Improvement of Geant4 Neutron-HP package: Unresolved resonance region description with probability tables

IF 1.9 3区工程技术 Q1 NUCLEAR SCIENCE & TECHNOLOGY

Annals of Nuclear Energy Pub Date : 2024-09-24 DOI:10.1016/j.anucene.2024.110914

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引用次数: 0

Abstract

Whether for shielding applications or for criticality safety studies, solving the neutron transport equation with good accuracy requires to take into account the resonant structure of cross sections in part of the Unresolved Resonance Region (URR). In this energy range even if the resonances can no longer be resolved experimentally, neglecting them can lead to significant numerical biases, namely in flux-based quantities. In Geant4, low energy neutrons are transported using evaluated nuclear data libraries handled by the Neutron High-Precision (Neutron-HP) package. In the version 11.01.p02 of the code, the URR can only be described by average smooth cross sections that do not take into account the statistical resonant structure of the cross sections. To overcome this shortcoming, the treatment of the URR with the use of the probability table method has been implemented in Geant4 and successfully validated with the reference Monte Carlo neutron transport codes MCNP6 (version 6.2) and Tripoli-4® (version 12). These developments will be taken into account in the next release of Geant4. All the validations of Geant4 have been performed with probability tables generated from both the NJOY and CALENDF pre-processing tools. Therefore Geant4 now has this unique feature to study the relative impact of the strategies involved during the production of probability table by the two pre-processing codes. This has been used to show that self-shielding is important also for inelastic cross sections in the example of ²³⁸U. The tool to generate probability tables usable by Geant4 either from NJOY or from CALENDF is made available on a dedicated GitLab repository and will be included in Geant4.

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改进 Geant4 中子 HP 软件包：用概率表描述未解决的共振区域

无论是在屏蔽应用还是临界安全研究中，要准确求解中子输运方程，都需要考虑未解析共振区（URR）部分截面的共振结构。在这一能量范围内，即使共振无法再通过实验得到解决，忽略共振也会导致显著的数值偏差，即基于通量的数值偏差。在 Geant4 中，低能中子是通过中子高精度（Neutron-HP）软件包处理的已评估核数据库传输的。在 11.01.p02 版本的代码中，URR 只能通过平均平滑截面来描述，并没有考虑到截面的统计共振结构。为了克服这一缺陷，Geant4 中采用了概率表法处理 URR，并成功地与参考蒙特卡罗中子输运代码 MCNP6（6.2 版）和 Tripoli-4®（12 版）进行了验证。Geant4 的下一个版本将考虑这些进展。Geant4 的所有验证都是通过 NJOY 和 CALENDF 预处理工具生成的概率表进行的。因此，Geant4 现在具备了这一独特功能，可以研究两种预处理代码在生成概率表过程中所涉及的策略的相对影响。以 238U 为例，研究表明自屏蔽对非弹性截面也很重要。从 NJOY 或 CALENDF 生成 Geant4 可用的概率表的工具已在专门的 GitLab 存储库中提供，并将包含在 Geant4 中。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Annals of Nuclear Energy 工程技术-核科学技术

CiteScore

4.30

自引率

21.10%

发文量

632

审稿时长

7.3 months

期刊介绍： Annals of Nuclear Energy provides an international medium for the communication of original research, ideas and developments in all areas of the field of nuclear energy science and technology. Its scope embraces nuclear fuel reserves, fuel cycles and cost, materials, processing, system and component technology (fission only), design and optimization, direct conversion of nuclear energy sources, environmental control, reactor physics, heat transfer and fluid dynamics, structural analysis, fuel management, future developments, nuclear fuel and safety, nuclear aerosol, neutron physics, computer technology (both software and hardware), risk assessment, radioactive waste disposal and reactor thermal hydraulics. Papers submitted to Annals need to demonstrate a clear link to nuclear power generation/nuclear engineering. Papers which deal with pure nuclear physics, pure health physics, imaging, or attenuation and shielding properties of concretes and various geological materials are not within the scope of the journal. Also, papers that deal with policy or economics are not within the scope of the journal.