全陶瓷微密封燃料有效多群截面计算方法研究

全陶瓷微密封（FCM）燃料是一种弥散颗粒燃料。由于弥散颗粒燃料存在双重非均匀性，传统的确定论方法及蒙特卡罗方法皆难以处理这种双重非均匀效应以获得有效多群截面。本文基于超细群方法建立FCM燃料的有效多群截面计算方法。为描述燃料棒内TRISO颗粒的非均匀性，在共振能量段，通过采用超细群方法求解包含TRISO颗粒的一维球模型得到超细群缺陷因子，通过超细群缺陷因子修正所有核素的超细群截面即可将颗粒和基质均匀化。由于TRISO颗粒在热能区也存在较强的自屏效应，在热能区，利用穿透概率及碰撞概率等价得到多群缺陷因子，通过多群缺陷因子修正所有核素的多群截面将燃料和基质均匀化。均匀化后的FCM燃料组件即可视为普通压水堆燃料组件进行共振计算。利用丹可夫修正因子等价得到FCM燃料组件各燃料棒的等效一维棒模型，对一维棒模型求解超细群慢化方程从而得到共振能量段的有效自屏截面。数值结果表明，该方法能有效处理FCM燃料的双重非均匀性，得到精确的有效自屏截面。

Multi-group Effective Cross Section Calculation Method for Fully Ceramic Micro-encapsulated Fuel

Fully ceramic micro-encapsulated (FCM) fuel is a type of dispersed particle fuels. Due to the double heterogeneity of dispersed particle fuels, the traditional deterministic method and Monte Carlo method are difficult to be applied to it. In order to overcome this problem, the multi-group effective cross section calculation method for FCM fuel was proposed. To describe the heterogeneity of TRISO particles, the hyperfine group disadvantage factors were calculated by solving a one-dimensional model of the TRISO particle with hyperfine group method in resonance energy range. The matrix and TRISO particles will be homogenized by correcting the hyperfine group cross section with hyperfine group disadvantage factors. Due to the strong self-shielding in thermal energy range, multi-group disadvantage factors were calculated by penetrating probability and collision probability equivalent, and then the matrix and TRISO particles were homogenized by correcting the multi-group cross section with multi-group disadvantage factors. The FCM fuel is able to be calculated as traditional PWR fuel after homogenized. The one-dimensional model of every fuel rod in fuel assembly will be got by Dancoff correction factor equivalent. And then the hyperfine group calculation is carried out based on the one-dimensional rod model to get the effective cross section in resonance energy range. The numerous numerical results show that the proposed method can deal with the double heterogeneity of FCM fuel and get precise effective self-shielding cross section.