Application of Boltzmann Transport Equation solutions to nuclear reactor physics and radiotherapy applications

这项NSERC/DG方案的目的是开放晶格代码Dragon 5，用于描述原子水平上的光子和电子输运。这些进展的预期结果将有利于加拿大的两个重要研究领域：1.提高Dragon 5准确描述核反应堆中伽马加热现象的能力。这一能力极大地提高了Dragon 5作为未来CANDU应用程序的国际标准工具集(IST)网格代码在2030-2060年时间框架中的地位。从长远来看，像坎杜斯这样的全规模核反应堆是减少温室效应和我们对化石燃料依赖的最严肃的选择。核能具有寿命周期温室气体排放量极低、容量系数极高等特点。2.将基于光子-电子耦合玻尔兹曼输运方程(BTE)的模型与专用硬件相结合，可在放射肿瘤学中实现更精确的剂量计算和改进放射治疗计划(RTP)。目前使用的RTP技术都存在一个问题，无论是速度慢还是不准确，这使得它们在临床上的使用不是最理想的。我们计划开发一种结合了速度和精度的新的RTP算法。提供这样一种算法将使患者躺在治疗台上时实时计算剂量成为可能，从而使放射治疗领域发生革命性的变化。要取得这些成果，需要在四个具体的分项目上取得进展：d.1为耦合的机械统计编制一致的原子和核数据将扩大横截面处理能力，以便将与次级电子和光子有关的原子数据处理成多组数据。还会产生其他有趣的量：动量传递截面和停止力。在“龙五”的水平，将计算吸收剂量和能量沉积。D.2基于BTE-BFP的中子-电子-光子耦合模型Dragon 5目前是基于中子BTE的解决方案。电子输运用Boltzmann-Fokker-Plank(BFP)方程来描述，其中粒子散射被假定为高度正向峰值，并且可以用偏微分算符利用泰勒展开技术来近似。D.3燃料单元电池或组件中的伽马传输根据光子BTE的说法，裂变、辐射俘获或放射性衰变产生的能量的一部分由光子传输。在某些情况下，初级光子导致电子的释放和次级光子的产生。D.4BTE-BFP在放射治疗中的确定性解第二个应用领域是放射治疗。RTP中使用了电离辐射。基于BTE-BFP的放射治疗模型由两个描述光子和电子输运的耦合方程组成。使用基于耦合的模型的确定性解，为摄动和灵敏度计算开辟了道路。

The aim of this NSERC/DG proposal is to open the lattice code Dragon5 to the characterization of photon and electron transport at the atomic level. Anticipated outcomes of these developments will benefit to two important research fields in Canada: 1. Improvement of the capability of Dragon5 to accurately represent the gamma heating phenomena in nuclear reactors. This capability greatly improves the position of Dragon5 as the future International Standard Toolset (IST) lattice code for CANDU applications in the 2030-2060 time frame. Full-scale nuclear reactors such as CANDUs represent the most serious option to reduce both greenhouse effect and our dependency on fossil fuels on the long term. Nuclear energy is characterized by extremely low lifetime greenhouse gas emission and very high capacity factor. 2. Combining a photon-electron coupled Boltzmann transport equation (BTE) based model with dedicated hardware leads to more accurate dose calculations and improved radiation treatment planning (RTP) in radio-oncology. RTP technologies currently in use all suffer from one problem, be it slowness or inaccuracy, that makes their use suboptimal in the clinic. We plan to develop a new RTP algorithm that combines speed and accuracy. Making such an algorithm available will revolutionize the field of radiotherapy by making it possible to calculate the dose in real time while the patient is lying on the treatment table. These outcomes require advances on four specific sub-projects: D.1 Producing consistent atomic and nuclear data for coupled mechanical statistics Cross section processing capabilities will be extended so as to process the atomic data related to secondary electrons and photons into multigroup data. Other quantities of interest will be generated: the momentum transfer cross section and the stopping power. At the Dragon5 level, the absorbed dose and energy deposition will be computed. D.2 Neutron-electron-photon coupled BTE-BFP based model Dragon5 is presently based on a solution of the BTE for neutrons. Electron transport is described with the Boltzmann-Fokker-Plank (BFP) equation where the particle scattering is assumed to be highly forward peaked and can be approximated with a partial differential operator using Taylor expansion techniques. D.3 Gamma transport in a fuel unit cell or assembly A fraction of the energy produced by fission, radiative capture or radioactive decay is transported by photons, according to a photonic BTE. In some cases, a primary photon causes the releases of an electron and the production of a secondary photon. D.4 Deterministic solution of the coupled BTE-BFP in radiotherapy The second domain of applications is the radiotherapy. Ionizing radiation is used in RTP. The BTE-BFP based model in radiotherapy consists of two coupled equations to describe photon and electron transport. Using a deterministic solution of the coupled based model open the way to perturbation and sensitivity calculations.