面向小型堆核应急的近区大气放射性核素扩散与快速剂量计算方法研究

近区大气放射性核素扩散与快速剂量计算方法，是小型模块化反应堆应急计划与响应的核心技术，是发挥小型堆经济性和灵活性的关键。本项目面向近区核素扩散与剂量计算中建筑效应缺乏精细、快速模型的问题开展研究，提高核应急模型在密集建筑区的预测能力。大气扩散方面，本项目旨在对流场和湍流场的建筑效应进行研究，建立分区参数化经验模型，提高流场和湍流场预测能力；并研究建筑区下垫面对放射性核素干湿沉积的影响，提出考虑建筑水平表面和垂直表面的干沉积阻力模型和基于降雨量的建筑表面和城市路面的表面清除系数参数方案，建立干湿沉积参数化方案，提高扩散模型的模拟效果。对于近区剂量计算，本项目基于快速多极子算法提出一种考虑建筑屏蔽效应的快速剂量计算方法，满足核应急对高精度剂量计算的要求。最后，本项目将基于多场景模拟或实测数据，对所建立的风场诊断-大气扩散-剂量计算评估链进行全面验证和参数优化。

Near-field atmospheric radionuclide dispersion and fast dose calculation method is not only the key technology for emergency planning and response of small modular reactors (SMRs), but also critical for the economy and flexibility of SMRs. This project is aimed to solve the problem of the lack of precise and fast models of building effects in the near-field radionuclide dispersion and dose calculation model, improving the prediction of nuclear emergency models in dense building areas. In terms of atmospheric dispersion, this project aims at the building effects on the flow field and turbulence field, establishes a partitioned parameterized model to improve the prediction; and studies the influence of the underlying surface of the building areas on the dry and wet deposition of radionuclides, proposes a dry deposition resistance model considering the horizontal and vertical surfaces of buildings and a rainfall-based surface removal coefficient parameterization schemes for building surfaces and urban pavements, establishes a parameterization scheme for dry and wet deposition to improve the simulation of the dispersion model. For near-field dose calculation, this project proposes a fast dose calculation method considering the shielding effect of buildings based on the fast multipole algorithm to meet the requirements of high-precision dose calculation for nuclear emergency response. Finally, the established combinational framework of wind field diagnosis-atmospheric dispersion-dose calculation will be comprehensively validated and optimized based on multi-scenario simulated and measured data.