Improvement of computer code DRAGON5 for providing support to safety assessment, criticality studies and core simulation of nuclear reactors

中子学确定性模拟基于两个软件组件，一个专用于单元燃料组件，另一个专用于整个堆芯。更复杂的一种是基于中子玻尔兹曼方程解和特定模型的晶格代码。它通过为完整的堆芯模拟代码提供多参数数据库，用于临界安全和反应堆物理应用。在过去的30年里，蒙特利尔理工学院（École Polytechnique de Montréal，简称EMPT）开发了晶格代码DRAGON（目前为第5版）和三维扩散代码DONJON（用于全堆芯模拟）。这两个代码在开放源代码许可下在世界各地广泛分发，并被许多大学和组织使用，他们正在成为DRAGON/DONJON的专家用户。玻尔兹曼方程求解算法的数值性能对DRAGON的精度和CPU效率都有很大的影响。该NSERC/DG计划的短期目标是研究与现代格型代码中使用的基本数值技术相关的数学基础、精度和加速问题，以提高DRAGON V5的整体性能。长期目标是向核工业提供软件工具和计算方案，使它们能够评估现有和新型核反应堆的性能和安全特性。前两个子项目的重点是Boltzmann方程的确定性求解技术：（1）发展离散纵标（SN）方法和间断Galerkin（DG）格式;（2）改进特征线法（MOC）和发展一阶代数折叠（FOAC）方法。为了开发和验证基于DRAGON V5最新进展的计算方案，定义了另外三个子项目：（3）压水堆两级计算格式的发展（4）ASTRID两层计算格式的发展（用于工业示范的先进钠技术反应堆）晶格，（5）为ASTRID型全堆芯模拟开发微耗尽能力。与玻尔兹曼方程的求解技术的发展或改进有关的主题显然是博士学位。水平CLE-2000语言的一级和二级计算方案的开发及其与燃耗相关的蒙特卡罗模拟的代码到代码验证是工程硕士学生的水平。这三个工程硕士子项目将与IRSN和GRS等工业合作伙伴密切合作，继续关注生产应用。

Neutronics deterministic simulations are based on two software components, one dedicated to the unit fuel assembly and the other dedicated to the full core. The more complex one is the lattice code based on a solution of the Boltzmann equation for neutrons and on specific models. It is used for criticality safety and for reactor physics applications by feeding the full core simulation code with a multi-parameter database. In the last 30 years, École Polytechnique de Montréal (EPM) has developed the lattice code DRAGON, now at Version 5, and a 3D diffusion code named DONJON for full core simulations. These two codes are widely distributed across the world under an open-source license and are used by many universities and organizations who are becoming expert users of DRAGON/DONJON.***The numerical performance of the solution algorithms for the Boltzmann equation has a strong effect on both the accuracy and the CPU-effectiveness of DRAGON. The short-term objective of this NSERC/DG program is to study the mathematical foundations, accuracy and acceleration issues related to the basic numerical technique used in modern lattice code, in a way to improve the overall performances of DRAGON V5. The long-term objective is to provide software tools and computational schemes to the nuclear industry that will enable them to assess the performance and safety characteristics of existing and new types of nuclear reactors. The first two sub-projects focus on deterministic solution techniques of the Boltzmann equation: (1) Development of a discrete ordinates (SN) method with a Discontinuous Galerkin (DG) scheme; (2) Improve the method of characteristics (MOC) and develop the first-order algebraic collapsing (FOAC) method. Three more sub-projects are defined in order to develop and validate computational schemes based on the most recent advances available in DRAGON V5: (3) Development of two-level computational schemes for PWR (pressurized water reactor) lattices, (4) Development of two-level computational schemes for ASTRID (Advanced Sodium Technological Reactor for Industrial Demonstration) lattices, (5) Development of micro-depletion capabilities for ASTRID-type full-core simulations.***Subjects related to the development or improvement of solution techniques for the Boltzmann equation are clearly of the Ph.D. level. Development of the one- and two-level computational schemes in CLE-2000 language and their code-to-code validation with respect to burnup-dependent Monte Carlo simulations is of the level of M.Eng. students. The three M.Eng. sub-projects will be investigated in close relationship with industrial partners such as IRSN and GRS, keeping our focus on production applications.**