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。     

小溶解度核素在孔隙介质地下水中迁移数学模型的修正

数值模拟粉末状小溶解度放射性废物在地下水中迁移问题时,如果简单地采用孔隙介质核素迁移基本模型的吸附关系式,可能会出现地下水中核素浓度超过溶解度的现象。本文针对线性可逆吸附模式,在考虑核素溶解度限制的基础上,对一般的数学模型进行了修正。对一个假设的算例进行了模拟,模拟结果验证了修正模型的合理性,即当核素溶解度小而在介质中初始浓度较大时,利用修正模型数值模拟该核素迁移问题,不会出现水中核素浓度超过其溶解度的现象,当核素在介质中初始浓度较小时,修正模型的模拟结果与以往模型的模拟结果是完全一致的。     

小溶解度核素在孔隙介质地下水中迁移数学模型的修正北大核心CSCD

数值模拟粉末状小溶解度放射性废物在地下水中迁移问题时,如果简单地采用孔隙介质核素迁移基本模型的吸附关系式,可能会出现地下水中核素浓度超过溶解度的现象。本文针对线性可逆吸附模式,在考虑核素溶解度限制的基础上,对一般的数学模型进行了修正。对一个假设的算例进行了模拟,模拟结果验证了修正模型的合理性,即当核素溶解度小而在介质中初始浓度较大时,利用修正模型数值模拟该核素迁移问题,不会出现水中核素浓度超过其溶解度的现象,当核素在介质中初始浓度较小时,修正模型的模拟结果与以往模型的模拟结果是完全一致的。     

地下水模型系统GMS在核电厂地下水核素迁移数值模拟中的应用

福岛事故后,核电厂地下水环境影响评价逐渐成为人们关注的焦点。本文针对某内陆核电厂,基于地下水模型系统GMS,对某厂址及其附近区域地下水进行三维数值模拟,并对重要核素H-3、Cs-137和Sr-90在地下水中的迁移行为和影响范围进行预测和评价。结果表明:一旦发生放射性废液泄漏事故,H-3迁移速度较快,会影响厂址及其附近区域地下水,但不会对厂址北部河流造成影响;Cs-137和Sr-90迁移速度缓慢,影响范围仅局限在泄漏点周围100 m范围内,不会造成厂外影响。     

余流对核电厂液态流出物排放的影响分析

本文以工程实例为背景,基于深度平均的平面二维数值模拟方法,对核电厂液态流出物在受纳水体中的输移扩散问题进行计算分析。计算潮位、流速及流向与实测水文测验资料吻合良好,可真实反映工程区域的水动力特性;在流场验证良好的基础上,分析余流变化对核素稀释过程的影响机制。结果表明,随着余流的增大,浓度场的影响范围逐步向余流方向偏移,对工程区浓度分布的影响显著,应在环境影响评价过程中予以关注。本文以工程实例为背景,基于深度平均的平面二维数值模拟方法,对核电厂液态流出物在受纳水体中的输移扩散问题进行计算分析。计算潮位、流速及流向与实测水文测验资料吻合良好,可真实反映工程区域的水动力特性;在流场验证良好的基础上,分析余流变化对核素稀释过程的影响机制。结果表明,随着余流的增大,浓度场的影响范围逐步向余流方向偏移,对工程区浓度分布的影响显著,应在环境影响评价过程中予以关注。     

核电厂液态流出物排放数模计算域分析

针对核电厂液态流出物在受纳水体中的稀释扩散问题, 常采用平面二维数值模拟法进行分析, 计算所得流场往往有水文测验资料进行验证, 但对于半衰期较长的核素, 衰变减少的份额较少, 计算范围的大小对计算结果的影响较大。本文结合工程实例, 选取大小不同的两个计算域, 分别进行数值模拟计算, 并对计算所得流态、浓度场分布、浓度通量以及总量守恒进行分析。结果表明, 在计算能力范围内, 应选取较大的计算域; 在满足计算精度和效率的条件下, 排放口距计算边界宜大于80 km的范围。该结果可供核电厂液态流出物排放选择计算范围时进行参考。     

美国内陆核电厂液态放射性流出物排放环境辐射监测与评估

系统分析了2005—2012年美国38个内陆核电厂液态放射性流出物在受纳水体介质中的活度浓度水平,包括沉积物、地表水、饮用水和水生生物。结果表明,除个别核电厂受纳水体(地表水)中的氚活度浓度较高外,其它受纳水体介质(包括沉积物和鱼类)中来自核电厂排放的放射性物质的活度浓度一般处于正常水平。个别内陆核电厂由于受纳水体环境条件的限制,氚的活度浓度水平偏高,但均低于美国环保署(EPA)规定的饮用水中氚的指导水平。核电厂受纳水体排放放射性核素对公众造成的辐射剂量评估表明,美国内陆核电厂运行因液态放射性流出物排放对公众造成的辐射剂量很小。通过分析美国核管会(NRC)规定的监测探测下限和报告水平的要求和内陆核电厂2005—2012年间监测结果,反映了NRC认可的美国内陆核电厂受纳水体受到核电厂液态放射性流出物排放的影响很小。     

737原地浸出采铀工业性试验基地事故放射性废物释放及对地下水环境的影响

本文介绍原地浸出采铀方法的工艺流程及特点，讨论了我国原地浸出采铀工业性试验基地运行期间可能发生的几种事故及事故工况下放射性废物向环境的释放机制。通过对各类事故的分析，得出本工程的最大可信事故为地震造成的蒸发池废水泄漏事故。利用核素在包气带和饱水带中的迁移模式计算了各核素的峰值浓度分布，估算了事故剂量。最后分析了本采铀方法的推广应用前景     

裂隙场址条件下处置场核素迁移的计算

核素随地下水在裂隙中的迁移与在孔隙中的迁移比较,不论从地下水与岩石的接触过程还是介质对核素的吸附作用来说都有很大不同。本文以国内某基岩裂隙场址低中放射性固体废物处置场为例,运用Ecolego软件对核素在裂隙中的迁移过程进行模拟,深入探讨了计算过程中的模型建立、参数选取等关键问题,并对计算结果进行了分析,得出裂隙对核素迁移影响的结论。     

阳江核电站液态流出物对阳江海域环境影响的计算模拟

本文针对阳江核电站50 km核应急计划区的阳江海域,采用切比雪夫谱方法计算了阳江海域的潮流速度和潮位值,进而采用粒子随机行走模型,模拟计算了阳江核电站正常工况下,液态流出物10 h连续排放后,阳江海域内核素氚的浓度分布。计算结果表明,核素迁移扩散24 d后到达海陵岛附近海域,此时有氚分布的区域常规相对浓度值低于0.005,活度浓度值低于0.70 Bq/L,该值与海陵岛海水氚的监测活度浓度(＜0.97 Bq/L)量级上相符。此结果表明,阳江核电站液态流出物中的核素氚对阳江海域环境无明显影响。     

我国东南沿海城市地下建筑氡浓度分布

为了解东南沿海城市地下建筑氡浓度的分布，用固体核径迹法(SSNTD’s)，分别在春、夏、冬3季对沿海7城市地下建筑室内氡浓度进行调查。结果表明，福州具有最高的平均氡浓度，上海的平均氡浓度最低。季节的变化对地下建筑室内氡浓度有影响，各城市氡浓度平均值夏季最高、冬季最低。各城市夏季氡浓度与该城市的年均值的比值与城市中各测点氡浓度之间的离散度有一定的相关性。夏季地下建筑室内氡浓度高的城市，它的平均氡浓度受某些具有高氡水平测点的影响大。     

Fusion Safety Studies in Russia in 1996

The paper seeks to provide a summary report of observations and results of some Russian fusion safety studies performed in 1996. Release of tritium and helium from neutron irradiated beryllium at relatively high neutron fluences has a burst nature. With the growth of the beryllium temperature-increase rate to 90 K/s, the temperature of tritium burst release decreases from 800 to 450–500°C and for helium decreases from 1200 to 500°C. Characterization of carbon and tungsten dust produced in experiments simulating plasma disruptions revealed that dust particle distribution of sizes for graphites and carbon fiber composites has a bimodal nature with maxima in the range of 0.01–0.03 and 2–4 m for composite UAM and in the range of 0.14–0.18 and 2–4 m for graphite MPG-8. Chemical reactivity of beryllium with air was studied as well. A mathematical model for beryllium weight gain under its chemical interaction with air at temperatures of 700–800°C as a function of beryllium porosity, temperature, and interaction duration was developed.     

Trends in computational intelligence in nuclear engineering

Several changes to the focus of Computational Intelligence in Nuclear Engineering have occurred in the past few years. With earlier activities focusing on the development of condition monitoring and diagnostic techniques for current nuclear power plants, recent activities have focused on the implementation of those methods and the development of methods for next generation plants and space reactors. These advanced techniques are expected to become increasingly important as current generation nuclear power plants have their licenses extended to 60 years and next generation reactors are being designed to operate for extended fuel cycles (up to 25 years), with less operator oversight, and especially for nuclear plants operating in severe environments such as space or ice-bound locations.     

Increase in internal friction in uranium with change in temperature

On the basis of the previously described increase in internal friction in uranium during heating, a semiquantitative evaluation was made of the dependence of increase in internal friction on the rate of heating, frequency and amplitude of vibrations. The results of the calculations agree satisfactorily with data obtained experimentally. A study was made of the effect of the initial state of the specimen on the increase in internal friction at the initial stages of heating.     

Temporal changes in vertical distribution of 137Cs in litter and soils in mixed deciduous forests in Fukushima,Japan

Downward migration of ¹³⁷Cs in soils was studied in three mixed deciduous forests c.a. 40 km northwest of the Fukushima Daiichi Nuclear power plant (FDNPP), Japan. We selected three different types of forest regarding to environmental condition such as slope inclinations and snow coverage conditions at the time of deposition. We examined temporal changes in the vertical distribution of ¹³⁷Cs from litter layers to 10 cm soil depth for two years (2.3 to 4.3 years after the FDNPP accident in 2011). At all three study sites, the ¹³⁷Cs in the litter layer had largely migrated to surface soil by 2013. After 2014, about 80% of the ¹³⁷Cs in forest soils (litter layer to 10 cm soil depth) remained within 0–5 cm soil layer. The vertical distribution had not changed substantially since 2014, suggesting that changes to the downward migration rates of ¹³⁷Cs in soils drastically decreased with time. In addition, small amounts of migrating ¹³⁷Cs could not be detected by the present method because there was a large spatial variation in the distribution of soil ¹³⁷Cs. The results showed similar patterns of soil ¹³⁷Cs distribution among the three study sites although there were differences in the environmental conditions.     

广东省进出口食品中的放射性检验

报道了广东省商检中心放射性检验室开展的广东进出口食品中的放射性检验工作。介绍了检验工作采用仪器的主要性能及应用;给出了分析测量方法和探测下限以及实验的质量保证措施,并给出了检验室测量的广东省几种食品中的放射性含量范围,测量结果与我国食品中放射性活度变化范围大体一致。     

固体核径迹研究进展

介绍最近几年固体核径迹研究取得的主要进展，包括：径迹形成机制和探测方法研究固体核径迹在核物理、高能和相对论重离子核反应，原子物理、空间科学、宇宙射线探测、地学、测氡和核孔膜等领域的应用。     

自噬与鼻咽癌放疗研究进展

自噬对鼻咽癌(Nasopharyngeal carcinoma,NPC)具有抑瘤和促瘤双重作用。自噬在NPC发生、发展及转归中起重要作用:低水平、基础自噬有利于细胞的自我保护与新陈代谢,是NPC放、化疗抵抗的重要因素之一;高水平、过度自噬则可导致自噬性细胞死亡,是基于自噬靶点的NPC治疗基础。自噬剂的研发与应用是实现自噬水平调控的关键环节,自噬抑制剂或自噬诱导剂可增敏NPC放、化疗甚至诱导其自噬性细胞死亡,但其作用机理颇为复杂且迄今尚未完全明了。本文着重综述自噬与NPC放疗研究进展,并探讨自噬作为新靶点的NPC治疗前景,尤其X射线作为自噬剂以诱导NPC发生治疗性的自噬性细胞死亡。     

Tritium concentrations in precipitation in Shanghai

Tritium concentrations in precipitation can be used as a criterion to evaluate the tritium baseline of the environment. The tritium concentration in precipitation in Shanghai during 2014-2015 was determined. Values ranged from 0.68 ± 0.04 to 4.11 ± 0.39 Bq/L, and it showed a decreasing trend compared with historical data; however,the values were slightly higher than the natural background tritium level. Additionally, the tritium concentration shows a seasonal variation: It was higher in autumn and winter and lower in summer and spring. A comparison of concentrations in precipitation in Shanghai and around the Qinshan Nuclear Power Plant reveals no correlation,implying that the nuclear power plant operations may not affect the environment of Shanghai. Thus, the raised tritium concentrations in Shanghai might be due to the effects of monsoons, spring leak, raindrop, or other activities that generate tritium there. Those activities may include chemistry research that uses tritium as a tracer.