Study on Lightning Protection Design of DCS in a Nuclear Power Plant

DCS （distributed control system） plays a decisive role in the overall operation of a nuclear power plant. If DCS fails, it will seriously affect the normal production of nuclear power plant, causing great losses. So it is very important to take perfect lightning protection measures on DCS of the nuclear power plant. In this paper, according to the actual situation of DCS in a nuclear power plant, by controlling lightning point, securely booting lightning into the ground network, improving low-resistance ground network, eliminating ground loops, determining the safety space, surge protection of power and signal, a set of complete lightning protection design scheme was systematically put forward. Some specific lightning protection measures were highlighted, such as the DCS grounding, equipotential bonds and shields, and some specific considerations were put forward. All of these could offer reference in the practical application.

Radiation Exposure and Cancer Incidence (1990 to 2008) around Nuclear Power Plants in Ontario, Canada

Radiation doses and cancer incidence among the population living within 25 km of three nuclear power plants (NPPs) in Ontario, Canada were investigated for the period 1985 to 2008 for radiation exposure and 1990 to 2008 for cancer incidence. This study design provided at least a five-year latency period between potential radiation exposure and cancer incidence. Around the NPPs, the incidence of childhood cancers, leukemia and non-Hodgkin lymphoma, in young children (aged 0 - 4) was lower than the general Ontario population, but not statistically so. Cancer incidence in children aged 0 - 14 was similar to the Ontario population. Overall, for all ages there was no consistent pattern of cancer incidence (all cancers combined and radio-sensitive cancers) across the population living within 25 km of the three NPPs. Some types of cancers were statistically higher than expected, others were statistically lower than expected, and others were similar to the general Ontario population. Although variations in all cancers combined and radiosensitive cancers were found in this study, the pattern was found to be within the natural variation of cancer in Ontario. During the period 1985 to 2000 (Pickering and Bruce NPPs) and 1985 to 2002 (Darlington NPP) radiation doses to members of the public from the operation of the NPPs, estimated on the basis of a hypothetical individual at the facility fence line, were ≤0.052 mSv/year;while for the period 2001 to 2008 (Pickering and Bruce NPPs) and 2003 to 2008 (Darlington NPP) radiation doses, more realistically estimated using the critical group concept for six age classes, were ≤0.0067 mSv/year. Hence, public doses from environmental releases of radionuclides from Ontario NPPs represent a very small fraction of natural background radiation (1.338 and 2.02 mSv/year) in the regions where the NPPs are located. Our study shows no evidence of childhood leukemia clusters around the three NPPs and that the incidence of all the cancers investigated for all age groups is within the natural variation of the disease in Ontario. The radiation exposure from NPP operation is a small contributor to the public’s total exposure to radiation and is not a plausible explanation for any excess cancers observed within 25 km of any Ontario NPP.

Some Technical Solutions for Environmental Protection System during Accidents at Nuclear Power Plants

The paper reports some technical solutions, which suggested or used for increasing of environmental protection during accidents at NPPs. For NNPs with two protective shells and pressure release system such as WWER-1000 a comprehensive, passive-mode environmental protection system of decontamination of the radioactive steam-air mixture from the containment and the intercontainment area was suggested. This system includes the “wet” stage (scrubbers, etc.), the “dry” stage (sorption module), and also an ejector, which in a passive mode is capable of solving the multi-purpose task of decontamination of the air-steam mixture. For WWER-440/230 NPPs three protection levels: 1) a jet-vortex condenser;2) the spray system;3) a sorption module were suggested and installed. For modern designs of new generation NPPs, which do not provide for pressure release systems, a new passive filtering system together with the passive heat-removal system, which can be used during severe accidents in case all power supply units become unavailable, was proposed and after modernization was installed at the KudanKulam NPP (India).

Radiological monitoring results of the ambient environment around Qinshan Nuclear Power Plant

A plan of surveillance monitoring Qinshan Nuclear Power Plant (QNPP) has been implemented since 1992, the objective of which is to establish the database of environmental radiation information around QNPP, and to detect any unplanned discharge of radioactive materials from QNPP. This paper presents the monitoring results for radionuclide concentrations in the environmental matrices before and after QNPP operation. The radionuclide con- centrations in vegetation, food, atmosphere, soil and littoral soil samples have been determined. After operation of QNPP, the mean values of 137Cs, Sr and H in water are 0.6, 4.9 mBq/L and 1.7 Bq/L, respectively; the mean values 90 3 of137Cs in soil and littoral soil are 3.5 and 2.7 Bq/kg, respectively; the mean values of137Cs in rice, green cabbage, meat, mullet, milk and tea are 0.033, 0.039, 0.081, 0.069, 0.018 and 0.62 Bq/kg, respectively; the mean values of 90 Sr in rice, green cabbage and tea are 0.081, 0.315 and 4.1 Bq/kg, respectively; gross β activity in fallout is 0.9 Bq·m-2·d-1. Compared with the data before QNPP’s operation, no significant difference has heen observed in the radioactivity of137Cs, Sr, H and the gross β activity in ambient environmental matrices from 1992 to 2001, and 90 3 there are only some fluctuations within the range of background.

Radiation dose rate estimates to marine biota resulting from the routine radioactive releases of the nuclear power plants in Daya Bay

Five marine organisms in Daya Bay are selected for estimating the dose rates. Internal exposure and its 5 pathways are also considered. The concentrations of 43 kinds of background and additional radionuclides in seawater are from the survey of background radioactivity and the prediction of routine radioactive releases of the 4 reactors. Point source dose distribution functions are used to estimate the dose rates to various organisms from a and β radiation.

Violation of the Convention on the Protection of the Black Sea against Pollution,Bucharest’s Convention of 1992 and the Sofia Protocol of 2018 by Turkish Government’s Sinop Nuclear Power Complex Project

On September 12th,2020,the Turkish Ministry of Environment and Urban Planning issued a final approved version of an EIA(Environmental Impact Assessment)report for the Sinop(4,800 MWe)nuclear power plant and nuclear fuel fabrication complex project,located on Turkey’s Southern Black Sea coastline,in the Sinop Providence,which will be built on a BOO(Build-Own-Operate)basis by an offshore company known as General Directorate of Electricity Generation Inc.(EUAS)International ICC,along with unknown shadowy partners and investors.This project violates the Convention on the Protection of the Black Sea against Pollution,namely,Bucharest’s Convention of 1992,and the Sofia Protocol of 2018 which are established to preserve the uniqueness of the Black Sea,sustain the fisheries,and protect marine life.The Black Sea is the largest anoxic water basin in the world with oxygen rich surface waters supporting marine life which constitute only about 13% of the Black Sea volume.For the rest of the entire Black Sea at a depth greater than 150-200 m,there is a permanent hydrogen sulphide zone devoid of life,the oxygen is completely absent after this level.This unique bio-hydrological characteristic has been regulating the preconditions of its following distinctive biodiversity for thousands of years.The biologically rich regions are only limited to only oxygen rich shelf zones,with depths of up to 50-100 m in the southern coast line,and in the northern Black Sea shallow-water areas with depths of up to 5-10 m.This water body,bordering the hydrogen sulphide zone,is approximately 200-300 m wide and averages 5-50 m deep,in which high concentrations of fish eggs and larvae strive,and circulate counterclockwise along 4340 km coastline of the Black Sea.

控制棒对核动力航天器辐射屏蔽特性的影响

针对控制棒及其导向管贯穿阴影式屏蔽体的情况,本文进行了核动力航天器全场辐射屏蔽特性的分析,并提出局部屏蔽的优化方案。利用蒙特卡罗方法在核动力航天器全场范围内对中子与光子进行输运计算,求解得到控制棒吸收体处于不同位置时的中子注量率与光子剂量分布情况,分析了控制棒及其导向管对阴影屏蔽体的屏蔽特性及航天器全场辐射特性的影响,并针对辐射薄弱点提出了局部屏蔽优化方案,对优化后的方案进行了计算验证。结果表明:控制棒导向管垂直贯穿屏蔽体会导致仪器平台辐射剂量超限值,极端工况下光子剂量达到限值的10倍,中子注量达到了限值的1.8倍。利用局部屏蔽体可以有效消除控制棒导向管带来的辐射剂量超限问题,能在控制质量增幅的情况下保证仪器平台所处区域的辐射安全。

核电厂安全级DCS缺省值设置策略研究

针对数字化仪控系统中无效信号的质量位随意蔓延使系统处于一种不确定状态的问题,结合核电厂运行工况和信号特性,对龙鳞平台故障诊断机制和信号质量位标识进行研究。考虑故障安全准则,系统性地提出缺省值设置原则。从信号执行功能和信号边界两个维度进行分析,确认缺省值的设置范围,并详细给出执行保护功能、报警功能、维护和试验功能信号的缺省值设置策略。同时,针对传统的缺省值验证方式无法全面、有效地进行缺省值验证的问题,提出一种利用全范围模拟机和虚拟数字化控制系统(DCS)进行缺省值验证的新方法。利用该方法可有效地对DCS内设置的缺省值进行系统性的验证。所提出的缺省值设置策略和验证方法可为后续核电厂安全级DCS的缺省值分析和设置提供全面的指导。

IEC 63096核电厂仪控系统网络安全管控标准与国内等级保护相关标准的协调分析

伴随着全球工业数字化、网络化和智能化的发展,传统基于物理隔离的保护方式已无法确保核电厂仪控系统的网络安全。核电厂仪控系统遭受网络攻击不仅可能导致生产过程中断,还可能引起核安全事件,因此核电厂仪控系统网络安全已引起世界各国及相关国际组织的高度关注。国际电工委员会于2020年发布了关于核电厂仪控系统网络安全防范管控的国际标准IEC 63096,为核电厂仪控系统各相关方提供了基于网络安全防范等级和生命周期阶段的具体指引,用于指导核电厂实施网络安全管控措施,以预防、检测和处置网络攻击。同时,等级保护制度作为我国网络安全的基础制度,是国内各核电厂必须开展的规定工作。为此,本文分别对IEC 63096以及等级保护系列标准进行了介绍,重点对二者在安全等级及管控措施方面的协调性进行了分析,从而帮助核电厂在进行网络安全管控措施的部署时有效降低时间成本和投资成本。

Bayesian belief-based model for reliability improvement of the digital reactor protection system

The digital reactor protection system(RPS)is one of the most important digital instrumentation and control(I&C)systems utilized in nuclear power plants(NPPs).It ensures a safe reactor trip when the safety-related parameters violate the operational limits and conditions of the reactor.Achieving high reliability and availability of digital RPS is essential to maintaining a high degree of reactor safety and cost savings.The main objective of this study is to develop a general methodology for improving the reliability of the RPS in NPP,based on a Bayesian Belief Network(BBN)model.The structure of BBN models is based on the incorporation of failure probability and downtime of the RPS I&C components.Various architectures with dual-state nodes for the I&C components were developed for reliability-sensitive analysis and availability optimization of the RPS and to demonstrate the effect of I&C components on the failure of the entire system.A reliability framework clarified as a reliability block diagram transformed into a BBN representation was constructed for each architecture to identify which one will fit the required reliability.The results showed that the highest availability obtained using the proposed method was 0.9999998.There are 120 experiments using two common component importance measures that are applied to define the impact of I&C modules,which revealed that some modules are more risky than others and have a larger effect on the failure of the digital RPS.

核电厂及周边辐射环境航空监测空地比对方法研究

核电厂辐射环境航空监测中进行空地比对是验证航测数据质量好坏的重要手段和方法,本次采用面积网格法,在研究区内的第四系沉积物区、基岩地层区和偏离测线及海陆交汇区域,选取多个监测点位开展空地比对分析,研究地面测量方法的有效性及位置选择的合理性。结果显示:第四系沉积物区监测比对点相对偏差在-8.8%~9.7%之间,基岩地层区监测比对点相对偏差在-9.1%~15.8%之间,偏离测线和海陆交汇区域比对点相对偏差在3.0%~44.3%之间。研究表明:面积网格法在辐射环境航空监测的空地比对研究工作中具有较好的应用性;在第四系沉积物区、基岩地层区域开展空地比对研究效果较好,可作为辐射环境航空监测空地比对地面选点的依据;受较多因素影响,偏离测线和海陆交汇区域比对效果较差,后续开展相关空地比对工作要重点研究和考虑。本次研究可为核设施辐射环境航空监测技术研究提供参考思路,也可为准确分析核设施及周边辐射环境变化趋势、核素迁移规律、核事故应急响应提供基础数据研究分析方法。

核电厂外围辐射环境监测数据异常自适应预警

针对核电厂周围的环境因素复杂多样和当前预警方法的虚警率较高的问题,提出核电厂外围辐射环境监测数据异常自适应预警方法。根据核电厂外围辐射环境监测数据的属性分布对数据进行修正处理,以提高数据的有效性。对于监测数据进行离散化分解,以获取数据属性的一阶滞后变量,结合数据之间的相似性度量识别数据的异常特征,并构建数据异常自适应预警模型,将模型输出的预警因子与预设值相比较,以此实现数据异常预警。以某核电厂运维系统作为研究案例对所提方法的预警性能进行测试,结果表明:该方法可以有效实现监测数据的异常预警,虚警率较低,预警效果好。

Reactor Protection Diversity Requirements and the Typical Solution Based on DCS

The defense-in-depth and diversity have become the basic requirements for digital I＆C and should be strictly followed when carrying out the overall scheme design of digital control system, in which the risk of common cause failure has to be prevented or coped with. This paper analyzes the requirements of the diversity principle and sums up the typical solution of the diversified protection of reactor based on the CPR1000 NPP. Some concepts will be helpful to the design of DCS for others plants.

2018—2023年防城港核电厂外围辐射水平分析

对防城港核电厂外围31个监测点位进行了γ辐射累积剂量率监测和γ辐射空气吸收瞬时剂量率监测,并对辐射水平监测结果进行分析,以掌握核电厂外围陆地辐射水平的长期变化状况。结果表明:2018—2023年,防城港核电厂外围环境γ辐射累积剂量率监测值为62.5~141.3 nGy/h,平均值为99.1 nGy/h;瞬时剂量率为55.0~119.5 nGy/h,平均值为93.7 nGy/h;防城港核电厂3台机组商运前后,外围陆地环境辐射水平保持一致,γ辐射累积剂量率、瞬时剂量率均保持在正常水平,核电运行期间气载流出物的排放对外围环境的辐射水平没有产生影响。不同点位的γ辐射累积剂量率变化较大,且随季节性变化呈冬季偏高、夏季偏低的现象,说明γ辐射累积剂量率受环境因素影响较大。

核电厂常规岛射线探伤对蒸汽厂房的辐射影响

由于核电站常规岛厂房设计的特殊性,地面以上厂房的大部分外墙由钢板搭建,加上厂房内管道和设备布置复杂,因此,射线探伤对蒸汽厂房区域的辐射影响较复杂。分析常规岛射线探伤对蒸汽厂房的影响,并提出了防护对策。

SVBR-100 Nuclear Technology as a Possible Option for Developing Countries

Many developing countries need ecologically clean power sources (PS). The nuclear power plants are such sources. However, a great number of the developing countries do not possess developed large capacity power systems. Moreover, currently in the developing countries, there are no highly skilled personnel to provide construction and reliable and safe operation of the nuclear plants, which are complex and potentially hazardous systems. In some countries, the level of terroristic threat is extremely high. For that reason, there are specific requirements to the nuclear PSs intended for use in the developing countries. In the presented report, the specific requirements which must be met by the NPT proposed for use in developing countries are formulated, basic statements of the SVBR-100 concept are presented, design and principal scheme of the reactor fa-ility are described, major characteristics of SVBR-100 are summarized.

核电厂流出物排放控制值研究

排放量控制是我国核电厂环境辐射防护和流出物排放管理的重要内容。通过对比国内外压水堆核电厂流出物排放量水平,分析了我国现行标准中排放控制值对国外同类核电厂流出物排放量的包络率,同时与法国流出物排放控制值进行了比较。结果表明,除流出物中^(3)H、^(14)C外,现有标准控制值基本上可以包络国外核电厂统计排放量,且具有较大的余量。在目前的流出物排放管理水平下,现行标准中规定的排放量控制值仍是适宜的,其中对于^(3)H、^(14)C外的其他控制指标仍有很大的优化空间。

福清核电厂5^(#)、6^(#)机组反应堆保护系统的设计

反应堆保护系统是核电厂应对预期运行事件或设计基准事故而设置的重要安全级仪控系统。为满足“华龙一号”三代核电高安全性目标的设计要求,需要对反应堆保护系统的功能性能进行提升。以“华龙一号”示范工程福清核电厂5#、6#机组为研究对象,通过充分考虑保护系统设计准则要求并基于事故分析结论,提出了更具高可靠性和全面保护功能特征的反应堆保护系统设计方案。详细介绍了系统自动保护功能的设计、系统结构设计以及系统健康管理等内容,并对系统拒动率进行了定量分析。分析结果表明,系统总体拒动率不高于5.0×10^(-7)/指令,达到了国际主流三代核电的可靠性水平。该研究成果可为后续核电厂的反应堆保护系统设计或优化提供借鉴。

核电厂调试阶段仪控系统隐患分析方法研究

仪控系统是核电厂的神经和大脑,对于核电厂的安全、高效运行起着至关重要的作用。仪控系统中容易潜藏一些未能在工厂测试期间发现的隐患。这些隐患在运行过程中可能导致核电厂设备的功能劣化甚至系统故障。核电厂仪控系统的调试过程是运行前的关键阶段,在调试过程中及时识别隐患对于保证仪控系统的正常运行具有重要意义。首先,从特定应用环境、特定应用方式、长期动态运行三个维度对隐患的激发原因进行了分析。对其中可能在调试阶段产生、暴露的隐患激发原因进行了筛选。然后,以核电厂仪控系统实际调试过程中发生的隐患为例,建立隐患与环境模型的映射关系模型,并验证模型在调试阶段的有效性。该研究有助于提高调试阶段核电厂仪控系统隐患的识别能力,具有重要的工程意义。

Clearing of the Radioactive Liquid Waste from Oils and Oil Products by UV-Radiation at NPPs

The basic methods of concentration and purification of liquid radioactive waste on the nuclear power plant are distillation and ionic exchange. During vaporization of oil waste products and the fulfilled washing solutions the part of oil passes into a condensate. Clearing of such condensate on ion-exchanged filters results to oiling of ion-exchanged materials and to decrease number of filter cycles. Due to the often regeneration of ion-exchanged filters additional volumes of waste products as the fulfilled reclaiming solutions, washing and loosening waters are formed. The attention of scientists was involved with methods of clearing of water environments from the organic substances, based on deep oxidizing transformations of hydrocarbons into carbonic gas and water. From processes of oxidation of hydrocarbons up to CO2 and H2O, sold at moderate conditions, our attention has involved photochemical oxidation with the help of UV-radiation.