The intent of minimizing the impact of the large amount of radioactive material potentially released into the atmosphere in a nuclear event implies preparedness activities. In the early phase and in absence of field observations, countermeasures would largely rely on a previous characterization of the transport and dispersion of radioactive particles and the potential levels of radioactive contamination. This study presents a methodology to estimate the atmospheric transport, dispersion and ground deposition patterns of radioactive particles. The methodology starts identifying the main airflow directions by means of the air mass trajectories calculated by the HYSPLIT model, and, secondly, the dispersion and the ground deposition characteristics associated with each airflow pattern by running the RIMPUFF atmospheric dispersion model. From the basis of these results, different products can be obtained, such as the most probable transport direction, spatial probability distribution of deposition and the geographical probability distribution of deposition above certain predefined threshold. The method is trained on the HYSPLIT trajectories and RIMPUFF simulations during five consecutive years (2012-2016) at the Almaraz Nuclear Power Plant, in Spain. 3644 forward air mass trajectories were calculated (at 00 and 12 UTC, and with duration of 36 h). Eight airflow patterns were identified, and within each pattern, the persistent days, i.e. those days in which trajectories at 00 and 12 UTC grouped into the same airflow pattern, were extracted to simulate the atmospheric dispersion and ground deposition following a hypothetical ISLOCA accident sequence of 35 h. In total, 833 simulations were carried out, in which ground contamination was estimated at cell level on a non-homogeneous geographical grid spacing up to 800 km from Almaraz. The corresponding outcomes show a large variability in the area covered and in deposition values between airflow patterns, which provide comprehensive and oriented information and resources to decision makers to emergency management.

中文翻译：

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放射性物质根据气流模式的扩散和地面沉积，以增强对N / R紧急事件的防范能力。

尽量减少核事件中可能释放到大气中的大量放射性物质的影响意味着准备活动。在早期阶段，在没有实地观察的情况下，对策将主要依靠放射性粒子的运输和扩散以及放射性污染的潜在水平的先前表征。这项研究提出了一种方法来估算放射性粒子在大气中的迁移，扩散和地面沉积模式。该方法开始通过由HYSPLIT模型计算出的空气质量轨迹识别主要气流方向，其次，通过运行RIMPUFF大气弥散模型，确定与每种气流模式相关的弥散和地面沉积特征。根据这些结果，可以获得不同的乘积，例如最可能的传输方向，沉积的空间概率分布以及特定预定义阈值以上的沉积的地理概率分布。连续五年（2012年至2016年）在西班牙的Almaraz核电厂对HYSPLIT轨迹和RIMPUFF模拟进行了方法训练。计算了3644个前进空气质量轨迹（在世界标准时间00和12，持续时间为36小时）。确定了八种气流模式，在每种模式下，持续的天数，即将00和12 UTC的轨迹归为同一气流模式的那几天，按照假设的ISLOCA事故序列，模拟了大气扩散和地面沉积。 35小时 总共，进行了833次模拟，其中在距Almaraz最多800 km的非均匀地理网格上，在单元水平上估计了地面污染。相应的结果表明，气流模式之间的覆盖面积和沉积值存在很大差异，这为决策者进行应急管理提供了全面而针对性的信息和资源。