Transient Analysis of a Reactor Coolant Pump Rotor Seizure Nuclear Accident

The reactor coolant pump(RCP)rotor seizure accident is defined as a short-time seizure of the RCP rotor.This event typically leads to an abrupt flow decrease in the corresponding loop and an ensuing reactor and turbine trip.The significant reduction of core coolant flow while the reactor is being operated at full load can have very negative consequences.This potentially dangerous event is typically characterized by a complex transient behavior in terms of flow conditions and energy transformation,which need to be analyzed and understood.This study constructed transient flow and rotational speed mathematical models under various degrees of rotor seizure using the test data collected from a dedicated transient rotor seizure test system.Then,bidirectional fluid-solid coupling simulations were conducted to investigate the flow evolution mechanism.It is found that the influence of the impeller structure size and transient braking acceleration on the unsteady head(Hu)is dominant in rotor seizure accident events.Moreover,the present results also show that the rotational acceleration additional head(Hu1)is much higher than the instantaneous head(Hu2).

Checking of seismic and tsunami hazard for coastal NPP of Chinese continent after Fukushima nuclear accident

A checking on seismic and tsunami hazard for coastal nuclear power plant (NPP) of Chinese continent has been made after Japanese Fukushima nuclear accident caused by earthquake tsunami. The results of the checking are introduced briefly in this paper,including the evaluations of seismic and tsunami hazard in NPP siting period,checking results on seismic and tsunami hazard. Because Chinese coastal area belongs to the continental shelf and far from the boundary of plate collision,the tsunami hazard is not significant for coastal area of Chinese continent. However,the effect from tsunami still can't be excluded absolutely since calculated result of Manila trench tsunami source although the tsunami wave is lower than water level from storm surge. The research about earthquake tsunami will continue in future. The tsunami warning system and emergency program of NPP will be established based on principle of defense in depth in China.

Radioactive source terms for the Fukushima nuclear accident

A large amount of radioactivity was released into the environment after the Fukushima nuclear accident （FNA） in Japan in 2011. This radioactivity had a significant impact on the global environment, and there was much public concern about its effects. The subsequent assessment of the FNA and the environmental remediation required are proving to be long and complicated tasks. The assessments are based on the radioactive source terms for the FNA, which determine the level of damage caused by the nuclear accident. We investigated the radioactive source terms from three aspects： the amount and composition of the radionuclides; the activity and atomic ratio of the radionuclides; and comparison with other historical events. The total amount of radioactivity, excluding the radioactive noble gases （85Kr and 133Xe）, released by the FNA was about 10% of that released by the Chernobyl nuclear accident in 1986 and 〈1%o of the global fallout from the atmosphere nuclear explosion. However, the FNA was the most serious nuclear accident in terms of radioactive pollution of the marine environment. The recovery actions carried out after the FNA have been evaluated and the environmental impacts of the FNA are discussed.

The comparison of ensemble or deterministic dispersion modeling on global dispersion during Fukushima Dai-ichi nuclear accident

Ensemble forcasting,originally developed for weather prediction,is lately being extended to atmospheric dispersion applications,which is a new,effective methodology for improving the atmospheric dispersion numerical modeling.In March 2011,due to the massive 9.0 earthquakes and ensuing tsunami that struck off the northern coast of the island of Honshu,the Fukushima Nuclear Plant I had the substantial leak of radioactive materials into surrounding environment and atmosphere.To aim at the global dispersion modeling of atmospheric radionuclides from Fukushima Nuclear Accident,this paper presents two approaches of atmospheric dispersion forecasting:ensemble dispersion modeling(EDM) and deterministic dispersion modeling(DDM),conducts the globally dispersion modeling cases for Fukushima nuclear accident,and analyzes and evaluates the simulation results using observation data.In this paper,EDM includes three different perturbation methods:meteorological perturbation method,turbulence perturbation method,and physical parameterization ensemble forecasting method.The simulation results show that the trajectories from EDM have a better performance,which is in better agreement with the atmospheric circulation and observation data; the spread from DDM is slower and not as far as EDM.Additionally,the results from EDM display a better performance in the modeling of transport from Japan to China East Sea on April 4.The reasons for these results are:the techniques of MET and TUR are performed by adding perturbations on mean wind and turbulent velocity,respectively; the various different flow fields will result in far spreading in horizontal and the simulation results closer to observation; PHY is performed by using different diffusion physical parameterizations and produces the perturbations on vertical wind,which results the spreading in smaller range and discontinuous in horizontal.Finally,the comparative analysis between modeling results and observation data shows that all cases results are in good agreement with trends of observed radionuclides surface concentration; however,the modeling surface concentration is smaller than observation,especially in DDM and PHY.Furthermore,the EDM results show that MET and TUR are of more evolutionary advantage than PHY in modeling of average and maximum concentration.Therefore,this study can serve as a reference to atmospheric dispersion and environmental emergency response(EER).

A dynamic food-chain model and program for predicting the consequences of nuclear accident

A dynamic food chain model and program, DYFOM 95, for predicting the radiological consequences of nuclear accident has been developed, which is not only suitable to the West food chain but also to Chinese food chain. The following processes, caused by accident release which will make an impact on radionuclide concentration in the edible parts of vegetable were considered: dry and wet deposition interception and initial retention, translocation, percolation, root uptake and tillage. Activity intake rate of animals, effects of processing and activity intake of human through ingestion pathway ware also considered in calculations. The effects of leaf area index LAI of vegetable were considered in dry deposition model. A method for calculating the contribution of rain with different period and different intensity to total wet deposition was established. The program contains 1 main code and 5 sub codes to calculate dry and wet deposition on surface of vegetable and soil, translocation of nuclides in vegetable, nuclide concentration in the edible parts of vegetable and in animal products and activity intake of human and so on.

Obstetric Outcomes in Women in Fukushima Prefecture during and after the Great East Japan Earthquake and Fukushima Nuclear Power Plant Accident: The Fukushima Health Management Survey

Objective: The Great East Japan Earthquake (magnitude, 9.0) followed by a large-scale tsunami caused a severe nuclear accident at the Fukushima Daiichi Nuclear Power Plant (Tokyo Electric Company). This study aimed to evaluate the obstetric outcomes in women in Fukushima prefecture during and after the Great East Japan Earthquake and Fukushima nuclear power plant accident. Methods: We collected information for 12,300 pregnant women who conceived during the 9 months before and after the disaster in Fukushima prefecture. The data of the subjects were analyzed according to the conception date for each pregnancy. Results: Among the women who conceived within 9 months before the disaster, adverse obstetric outcomes were not observed. In contrast, in the case of women who conceived within 6 months after the disaster, an increase in the incidence of preterm birth (less than 37 weeks) and low birth weight (less than 1500 g and less than 2500 g) was observed. Moreover, these women showed an increased incidence of medical complications, such as respiratory diseases and mental disorders. Conclusion: The results of the present study show that the occurrence of adverse obstetric outcomes was higher in the women who conceived within 6 months after the disaster than in those who were pregnant at the time of the disaster. The results may be related to emotional stress such as anxiety about the disaster and emphasize the need for continued investigations and careful management of pregnant woman in disaster areas in the future.

Advance on monitoring of radioactivity in food in China and Japan after Fukushima nuclear accident

After the nuclear accident at the Fukushima Daiichi Nuclear Power Plant(Fukushima nuclear accident)in 2011,Japan quickly took emergency measures to reduce radiation hazards posed by the released radioactive materials.As a neighboring country of Japan across the East China Sea,China has also taken some corresponding prevention and control measures.China has continuously strengthened the monitoring of radioactivity in food in recent years.This paper discusses the revision of standards for radioactivity in food,the improvement of methods and equipment,and the updating of monitoring systems performed in China and Japan over the last ten years after the Fukushima Daiichi accident.In addition,this paper outlines the recent problems left over from the nuclear accident,puts forward some views on the progress of important topics,and gives some thoughts and prospects on the further improvement of the monitoring systems of radioactivity in food in China.

Impact Analysis of the 2011 Fukushima Nuclear Power Plant Accidents by Running Spectrum Analysis on Newspaper

Huge amount of digital data of the Great East Japan Earthquake is provided by the highly-developed digital data technology. But the method and technique for analysis of these huge digital data are not developed sufficiently. This paper proposes a running spectrum technique for text data and analyzing changes of disaster phase during the disaster management cycle. Impact analysis of the nuclear power plant accidents have been performed by using Fukushima Minpo newspaper for its verification. The result shows the dynamic characteristics of the nuclear power plant accidents. As the time interval B becomes longer, the analysis data is used from wide range period along with the smoothing effect. When observing different time intervals B, fewer keywords have been ranked in the longer time intervals of B. The proposed technique is a powerful tool to effective and efficient disaster response and management. analyze effectively the huge amount of digital data for the

Nuclear Power and Radioactive Contamination

Nuclear power was designed to produce electric power. Each part of the chain from uranium mining to handling of the waste is linked to serious contamination risks, however. Uranium mining is generally linked to local to regional contamination. The fuel production also produces depleted uranium at a ratio of 1:7. The reactors are operating under danger of accidents. Numerous minor accidents and endless temporary shut-downs are occasionally mixed with disastrous accidents. The Chernobyl (1986) and Fukushima (2011) accidents are notorious. The radioactive contamination from those accidents is still incomprehensible and will keep serious destructions of the environment for centuries to come. The handling of the high-level nuclear waste remains unsolved. Methods proposed in Sweden, Finland and France seem likely to lead to disastrous radioactive contaminations in the future. The only way out of this dilemma seems to be a disposal where the waste, though effectively sealed-off in the bedrock, remains accessible and controllable. At present, the “cost & benefit” balance seems strongly tilted over to the “far too costly side”, however.

中法关于核能与环境的联合研究

本文聚焦核能的环境影响问题,将解决如下核能发电相关的主要环境问题:(1)控制正常运行条件下核设施的放射性排放,评估其非放射性环境影响(取水与非放射性水的排放);(2)乏燃料与放射性废物的长期管理,主要是通过地质处置库处理的乏燃料或放射性废物;(3)防止和缓解严重核事故以及核事故的放射性释放;(4)改善核安全水平,以限制核能的环境影响,提升公众的核能接受度。核能的温室气体排放水平非常低,可以根据需求供应大规模、可调度电力,在此方面核能具有独特的优势。在正常运行工况下,核电站每年释放到周围公众的有效辐射剂量可以忽略不计。国际社会已经开展了大量的努力,以确定可持续管理地质处置条件下高放长寿命放射性废物的方法。过去几次严重核事故中获得的经验为核能生产相关的安全问题提供了经验,也促成了重要的安全改进,其中包括反应堆的设计和运行管理方面的改善以及事故管理指导方针的制定等。事实证明,这些经验是非常宝贵的。严重事故的环境风险已经被大幅降低,相关的规约也已经建立起来,以最大限度地减少严重核事故条件下放射性物质的释放,并避免大规模的人员疏散。还需要继续采取措施,改善反应堆的安全性,提升核工业与核监管机构的透明度,以进一步降低核能的环境影响。

Levels and behavior of environmental tritium in East Asia

For a more systematic understanding of the levels of environmental tritium and its behavior in East Asia,a database on environmental tritium was established based on the literature published in the past 30 years.Subsequently,the levels and behavior of the environmental tritium were further studied by statistical analyses.The results indicate that the distribution of environmental tritium is inhomogeneous and complex.In areas without nuclear facilities,the level of environmental tritium has decreased to its background level,even though a certain number of atmospheric nuclear tests were performed before 1980.In general,the level of atmospheric tritium was marginally higher than the levels in precipitation and surface water;the levels in shallow groundwater and seawater were considerably lower.Furthermore,the levels of tritium in the atmosphere,precipitation,and inland surface water were strongly correlated with latitude and distance from the coastline.In soil and living organisms,the level of tissue-free water tritium(TFWT)was comparable to the tritium levels in local rainfall,whereas the persistence of organically bound tritium(OBT)in the majority of organisms resulted in an OBT/TFWT ratio greater than one.Conversely,extremely high levels of environmental tritium were observed near certain nuclear power plants and the Fukushima accident sites.These results highlight the requirement to know the tritium baseline level and its behavior in the environment beforehand to better assess the impact of tritium discharge.Further investigations of environmental tritium in East Asia using more efficient and adequate monitoring methods are also required.

Monitoring long-term ecological impacts from release of Fukushima radiation water into ocean

After 10 years of the Fukushima Nuclear Accident,Japan decided to release the nuclear wastewater into the Pacific Ocean on 13 April 2021.It is apparent that Japan has chosen the most cost-efficient way to deal with the contaminated water,however,great opposition and concerns have been raised internationally due to the ecotoxicological features of radioactive materials and their harmful impacts on the environment.Here we an-alyze the ecological impacts caused by the nuclear accident and the potential impacts of releasing the nuclear wastewater into the ocean.Science-based solutions are proposed through a third-party evaluation and strict envi-ronmental assessment,multi-stakeholder public participation,integrated monitoring of the neighboring coastal countries,long-term international collaborative research,and setting up international convention for ecological compensation.

田湾核电站场外事故后果评价系统——TW-NAOCAS

从田湾核电站早期应急的需要,开发了一套核事故场外后果实时评价计算机系统软件(TW-NAOCAS)。该系统设计为一个连接多种模型(数据预处理、风场预测、大气弥散、剂量估算和干预与防护对策评估)和数据库的综合系统。本文对该系统进行介绍,并通过模式比对,对系统物理模型有效性进行了初步分析。结果表明,该系统采用的物理模型和运行设计是有效而可靠的。

Study on Sampling Technique of Atmospheric Radionuclide

Atmospheric radionuclide monitoring usually includes two sampling techniques, namely ultra-high volume aerosol samplers to collect at- mospheric particles by using filter media, and radioactive noble gas samplers to collect atmospheric noble gas based on adsorption method. Atmos- pheric sampling techniques have been researched in Northwest Institute of Nuclear Technology since the Comprehensive Nuclear-Test-Ban Treaty （CTBT） was signed in 1996. Several ultra-high volume aerosol samplers and some types of radioactive xenon isotopes samplers had been devel- oped. For the aerosol sampler, the sampling flow is between 450 and 800 m3/h, with the minimum detectable concentration （MDC） of 131I less than 5 pBq/m3. For the xenon sampler, the sampling capacity of xenon is more than 4 ml per day, with MDC of l=Xe less than 0.25 mBq/m3. After the nuclear accident of Fukushima in 2011, monitoring of the atmospheric radionuclide was carried out for 3 months at Xi＇an, and part of radionuclide was detected with concentrations hiaher than their backorounds in the period, includina 131I.134Cs. 137Cs and 133Xe.

核电厂常规岛主厂房超设计基准荷载效应探讨

核电厂中聚集着大量的放射性物质,如果一旦遭受到破坏可能导致放射性物质外泄,将会对公众的生命和健康造成威胁。如果反应堆系统遭到破坏,将会造成影响范围更广的核事故。而核电厂常规岛主厂房作为一种非常重要且特殊的工业建筑,其结构设计强度相当高,但是不免有超设计基准荷载发生,例如偶然荷载的冲击,会使核安全设计的多重性和多样性防护准则受到破坏,结构一旦发生破坏,特别是靠近安全壳的一侧发生破坏,将会直接威胁到核岛得安全,进而可能造成核泄漏等毁灭性问题。因此,本文从超设计基准方面来考虑核电厂常规岛主厂房的荷载设计值。

Application of Microscopic Simulation of Traffic Flows in Developing Evacuation Plans for Inhabitants

The paper presents the possibilities of implementing micro-simulation traffic tools in order to develop the evacuation plans. Well elaborated evacuation plans are the basis for alleviating the consequences resulting from emergencies. The simulation tools allow the design and verification of various evacuation planning scenarios with minimisation of costs and time. The paper provides detailed presentation of the basic characteristics of microscopic simulation of traffic flows, as well as examples of their implementation worldwide. The characteristics of the software tools are described through an overview of the basic settings ofPTV VISSIM （Planung Transport Verkehrin Stadten--Simulations model） program as one of the most significant representatives of these tools. The necessity of implementing the traffic tools in evacuation results from the crucial role of traffic in reducing the consequences of emergencies. These tools allow also a detailed analysis of the output data in order to select a suitable solution. The concluding part of the paper presents an example of evacuation of the population through the Jankomir node as part of the European project ＂preparedness for evacuation in case of a nuclear accident＂. The evacuation was performed through three scenarios in circumstances of higher or lower transport demand.

广东省核电站核事故场外后果预测评价系统

广东省核电站核事故场外后果预测评价系统 (GNARD2 .0 )是一个核电站事故场外辅助决策计算机软件系统 ,该系统具有在线和实时评价和预测事故后果的能力 ,能够计算风场、放射性物质浓度和剂量 ,进而给出超过干预水平的区域及区域内的人口、应急设施等信息 ,并能对应急防护行动实施进程进行模拟和计算 ,得出可防止剂量以评价行动的有效程度。本文简要介绍了该系统的软硬件组成和后果评价模式 ,总结了系统开发经验 。

核电站控制棒意外下落事件分析与处理

针对田湾核电站控制棒移动过程中意外下落至堆芯底部且无法正常提升事件,通过对控制棒驱动机构供电模件、电磁线圈电气回路、驱动机构部件等的分析,找出故障原因,保障机组的安全稳定运行。

Text Mining Analysis of Efficiency of the Continuously Implemented Gathering Type Action Plan for Male Elderly People Obtained

Aim: To clarify transformation of the participants’ consciousness for rebuilding the community and its factors from the discussion contents by actions for male elderly people in Town A in Fukushima prefecture. Design: This study was an action research. Method: The author verbalized discussion contents of the action conducted in 2018-2019 and analyzed them for each year by the text mining method. Results: The word appearance frequency was high in the order of “Person” and “Town A” in both years. One large word network was formed in 2018 and its topic was about what the participants feel in their life in Town A. Two large word networks were formed in 2019 and their topic was about the community participation including difficulty in motivating others such as how people who do not participate can feel like joining it.

基于人因工程的核电厂防误碰分析与设计

误碰类人因事件是国内外核电机组高偶发性人因事件的类型之一。为了预防人因事件的发生、保证机组安全稳定运行,对已发生的误碰类人因事件进行深入分析,在设计阶段就考虑防误碰措施对核安全有重要意义。通过跟踪和研究国内外核电机组误碰类人因事件,对误碰类人因事件进行二级分析,整理出易造成误碰的工作类型和易误碰设备,确定了误碰类人因事件的主观因素和客观因素。根据国内外同行及群厂的经验反馈和良好实践,依据防人因失误管理的先进理念,提出了防误碰改进措施和建议。从设计的角度出发,提出了设计阶段的系统设计、设备选型和现场布置阶段的预防措施,从而减少误碰风险点,预防误碰类人因事件的发生,确保核电机组安全稳定运行。如果新的核电厂在设计之初就采用防误碰的改进措施和建议,核电厂建成后可以有效预防误碰事件的发生。误碰类人因事件的防御研究对核电厂全厂人因失效防御研究有重要的借鉴和指导意义。