Development of advanced leakage models for lattice calculations based on the method of characteristics.

基于特征方法开发用于晶格计算的先进泄漏模型。

• 批准号: RGPIN-2016-06416
• 负责人: Marleau, Guy
• 金额: $ 2.77万
• 依托单位: École Polytechnique de Montréal
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=710281
• 关键词: Development; advanced; leakage; models; lattice

The long-term objectives of this research program are to develop and implement in transport based lattice codes new or improved numerical simulation techniques to make them more precise and efficient tool to analyse neutrons behaviour in nuclear reactor. This implies: developing new computational models to treat more complex systems; programming robust method to accelerate the solution algorithm for large neutron transport problems; and developing computation schemes benefiting from recent advances in computer technology. Most of the development we proposed will be implemented in the code DRAGON we developed at Polytechnique Montreal. This freely distributed software is used in Canada and abroad for the safety analysis of CANDUs as well as in Laboratories and Universities throughout the world for advanced reactor studies. Lattice codes are mainly used to provide spatially homogenized and energy condensed cross sections for finite core calculation software. For currently operating reactors, this implies performing 2D or 3D neutron transport simulations over fully reflected fuel assemblies. However, nuclear reactors are finite which means neutron will escape from the lattices. This is where leakage models are useful because they provide a mean to simulate this effect in a critical lattice in addition to producing a more representative flux distribution to use for fuel burnup and lattice homogenization. Currently, the most advanced heterogeneous leakage method implemented in lattice codes is the simplified heterogeneous B1 model but its use is limited to the collision probability (CP) method in fully reflected symmetric 2D geometries (axially infinite cell). The short-term goal of this research program is to take advantage of the fact that the method of characteristics (MoC) programmed in DRAGON can solve the transport equation for high order angular flux modes to develop the heterogeneous BN leakage model. As a first step we will implement, my students and I, an advanced B1 heterogeneous leakage method in DRAGON using the MoC in fully reflected non-symmetric 2D geometries. For the second step, work will proceed on generalizing the BN method to 3D geometries with mixed boundary conditions (void axially and white reflection radially). Thirdly, we will develop a 3D cyclic tracking procedure so that mirror like reflection boundary conditions can be treated in the 3D transport solution. This will increase substantially the performance of DRAGON for 3D simulations by removing the computational penalties resulting to the presence of small surfaces at external boundaries. Finally we will propose and implement an advanced acceleration techniques for 3-D full core Monte Carlo simulations. This will be based on an iterative algorithm to solve the fine mesh MoC equation with incoming angular flux boundary conditions generated by a coarse mesh Monte Carlo simulation.

该研究计划的长期目标是在基于传输的晶格代码中开发和实施新的或改进的数值模拟技术，使其成为分析核反应堆中中子行为的更精确和有效的工具。这意味着：开发新的计算模型来处理更复杂的系统；编程鲁棒方法来加速大型中子输运问题的求解算法；并开发受益于计算机技术最新进展的计算方案。我们提议的大部分开发将在我们在蒙特利尔理工学院开发的代码 DRAGON 中实现。这种免费分发的软件在加拿大和国外用于 CANDU 的安全分析，并在世界各地的实验室和大学中用于先进的反应堆研究。 格码主要用于为有限核心计算软件提供空间均匀且能量凝聚的截面。对于当前运行的反应堆，这意味着在完全反射的燃料组件上执行 2D 或 3D 中子输运模拟。然而，核反应堆是有限的，这意味着中子将从晶格中逸出。这就是泄漏模型有用的地方，因为除了产生更具代表性的通量分布以用于燃料燃耗和晶格均匀化之外，它们还提供了一种在临界晶格中模拟这种效应的方法。目前，在点阵代码中实现的最先进的异构泄漏方法是简化的异构B1模型，但其使用仅限于完全反映对称二维几何（轴向无限单元）中的碰撞概率（CP）方法。 该研究计划的短期目标是利用 DRAGON 中编程的特征方法 (MoC) 可以求解高阶角通量模式的输运方程来开发异质 BN 泄漏模型。作为第一步，我和我的学生将在 DRAGON 中使用完全反映非对称 2D 几何形状的 MoC 来实现先进的 B1 异构泄漏方法。第二步，将继续将 BN 方法推广到具有混合边界条件（轴向空隙和径向白色反射）的 3D 几何形状。第三，我们将开发 3D 循环跟踪程序，以便可以在 3D 传输解决方案中处理类似镜面的反射边界条件。通过消除因外部边界处存在小表面而导致的计算损失，这将显着提高 DRAGON 的 3D 模拟性能。最后，我们将提出并实施用于 3D 全核心蒙特卡罗模拟的先进加速技术。这将基于迭代算法来求解细网格 MoC 方程，其中输入角通量边界条件由粗网格蒙特卡罗模拟生成。