Abstract

Considerable studies have been carried out to evaluate the feasibility of the breed and burn (B&B) concept over the last few decades by applying various simplified or more practical methodologies. In this note, similar studies are performed by improving the simplified methodology used by Kumar and Singh in “A Study of Transverse Buckling Effect on the Characteristics of Nuclides Burnup Wave in a Fast Neutron Multiplying Media,” [Journal of Nuclear Engineering and Radiation Sciience, Vol. 5, p. 4 (2019)] and in other international studies. A consistent parametric approach is adopted for the study on buildup and propagation of a nuclear fuel burnup wave in a fast neutron multiplying medium for two-dimensional cylindrical geometry with azimuthal symmetry. The Multiphysics finite element computational code COMSOL is utilized to solve coupled multigroup neutron diffusion and burnup equations in the U-Pu cycle. The characteristics of the wave are evaluated in terms of transient time (TT) and transient length (TL); TT and TL represent the time and distance covered by the wave in establishing a sustained fuel burnup wave, respectively. The steady-state space is characterized by wave velocity and reaction zone width (full-width at half-maximum and full-width at 10% of maximum).

The results of this study are presented in terms of the characteristics of the transient and steady-state parameters to assess the feasibility of a fuel burnup wave. It is concluded that a sustained fuel burnup wave (about 10 years in a reactor of 5-m length) is attainable in application of the B&B concept in traveling wave technology, although optimization of the transient wave parameters (TT of 1100 days and TL of 2.614 m) is necessary to prolong reactor operating life. The results of the present improved model are compared with the results of Kumar and Singh’s simplified model by performing a sensitivity study of the characterization parameters with radius. Variation of TL with respect to radius (decrement of about 10.6% in the modified model and about 5.4% in the simplified one with the increment in reactor radius from 1.1 to 1.3 m) is relatively less compared to the variation observed for TT (decrement of about 76.5% for the modified approach and about 19.1% for the simplified case). The sensitivity of the wave parameters is studied for different values of neutron source strength used in the analysis.

摘要

在过去的几十年里，通过应用各种简化或更实用的方法，已经进行了大量研究来评估繁殖和燃烧 (B&B) 概念的可行性。在本说明中，类似的研究是通过改进 Kumar 和 Singh 在“快中子倍增介质中核素燃耗波特性的横向屈曲效应研究”中使用的简化方法进行的，[核工程与辐射科学杂志，卷。第 5 页。4（2019）]和其他国际研究。采用一致的参数方法研究具有方位对称的二维圆柱几何在快中子倍增介质中核燃料燃耗波的形成和传播。Multiphysics 有限元计算代码 COMSOL 用于求解 U-Pu 循环中的耦合多群中子扩散和燃耗方程。波的特性根据瞬态时间（TT）和瞬态长度（TL）进行评估；TT 和 TL 分别代表波在建立持续燃料燃耗波时所覆盖的时间和距离。稳态空间的特征是波速和反应区宽度（半峰全宽和最大 10% 的全宽）。

这项研究的结果是根据瞬态和稳态参数的特性来评估燃料燃耗波的可行性。得出的结论是，在行波技术中应用 B&B 概念可以获得持续的燃料燃耗波（在 5 米长的反应堆中大约 10 年），尽管优化了瞬态波参数（TT 为 1100 天，TL 为2.614 m) 是延长反应堆运行寿命所必需的。通过对具有半径的表征参数进行敏感性研究，将本改进模型的结果与 Kumar 和 Singh 的简化模型的结果进行比较。TL 相对于半径的变化（在修改模型中减少约 10.6%，在简化模型中减少约 5.4%，反应堆半径从 1.1 增加到 1。3 m) 与观察到的 TT 变化相比相对较小（修改后的方法减少了约 76.5%，简化的情况下减少了约 19.1%）。针对分析中使用的不同中子源强度值，研究了波参数的敏感性。