Effect of neutron fluence on the safety of the RPV of the VVER 1200

IF 2.1 3区工程技术 Q1 NUCLEAR SCIENCE & TECHNOLOGY

Nuclear Engineering and Design Pub Date : 2025-09-22 DOI:10.1016/j.nucengdes.2025.114478

K M Rakib Al Hasan , Md.Imtiaj Hossain , Md.Shafiqul Islam

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引用次数: 0

Abstract

The Reactor Pressure Vessel (RPV) is the most critical safety component in a nuclear power plant (NPP), especially in light-water reactor (LWR) designs. It is subjected to continuous neutron irradiation, extreme coolant pressure, and temperature during normal operation. Neutron irradiation of the RPV degrades its mechanical properties, highlighting the necessity of accurately predicting embrittlement phenomena to prevent brittle failure. Although the RPV of VVER-1200 is manufactured using advanced steel grades that have been developed and optimized through decades of experience with earlier VVER designs, such as the VVER-230 and VVER-440, it has a short operational history. As a result, there is still limited long-term surveillance data. Therefore, continued research and modeling are essential to reliably predict the RPV’s lifetime and ensure its structural integrity under extended service conditions. This work offers a unique investigation by combining the full-core neutronic behavior of the VVER-1200 and its impact on the RPV lifetime using OpenMC simulation. In this study, a VVER-1200 full core model is created to evaluate the fast neutron flux (>0.5 MeV) spectrum . The analysis reveals a maximum fast neutron fluence of 4.11 × 10¹⁹ neutrons/cm² over 60 years of operation, resulting in a ductile to brittle transition temperature (DBTT) shift of about 68 °C for the RPV base metal and 69 °C for the weld metal, impacting RPV safety and longevity. Burnup analysis shows an initial k_eff > 1.2 with fresh fuel, decreasing as fissile isotopes deplete over time. After 60 years operation, the displacement per atom (DPA) reaches 0.021, with the base metal’s fracture toughness (

K_{I C})

decreasing to 85 MPa√m and the weld metal dropping from 136 MPa√m to 87 MPa√m. The DBTT shift is also influenced by impurity concentrations, with Cu at 0.30 %, Ni at 1.3 %, and P at 0.020 % showing the most significant shifts under the same neutron fluence. The results can be used for aging management of the RPV of a VVER-1200.

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中子通量对vver1200反应堆RPV安全性的影响

反应堆压力容器（RPV）是核电站（NPP）中最关键的安全部件，特别是在轻水反应堆（LWR）设计中。在正常运行期间，它受到连续的中子辐照、极端的冷却剂压力和温度。中子辐照会降低RPV的力学性能，这突出了准确预测脆化现象以防止脆性破坏的必要性。尽管VVER-1200的RPV是使用先进的钢种制造的，这些钢种是通过数十年的早期VVER设计（如VVER-230和VVER-440）的经验开发和优化的，但它的运行历史很短。因此，长期监测数据仍然有限。因此，持续的研究和建模对于可靠地预测RPV的使用寿命并确保其在延长使用条件下的结构完整性至关重要。这项工作提供了一个独特的研究，结合了VVER-1200的全核中子行为及其对使用OpenMC模拟的RPV寿命的影响。本研究建立了一个VVER-1200全芯模型来评估快中子通量（>0.5 MeV）谱。分析表明，在60年的运行过程中，快中子的最大通量为4.11 × 1019中子/cm2，导致RPV母材的延性到脆性转变温度（DBTT）变化约68°C，焊接金属的DBTT变化约69°C，影响了RPV的安全性和寿命。燃耗分析显示，使用新燃料时的初始燃耗系数为1.2，随着时间的推移，随着可裂变同位素的消耗而降低。运行60年后，每原子位移（DPA）达到0.021，母材断裂韧性（KIC）降至85 MPa√m，焊缝金属断裂韧性从136 MPa√m降至87 MPa√m。DBTT位移也受杂质浓度的影响，在相同中子通量下，Cu为0.30%，Ni为1.3%，P为0.020%时的位移最为显著。研究结果可用于VVER-1200型RPV的老化管理。

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.