results.

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.

2012-2021年,国内运行核电厂共发生17起辐射监测系统相关运行事件,其中70.6％的事件会导致辐射监测丧失冗余,存在放射性监测不及时风险.因此,这类事件的分析和研究对于各运行核电厂非常重要.导致辐射监测系统相关运行事件的主要原因是人因失误、设备硬件故障、信号冗余逻辑缺乏,以及管理失效.根据事件的主要原因,提出有针对性的改进建议,避免类似事件重复发生,为运行机组降低辐射监测系统相关运行事件发生频率提供了经验反馈和参考.

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.

研究核安全级管道地震分析的模态组合方法,对比几种模态组合方法的差别.首先采用PIPESTRESS软件建立某核安全2级管道模型,通过地震反应谱分析方法,应用不同的模态组合方法(平方和平方根法(SRSS)、分组法、10％法、二次组合法、完全二次组合法(CQC法))进行力学计算;其次通过ANSYS软件建立相同管道模型并进行时程计算,与PIPESTRESS不同的模态组合结果进行对比分析.结果表明,应用反应谱分析方法计算地震应力时,地震应力因模态组合方式的不同而差异较大.各种模态组合方法中,以CQC法计算得到的应力比值最小,而且该方法也与时程分析结果更接近.应用反应谱分析方法计算地震应力结果都比时程分析结果大,各种模态组合方式能满足正确性和保守性要求.

对压水反应堆分别采用反应堆平衡循环寿期末和燃耗包络两种计算方法计算堆芯积存量,对比结果的差异.结果表明:各种核素受计算方法的影响程度不同,83mKr、135Xe和138Cs等10余个核素受影响较大,燃耗包络法计算结果更为保守,其余核素受影响较小.核素放射性活度随着反应堆运行时间的增长可分为核素活度逐渐增加、核素活度先增大后趋于稳定、核素活度逐渐减小和核素活度先增大后减小等不同的变化规律.

A large number of radioactive fission products are released into the environment and cause harm to the human directly in the case of severe accidents.In this paper,the MELCOR program was used to study the existence form of CsI in the primary coolant system and containment,as well as the migration and release behavior of CsI and inert gas to the containment and environment.The results showed that CsI was mainly released in the form of aerosol.Most of the CsI retaining in the primary coolant system was deposited on the heat structures.About 70% of the CsI migrated into the containment in the form of aerosols and continuously deposited in the containment or dissolved in the water,a small amount of CsI released to the environment.Most of the inert gas migrated into the containment after the accident and only a small portion remained in other reactor systems.Only 0.11% of inert gas released to the environment under normal containment leakage rate.

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.

With the continuous improvement of NPP digital I&C system and network, much attention needs to be paid to the threats faced by NPP information security system.This paper aims to address some of the issues in this regard.It starts with an introduction of potential risks in the current control system with the case of Stuxnet attacks.Followed by the hidden hazards existed in the NPP information security system are discussed.Then a demonstration of practices adopted by US NRC when confronting security menace in NPP information security system is introduced.Finally,it proposes several recommendations on nuclear safety supervision based on the characteristics of China’s NPP.

The function of the service power system of a nuclear power plant is to provide safe and reliable power supply for the nuclear power plant facilities.The safety of nuclear power plant power supply is essential for nuclear safety.The serious accident of Fukushima Daiichi nuclear power plant occurred due to loss of service power and the ultimate heat sink.The service power system has two independent offsite power supplies as working power and auxiliary power.This article collected events of loss of offsite power supply in operating nuclear power plants at home and abroad,and analyzed the plant status and cause of loss of offsite power supply events,and proposed improvement measures for dealing with loss of offsite power supply.