Boussinesq近似对于爆炸烟云运动数值计算的影响

采用Boussinesq近似模型与不可压缩模型研究了不同密度比的烟团在标准分层大气条件下的烟云运动过程,分析了两种模型计算烟云之差异,得出烟团密度与周围大气密度比越小,两种模型计算结果相差越大的结论,当密度比达到0.9时,两种模型计算结果基本一致,为研究爆炸烟云的运动提供参考。     

地铁站内脏弹爆炸烟团扩散的仿真研究

针对地铁站内脏弹爆炸烟团扩散问题,以计算流体力学(CFD)为理论基础,用FLUENT软件建立离散相模型(DPM)进行数值仿真。通过比较不同的爆炸载荷系数β和通风系统,分析了不同装药的脏弹对爆炸产生的PM₁₀粒子在室内运动的规律和浓度,同时进一步研究了通风系统对颗粒扩散的影响,为脏弹恐怖事件的辐射防护和应急救援提供源项参考。     

核电厂事故应急局地实时剂量评价系统的模式与参数

本文介绍在核电厂事故应急局地实时剂量评价系统中应用的拉格朗日烟团模式及相应的参数。对烟团轨迹考虑了事故期间风向、风速的变化,采用有效扩散参数以考虑烟团迁移期间大气稳定度等气象条件的变化,干沉积采用源耗减模式,湿沉积采用冲洗系数方法,还考虑了放射性衰变及烟团部分穿透混合层的修正。鉴于我国在建核电厂皆位于沿海地区,文中还给出了内边界层条件下烟团公式的处理方法。对于实时剂量评价,主要考虑了烟云浸没外照射、吸入内照射和沉积放射性核素外照射三种照射途径。最后,以秦山核电厂为例估算了 PWR1事故的环境影响,给出了部分计算结果。     

核爆炸放射性沉降预警模型研究

采用简化动力学方法建立了核爆炸烟云上升模型,采用MC法和Gifford对流层相对扩散理论建立了烟云扩散模型,推导出了放射性云浸入空气吸收剂量和地面沉降空气吸收剂量模型;给出了在不同当量地表面爆炸和典型气象条件下,下风方向不同距离放射性沉降到达时间和剂量率。分析研究表明:在已知核爆炸当量和气象参数的条件下,可以实现对核爆炸放射性沉降的预警;核爆炸烟云浸没剂量率不可忽略,在烟云过顶时超过了地面沉降剂量率。     

聚变堆失真空事故下氚的大气扩散模拟研究

聚变反应堆发生失真空事故的情况下氚会泄漏到环境中，氚大气扩散模拟是聚变堆事故后果评价的重要内容。基于高斯烟团模型以及Pasquill稳定度分类方法，考虑重力沉降、烟气抬升、风速等因素的影响，建立了适用于事故下瞬态分析的大气扩散模型，在高斯烟团模型中加入修正了像源贡献的地面反射系数，提高了模型对于地面边界处干沉降的计算效果。选取加拿大氚气释放实验和美国萨凡那河工厂氚释放事故验证了所建立模型的准确性，模型的计算结果与HotSpot 3.0和UFOTRI软件的精度相当。选取国际热核聚变实验堆（International Thermonuclear Experimental Reactor,ITER）的失真空事故作为研究对象，分析了氚的分阶段释放、风速以及释放高度对氚扩散分布的影响。结果表明：氚的分阶段释放会导致沿下风向出现两个高放射性区域；释放高度和风速的增加会强化氚在大气中的扩散行为，从而减弱放射性在近场的积聚。     

内陆代表性厂址事故扩散因子不同估算方法的比较

针对内陆核电选址中小风、静风频率较高的厂址,分别采用美国核管会(NRC)导则推荐方法和运用三维客观诊断风场与Lagrangian烟团模型模拟整年8 760小时逐时排放方法,计算了湖南桃花江厂址事故工况下的大气扩散因子,探讨复杂条件下大气扩散模型的适宜性。研究表明:在非居住区边界概率论方法计算的最大小时事故扩散因子较烟团模型计算方法保守;Lagrangian烟团模型计算的小时事故扩散因子在某些方位大于概率论方法结果,某些远距离子区的扩散因子大于近距离子区;对于释放时间相对较长的情形,导则方法估算结果仍偏小。由此可见,导则推荐方法得到的扩散因子存在不保守的情形,建议在计算复杂地形、小静风频率较高的内陆厂址事故扩散因子时慎重选择扩散模型。     

小型动力堆海上核事故后放射性核素在大气和海洋中扩散研究

为准确评估小型动力堆海上严重核事故后释放的气载核素造成的海洋放射性污染水平,以小型动力堆断电诱发的严重核事故为例,建立核素在大气和海洋中扩散的计算模型,计算事故后大气和海洋中137Cs的放射性污染水平,并分析了气载核素释放高度、大气稳定度对沉降核素海洋扩散的影响。结果表明,在一定的释放高度下,源下风轴线上表层海水中核素的时间积分浓度随下风向距离的增大呈先升高后下降的变化规律;在离源一定距离内,释放位置越高,表层海水中核素的时间积分浓度越小;在离源一定距离外,大气越不稳定,表层海水中核素的时间积分浓度越小。      

压水堆最大可信事故及其辐射剂量估算方法(续)

反应堆最大可信事故的环境危害主要是由气载放射性造成的。在计算辐射剂量前,须先了解放射性烟云的大气扩散和沉积规律,须用扩散气象学的知识。事实上,扩散气象学也是反应堆安全研究的一个重要组成部分。 关于放射性烟云的大气扩散规律已进行了大量的理论和实验研究。特别是中小尺度     

秦山核电厂实时剂量评价系统的设计,模式,参数与程序

本文介绍应用于秦山核电厂事故应急的实时剂量评价系统的设计、模式、参数与程序。该评价系统由实时数据采集系统、评价计算机系统和评价程序系统三部分组成。评价系统采用地形随动座标的质量守恒三维风场诊断模式来确定每小时的地面和低空风场；大气扩散计算采用变天气条件下的烟团模式，计算区域分近、中、远三区；烟团释放采用分阶段变长度方式，外照射剂量估算采用了半无限烟云与有限烟云两种模式，该评价系统可在输入数据后约１     

随机游走大气扩散模型在核事故应急中的开发和应用

烟羽浓度预测是核事故早期应急响应放射性后果评价系统的主要内容之一.描述了大气扩散本身随机的特点,介绍了自行开发随机游走大气扩散模型Random Walk,并与现有欧共体开发的核应急决策支持系统RODOS中的拉格朗日烟团模型RIMPUFF进行比较验证.结果表明,两者计算结果相当吻合,但Random Walk计算出的烟羽范围比RIMPUFF计算出的稍小.随机游走大气扩散模型Ran-dom Walk能够较好的模拟核事故发生条件下的大气扩散过程,可以作为核事故应急决策系统的一个大气扩散模块,为早期应急和后果评价提供更接近实际的信息.     

确定核电厂气载放射性流出物排放限值的设计方法研究

为了使核电厂的气载放射性流出物排放所致环境公众辐射剂量满足法规标准要求,本文从辐射防护剂量限值、大气污染物扩散规律及核电厂源项特点等方面考虑,通过实例分析,探讨了确定核电厂气载放射性流出物排放限值(排放率、排放浓度、地面浓度限值)的设计方法,提出了限值的建议值,并与已有核电厂的气载流出物排放报警阈值进行了验证,确认了方法的合理性。     

核辐射突发事件医学应急的现场救援及组织指挥原则

根据核辐射突发事件医学应急现场救援的具体任务和需要的处置力量,将其分为小规模核辐射突发事件、中等规模核辐射突发事件和大规模核辐射突发事件,并具体分析了各自的特点、危害、现场医学救援的任务和技术力量。重点针对＂脏弹＂恐怖袭击,介绍了现场医学救援的主要任务,以及污染控制和伤员救治的技术流程。为更好地执行核辐射事故现场医学救援任务,总结并提出了组织指挥中应该注意的几个原则,包括快速反应原则、剂量限值原则、防护最优化原则、权衡利弊原则,以及辐射监测、去污控污、伤员救治等核心任务的全流程贯穿原则等。     

Estimation of the resident''s additional dose in bone-coal mining areas of the five provinces

This paper introduces the resident's additional dose in bone-coal mining areas. The increase of the annual additional effective doses accepted by the residents living in the carbide-brick houses, the staffs working in the carbide-brick houses and the miners working in the bone-coal mining areas of Hubei, Hunan, Jiangxi, Zhejiang and Anhui Provinces is caused by the rising of environmental radioactive level. The investigation of natural background radiation in the bone-coal mining areas indicated that both mining and utilizing bone-coal cause the rise of environmental radioactive level. The ranges of the annual additional effective dose accepted by the residents, staffs and miners is 1.9-6.8 mSv, 0.5-2.0 mSv and 8.2-71 mSv, and with an average of 3.8 mSv, 1 mSv and 40 mSv, respectively. The annual additional effective doses accepted by part residents and staffs exceed the dose limit of 1 mSv for public exposure, and part miners exceed the dose limit of 20 mSv for occupational exposure. And the contribution of dose caused by inhaled radon to the total additional effective dose is over 76%.     

Harmful effects of the radioactivity from explosion of pure hydrogen bomps and ordinary atomic bombs

An evaluation is made of the dangers to the population from long-lived radioactive products distributed over the whole globe after the explosion of an ordinary (fission) bomb and a pure hydrogen (fusion) bomb. The pure hydrogen bomb considered is a deuterium-tritium bomb.Gonad and bone doses are calculated, with the resulting numbers of births with hereditary diseases and cases of leukemia (blood cancer). In the case of a hydrogen bomb the active elements are C¹⁴ and H³, and for an ordinary bomb they are Sr⁹⁰, Cs¹³⁷ and C³⁴. The distribution of the radioisotopes in nature and in the organism is evaluated. The case of s ground burst of a hydrogen bomb is also considered. The total amount of energy from the radioactive decay of the explosion products of a deuterium-tritium bomb is greater by s factor of three than that for an ordinary bomb. The radiation dose to the tissues and the number of victims to radioactive fallout over all time are about the same for 10 megatons TNT equivalent of both types of bombs, These doses are (rounded off): Thus in terms of the radiation damage caused to the world population, a pure hydrogen (deuterium-tritium) bomb cannot be considered less dangerous than an ordinary bomb.The author considers it his pleasant duty to thank A. P. Vinogradov, N. P. Dubinin, V. M. Klechkovskii, A. V. Lebedinskii, and A. D. Sakharov for valuable discussion of the questions considered, and for advice.     

Harmful effects of the radioactivity from explosion of pure hydrogen bomps and ordinary atomic bombs

An evaluation is made of the dangers to the population from long-lived radioactive products distributed over the whole globe after the explosion of an ordinary (fission) bomb and a pure hydrogen (fusion) bomb. The pure hydrogen bomb considered is a deuterium-tritium bomb. Gonad and bone doses are calculated, with the resulting numbers of births with hereditary diseases and cases of leukemia (blood cancer). In the case of a hydrogen bomb the active elements are C¹⁴ and H³, and for an ordinary bomb they are Sr⁹⁰, Cs¹³⁷ and C³⁴. The distribution of the radioisotopes in nature and in the organism is evaluated. The case of s ground burst of a hydrogen bomb is also considered. The total amount of energy from the radioactive decay of the explosion products of a deuterium-tritium bomb is greater by s factor of three than that for an ordinary bomb. The radiation dose to the tissues and the number of victims to radioactive fallout over all time are about the same for 10 megatons TNT equivalent of both types of bombs, These doses are (rounded off):

     

Development of LOcal-scale High-resolution atmospheric DIspersion Model using Large-Eddy Simulation. Part 5: detailed simulation of turbulent flows and plume dispersion in an actual urban area under real meteorological conditions

We have developed a LOcal-scale High-resolution atmospheric DIspersion Model using Large-Eddy Simulation (LOHDIM-LES) to assess the safety at nuclear facilities and to respond to emergency situations resulting from accidental or deliberate releases of radioactive materials (e.g., a terrorist attack in an urban area). In parts 1–4, LESs of turbulent flows and plume dispersion over a flat terrain, around an isolated building, within building arrays with different obstacle densities, and within an actual urban area were performed, which showed the basic performance comparable to wind tunnel experimental technique. In this study, we extend the LOHDIM-LES to turbulent flows and plume dispersion in an actual urban area under real meteorological conditions by coupling with a meso-scale meteorological simulation model. The LES results of wind speed, wind direction, and concentration values are generally reproduced well. It is concluded that our coupling approach between LES and meso-scale meteorological models is effective in detailed simulations of turbulent flows and plume dispersion in urban areas under real meteorological conditions.     

Dose Rate Measurements Around Consignments of Radioactive Material

Abstract

The International Atomic Energy Agency' (IAEA) Regulations for the Safe Transport of Radioactive Material require compliance with various radiation protection control measures and also require the competent authority to arrange for periodic assessments of the radiation doses to workers and to members of the public. It is a two-fold approach of controls and assessments. Periodic reviews of the radiological impact arising from the transport of radioactive materials by road, rail, sea and air, have been undertaken by NRPB on behalf of the UK Competent Authority. Dose assessments were made using estimated exposure times together with measured and extrapolated dose rates from ‘near-field’ regions close to consignments, ‘mid-field’ regions occupied by transiently exposed persons and ‘far-field’ regions occupied by members of the public. The results show that annual doses to workers and public are generally small fractions of dose limits. The exception is a small group of driver/handlers involved with packages for medical and industrial use. Compliance with the Regulations has ensured that a sufficient degree of control exists. Originally, most packages were small compared with the distances to exposed persons. Point source geometry was therefore used. More recently, it has been estimated that only a minority of all consignments of radioactive material is of sufficiently small dimensions for point source geometry to continue to apply. Instead, initial despatches of radionuclide packages can consist of consignments of several cubic metres in size, and only at tertiary despatch level would point source geometry prevail. However, for all physically large loads, the measured dose rates do not decline as rapidly as point source geometry would suggest based on the TI value. Development of the methodology adopted by the IAEA Regulations over some 40 years has introduced parameters to compensate in part for these levels of dose rate, and, together with operational improvements in transport procedures and practices, have ensured that annual doses remain low, well below dose limits. The methodologies employed for Regulatory control measures and those for assessment of annual doses, differ with the former based on robust and conservative models. For dose assessment purposes, realistic data are used based on measured dose rates and exposure times.     

小型动力堆码头中破口失水事故大气扩散研究

采用高斯分段烟羽模型估算了某小型动力堆在码头内发生破口尺寸为29.4%当量直径的设计基准事故时,放射性核素在码头20 km区域范围内的大气扩散规律。源项采用严重事故计算程序MELCOR仿真获得,并将计算结果输入到大气扩散分析软件MACCS进行分析计算。计算结果表明：中破口失水事故会造成码头区域的放射性污染,风速越小、气象条件越稳定,放射性的影响范围越大。     

Fission product release and its environment impact for normal reactor operations and for relevant accidents

The radioactive concentration in the primary loop and the radioactive release for both normal operations and accidents for the HTR-10 are calculated and presented in the paper. The coated-particle fuel is used in the HTR-10, which has good performance of retaining fission products. Therefore the radioactive concentration in the primary loop of the HTR-10 is very low, and the amount of radioactive release to the environment is also very small for both normal operation and accident conditions. The radiation doses to the public caused by radioactive release for both normal operations and accidents are given in the paper. The results show that the maximum individual effective dose to the public due to the release of airborne radioactivity during normal operations is only 1.4×10⁻⁴ mSv a⁻¹, which is much lower than the dose limit (1 mSv a⁻¹) stipulated by Chinese National Standard GB8703-86. For depressurization accident and water ingress accident, the maximum individual whole-body doses to man are only 7.7×10⁻² and 2.0×10⁻¹ mSv, thyroid doses only 1.7×10⁻¹ and 1.1 mSv, respectively. They are much lower than the prescribed minimum of emergency intervention level (whole-body dose: 5 mSv, thyroid dose: 50 mSv) for sheltering measures stipulated by the Chinese Nuclear Safety Criterion HAD002/03. The conclusion is that the environmental impact is very small for normal operations and accidents for the HTR-10, and the requirements stipulated in the Chinese Nuclear Safety Criterions are satisfied perfectly.     

低放固体废物核素活度浓度上限值的推导

介绍了近地表处置设施在300 a监护期前及其以后的任何时间,公众个人及闯入者通过各种途径的受照剂量分别小于剂量限值时所要求的低放固体废物核素活度浓度上限值的推导方法及过程。以我国放射性废物近地表处置的基本安全要求为前提,并以遥田处置场和北龙处置场为对象,分析处置设施关闭后各景象的核素迁移过程和照射途径,建立各景象核素迁移的概念模型、数学模型,并计算各景象对人类产生的照射剂量。假设核素活度浓度与剂量之间呈线性关系,推导满足剂量准则下各景象各放射性核素的活度浓度上限值,选择最小的上限值,从而确定出低放固体废物各核素活度浓度上限值的量级。