keff behaviour of a potential PWR assembly loaded disposal canister in simplified corrosion scenarios

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

Nuclear Engineering and Design Pub Date : 2025-03-27 DOI:10.1016/j.nucengdes.2025.114007

M. Frankl , L. Berry , A. Vasiliev , D. Rochman , H. Ferroukhi , N. Diomidis , M. Wittel

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Abstract

The Swiss National Cooperative for the Disposal of Radioactive Waste (Nagra) and the Center for Nuclear Engineering and Sciences at the Paul Scherrer Institute (PSI) are investigating how potential long-term changes to the geometry and material composition of the current final disposal canister (BE-ELB) design may affect the neutron multiplication factor (k_eff) of a canister loaded with PWR spent nuclear fuel assemblies (FAs). Several conservative corrosion scenarios were formulated, modeled, simulated and analyzed using the Monte-Carlo codes MCNP6.2® and Serpent2.2. The corrosion-induced effects, such as the replacement of moderator by magnetite, differ significantly from typical fuel lattice configurations used in reactor or storage pool safety analyses. This paper therefore focuses on underlying physical phenomena causing the observed k_eff changes, including analyses of neutron currents and spectra, the ‘6-factor formula’, and the sensitivity of k_eff to specific regions, materials, and nuclides. These analyses showed the canister wall and the corrosion product magnetite to act as a heavy reflector, enhancing the backscattering of neutrons in the epithermal and fast energy ranges. Furthermore, the critical role of the water distribution in all the potential scenarios was revealed. Water inside the FAs clearly increases reactivity by moderation, water outside the remainders of the steel basket, however, has an inhibiting effect on neutron multiplication. All simulation results heavily depend on the specific preliminary ELB design. To that end, the results of this study can help to optimize the ELB design and the Swiss concept for the final disposal of high-level radioactive waste.

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简化腐蚀情况下潜在压水堆组件装载处置罐的keff行为

瑞士国家放射性废物处理合作组织（Nagra）和Paul Scherrer研究所（PSI）的核工程与科学中心正在研究当前最终处置罐（BE-ELB）设计的几何形状和材料组成的潜在长期变化如何影响装载压水堆乏核燃料组件（FAs）的罐的中子增殖系数（keff）。使用蒙特卡罗代码MCNP6.2®和Serpent2.2制定，建模，模拟和分析了几种保守腐蚀场景。腐蚀引起的影响，如用磁铁矿代替慢化剂，与反应堆或储存池安全分析中使用的典型燃料晶格结构有很大不同。因此，本文的重点是引起观测到的keff变化的潜在物理现象，包括中子电流和光谱的分析，“6因子公式”，以及keff对特定区域、材料和核素的敏感性。这些分析表明，罐壁和腐蚀产物磁铁矿充当了一个重反射器，增强了中子在超低温和快速能量范围内的后向散射。此外，还揭示了水分布在所有可能情景中的关键作用。FAs内的水通过适度的作用明显地提高了反应性，然而，钢篮残余物外的水对中子增殖有抑制作用。所有仿真结果在很大程度上取决于具体的ELB初步设计。为此目的，这项研究的结果可以帮助优化ELB设计和瑞士高放射性废物最终处置的概念。

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

Nuclear Engineering and Design 工程技术-核科学技术

CiteScore

3.40

自引率

11.80%

发文量

377

审稿时长

5 months

期刊介绍： Nuclear Engineering and Design covers the wide range of disciplines involved in the engineering, design, safety and construction of nuclear fission reactors. The Editors welcome papers both on applied and innovative aspects and developments in nuclear science and technology. Fundamentals of Reactor Design include: • Thermal-Hydraulics and Core Physics • Safety Analysis, Risk Assessment (PSA) • Structural and Mechanical Engineering • Materials Science • Fuel Behavior and Design • Structural Plant Design • Engineering of Reactor Components • Experiments Aspects beyond fundamentals of Reactor Design covered: • Accident Mitigation Measures • Reactor Control Systems • Licensing Issues • Safeguard Engineering • Economy of Plants • Reprocessing / Waste Disposal • Applications of Nuclear Energy • Maintenance • Decommissioning Papers on new reactor ideas and developments (Generation IV reactors) such as inherently safe modular HTRs, High Performance LWRs/HWRs and LMFBs/GFR will be considered; Actinide Burners, Accelerator Driven Systems, Energy Amplifiers and other special designs of power and research reactors and their applications are also encouraged.