Nuclear reactor full-core deterministic computational schemes in transport theory

我们的重点是第三代和第四代反应堆运行模拟、燃料管理和安全分析所需的全堆芯反应堆物理代码。中子扩散理论目前用于此目的，但参考计算需要一个更准确的传输现象的表示。基于最近的进展有关的MOC和计算机集群的发展，我们现在可以提出一个家庭的严格的全核心解决方案的技术依赖于离散纵坐标方法（规则的几何形状）和MOC（非结构化的几何形状）的实施。我们建议开发的MOC是基于以下内容的原创性贡献： 1.线性来源假设散射和裂变源沿沿着每个轨道段交叉点线性变化 域。采用抛物阶菱形差分格式，得到了各层的通量矩 音量.目前大多数的实现都是基于平坦源近似和阶跃特性 差异 2.散射各向异性在MOC解的基础上，我们提出了一种变阶Legendre算法， 散射各向异性的扩展模型。 3.合成加速度MOC已经实现在DRAGON 4代码使用二阶代数崩溃（AC）的方法限于扁平源和各向同性散射加速。我们建议用一阶AC方法代替二阶AC方法，并将其散射表示推广到高阶。 4.平行性我们建议使用Fortran-2008 ISO标准的一个名为“coarray”的功能来实现一个 适用于MOC和AC方法的并行求解技术。龙4 主运行中心的实施目前尚未并行。使用Unified Portable C（UPC）是另一种选择 用C语言编写的算法的完全并行求解技术。

We are focusing on full-core reactor physics codes required for simulation of operation, fuel management and safety analyses of third- and fourth-generation reactors. Neutron diffusion theory is currently used for this purpose, but reference calculations require a more accurate representation of transport phenomena. Based on recent advances related to the MOC and to the evolution of computer clusters, we can now propose the implementation of a family of rigorous full-core solution technique relying on the discrete ordinates method (for regular geometries) and on the MOC (for unstructured geometries). The MOC we propose to develop is an original contribution based on: 1. linear sources. Scattering and fission sources are assumed to vary linearly along each track segment crossing the domain. A parabolic order diamond differencing scheme is used to obtain the flux moments in each volume. Most current implementations are based on flat sources approximation and step-characteristic differencing. 2. scattering anisotropy. With the MOC solution, we propose to implement a variable-order Legendre expansion model for scattering anisotropy. 3. synthetic acceleration. The MOC already implemented in DRAGON4 code is accelerated using a second-order algebraic collapsing (AC) method limited to flat sources and isotropic scattering. We propose to replace the second-order AC method with a first-order AC method and to generalize its scattering representation to higher orders. 4. parallelism. We propose to use a capability of Fortran-2008 ISO standard named "coarray" to implement a massively-parallel solution technique adapted to the MOC and to the AC method. The DRAGON4 implementation of the MOC is currently not parallelized. Using the Unified Portable C (UPC) is an alternative massively-parallel solution technique for algorithms written in C language.