冬夏海阳核电厂核素在近海域的迁移路径和浓度分布研究

为制定核电厂发生核泄漏事故应急响应预案,需要快速预测事故后放射性核素在近岸的迁移路径和浓度分布。本文首先根据实时气象数据,基于拉格朗日方法和欧拉方法,建立了核电厂近海域核素扩散模型,并验证了该模型的可靠性;其次,用该模型对比分析了夏季和冬季海阳核电厂核素的迁移路径和浓度分布。分析结果表明,夏季受东南风和洋流的影响,海阳核电厂核素主要沿着海岸线向东迁移;冬季受西北风和洋流的影响,核素首先沿着海岸线向东迁移,然后快速向东南迁移;无论冬季还是夏季,5 d后核电厂近海域核素浓度比释放总量降低约9个数量级,10 d后核素浓度比释放总量降低约10个数量级。      

福岛核污水排放预测计算研究

通过建立太平洋水动力模型,计算得到福岛核泄漏发生后,相关海域核素的扩散规律、福岛核污水船运排放预测及距离海岸1 km隧道核污水排放预测情况。通过计算结果与实际测量值进行对比发现,模拟结果与实测值吻合良好,证明了计算结果的准确性。计算结果表明：核污水一方面随着海流迁移,另一方面扩散,放射性核素浓度较高区域沿海岸线向北迁移,随后向东北方向螺旋前进。核污水船运排放后核素随海流迁移较慢,基本呈现以排污点为中心的轴向扩散,核污水中放射性核素受海流、潮流和扩散的影响,逐渐呈现带状分布,且向东北方向迁移,并于第15日左右到达日本沿海地区。无论是沿海,还是1 km排放,放射性核素会很快扩散到沿岸。随着扩散的进行,核污水中放射性核素受海流、潮流和扩散的影响,逐渐呈现带状分布,且向东北方向迁移。     

滨海核电厂液态流出物间歇排放数值模拟分析

应用非结构化网格MIKE 21水动力模型及对流扩散模块,针对某滨海核电厂工程海域建立液态流出物排放数学模型,对核电厂运营期间液态流出物中核素在等浓度排放条件下4种不同典型潮时(涨憩、落急、落憩、涨急)起始的间歇排放进行数值模拟,并与连续排放进行比较,给出了不同工况下液态流出物在环境水域中全潮平均相对浓度分布及影响范围、不同半径海域内核素的平均相对浓度以及取水相对浓度特征值。对比分析显示,滨海核电液态流出物在受纳水体中的输移、扩散主要受潮流影响。落急时刻起始的间歇排放方式总体上在环境影响和取水浓度方面均具有显著优势。计算结果可为核电厂液态流出物排放方式的优化及海洋环境影响评价提供了依据。     

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。      

中尺度海域核设施低放废液排放方案的初步探究

以某海域为例,初步探究某核设施正常运行时低放废液在中尺度海域的排放方案。采用MIKE21模拟软件,利用水动力模块(HD)和对流扩散模块(AD)建立了中尺度海域放射性核素迁移扩散数值模型,以半衰期为12.5年的放射性核素氚为例,考虑了排放口离岸距离、排放口方位和不利风向等因素,对放射性核素在中尺度海域的迁移分布状况进行了数值模拟。初步计算结果表明,排放口设在某河口东北侧,距岸不小于30 km的海域,有利于放射性核素的迁移、扩散。     

JRODOS模拟核事故时核素扩散及剂量时空分布

核事故时核素扩散范围和造成的辐射剂量是核电厂事故应急措施制定的重要参考,利用JRODOS软件模拟了不同气象源和大气扩散模型对核电厂核素浓度和辐射剂量时空分布的影响。结果表明:WRF气象场情景下核素的扩散范围广,FNL气象场情景下核素浓度和有效剂量区域均值较高。不同大气扩散模型中LASAT模型模拟的有效剂量最高。这为核事故后果评价数据来源和大气扩散模型选择提供了依据。     

花岗岩近表层^134Cs活度直接测量

核素在岩石裂隙中迁移时，一方面随裂隙水对流弥散，另一方面吸附在岩石裂隙表面并向岩石中扩散。因此，除了测量裂隙出口端流出液浓度外，还需测定裂隙近表层的放射性活度分布。文章描述了岩石裂隙近表层１３４Ｃｓ活度直接测量装置和测量方法，并给出１３４Ｃｓ在花岗岩裂隙近表层活度分布测量结果。     

不同排放深度下温升作用对核电厂液态流出物近区稀释的影响研究

针对国内某典型内陆核电厂,基于一种三维水动力混合区模型及决策支持系统CORMIX(即康奈尔混合区专家系统),对核电厂液态流出物水底、水中淹没式排放及高于水面排放等排放情景共4种排放深度下,温排水温升作用对核电厂排出的液态流出物的近区稀释扩散能力的影响分别进行数值模拟。计算结果表明:温升对核电厂液态流出物近区稀释效果的影响规律主要依赖于流出物的排放深度;水底淹没式排放或水体中下层排放时,温升作用有利于液态流出物的近区稀释,水体中上层排放和高于水面排放时,温升作用对流出物近区稀释扩散能力产生明显的不利影响。     

基于MIKE21的滨海核设施液态流出物稀释扩散规律及排放优化的模拟研究

本文针对滨海核设施液态流出物海域排放问题,利用水动力软件M IK E21建立了排放海域的水动力和稀释扩散模型,模拟了液态流出物的放射性核素在潮汐作用下的稀释扩散规律,研究了潮型、潮位、排放时段等因素对放射性核素稀释扩散效果的影响.模拟研究发现,在潮差较大的落潮时段集中排放放射性核素,近岸放射性核素的浓度更低,更有利于液...     

海岛下垫面对核事故核素扩散影响规律研究

为研究核事故发生后气载核素在海洋环境中的扩散,以海岛核电厂为研究对象,采用计算流体动力学（CFD）模拟的方法对海岛核电厂各下垫面要素、风速变化、喷口速度变化进行了模拟,并用风洞实验验证CFD模拟的准确性。结果表明,山体会对地面最大扩散因子产生显著影响;平台的高度增加时,地面最大扩散因子降低,出现距离更靠近喷口;风速的增大会使得面最大扩散因子出现位置后移;喷口速度增大会使得地面最大扩散因子变小,其出现位置后移;在喷口速度变化的情况下,地面最大扩散因子的CFD模拟值和高斯烟羽模型计算值呈倍数关系,并以此对高斯烟羽模型进行了修正。      

Method for Using Measurements of the Contamination of Bottom Deposits to Estimate the Source of Radioactive Substances Flowing into a River

A method of estimating the strength of a stationary source of radioactive substances entering a river is proposed. The method is based on statistically reliable measurements of the concentration of radionuclides in bottom deposits. The stationary model of the transport of a radioactive impurity in a two-dimensionally uniform flow is used to determine a relation between the concentration of radionuclides in bottom deposits and the strength of the source. The model is based on the two-dimensional equation for turbulent diffusion and takes account of the interaction of radioactive substances between the water mass (solution, suspension) and bottom deposits. The source of ⁶⁰Co entering the Don River with contaminated underground waters as a result of an incident, which occurred in 1985, in a storage site for liquid wastes from the Novovoronezh nuclear power plant is examined as an example. The average yearly inflow of the radionuclide is estimated to be ∼1·10¹⁰ Bq/yr, which is several times less than the estimates made by experts. __________ Translated from Atomnaya Energiya, Vol. 99, No. 3, pp. 221–228, September, 2005.     

Calculation of risk-based detection limits for radionuclides in the liquid effluents from Korean nuclear power plants

In order to review if present detection limits of radionuclides in liquid effluent from nuclear power plants are effective enough to warrant compliance with regulatory discharge limits, a risk-based approach is developed to derive a new detection limit for each radionuclide based on radiological criteria. Equations and adjustment factors are also proposed to discriminate the validity of the detection limits for multiple radionuclides in the liquid effluent with or without consideration of the nuclide composition. From case studies to three nuclear power plants in Korea with actual operation data from 2006 to 2015, the present detection limits have turned out to be effective for Hanul Unit 1 but may not be sensitive enough for Kori Unit 1 (8 out of 14 radionuclides) and Wolsong Unit 1 (9 out of 42 radionuclides). However, it is shown that the present detection limits for the latter two nuclear power plants can be justified, if credit is given to the radionuclide composition. Otherwise, consideration should be given to adjustment of the present detection limits. The risk-based approach of this study can be used to determine the validity of established detection limits of a specific nuclear power plant.     

Development of a short-term emergency assessment system of the marine environmental radioactivity around Japan*

The Japan Atomic Energy Agency (JAEA) has, for many years, been developing a radionuclide dispersion model for the ocean, and has validated the model through application in many sea areas using oceanic flow fields calculated by the oceanic circulation model. The Fukushima Dai-ichi Nuclear Power Station accident caused marine pollution by artificial radioactive materials to the North Pacific, especially to coastal waters northeast of mainland Japan. In order to investigate the migration of radionuclides in the ocean caused by this severe accident, studies using marine dispersion simulations have been carried out by JAEA. Based on these as well as the previous studies, JAEA has developed the Short-Term Emergency Assessment system of Marine Environmental Radioactivity (STEAMER) to immediately predict the radionuclide concentration around Japan in case of a nuclear accident. Coupling the STEAMER with the emergency atmospheric dispersion prediction system, such as Worldwide version of System for Prediction of Environmental Emergency Dose Information version II (WSPEEDI-II), enables comprehensive environmental pollution prediction both in air and the ocean.     

Simulation of Radionuclide Migration and Diffusion in Yangtze River Delta

A two-dimensional numerical model was selected for the proposed inland nuclear power plant in this paper. The two-dimensional hydrodynamic model of the Yangtze River estuary was constructed based on the MIKE model. The flow field of receiving water and the diffusion of radioactive liquid effluent in the Yangtze River delta under a hypothetical accident were simulated. The detention time, process and extent of radioactive contamination in the Yangtze River delta under tidal action were evaluated. The simulation results show that it could basically reflect the actual situation of receiving water. Tidal action will increase the detention time of nuclides in delta waters, but it will also bring radionuclides to the outer sea, and the nuclide concentration will gradually decrease.     

放射性核素在长江三角洲的迁移扩散模拟

本文针对拟建的内陆核电站,选择二维数值模拟,基于MIKE模型构建长江河口二维水动力模型,模拟了受纳水体的流场及假想事故情况下放射性液态流出物在长江三角洲的稀释扩散情况。本文评估了在潮汐作用的影响下,核事故污染物在长江三角洲的滞留时间、影响过程和影响程度。模拟结果显示：模拟的流场基本能反映受纳水域实际情况,潮汐作用会增加核素在三角洲水域的滞留时间,但同时也会将放射性核素带向外海,核素浓度会逐渐降低。     

某拟建滨海核电厂址大气扩散规律初探

本文介绍了在我国东部沿海某拟建核电厂址进行的大气扩散试验的概况和主要结果,包括现场试验和风洞模拟实验。现场试验主要有：百米气象铁塔四个高度整年风、温逐时观测;地面风场、海陆风及热内边界层的观测与分析;SF6示踪试验与湍流测量等。在现场试验基础上尝试提出了计算滨海核电厂址年均大气扩散因子的模型。该模型既考虑了向岸流与离岸流的区别,又考虑了混合层与热内边界层、混合释放与扩散参数随陆距变化等综合影响因素。     

Handling of the Bottom Residues of a Nuclear Power Plant

The following technological operations are suggested for reprocessing bottom residues from nuclear power plants: separation of radionuclides using oxidation, filtration, and selective absorption, solidification and long-term storage of secondary radioactive wastes (cement compound from filtration stage and spent sorbent in filters); concentration and obtaining dry salts from bottom residues from which radionuclides have been removed. Laboratory and stand tests have been performed, showing that radionuclides can be removed from the bottom residues of nuclear power plants to a level below the ASA_sat according to NRB-96. This treatment decreases the volume of radioactive wastes by approximately a factor of 100. The dried purified bottom residues, which are commercial danger class III wastes, are shipped to storage sites used for industrial wastes. Calculations of the material flows are performed and the site arrangement of the wastes is given for the bottom residues from the Kursk nuclear power plant. 1 figure, 2 tables, 12 references.