功率运行/停堆工况下基于SiC包壳的核燃料元件服役行为分析  

Study on the Performance of Nuclear Fuel Based on SiC Cladding under Operation/Shutdown Conditions

作　　者：卢志威 Lu Zhiwei(China Nuclear Power Technology Research Institute,Shen Zhen,Guang dong 518026,China)

机构地区：[1]中广核研究院有限公司,广东深圳518026

出　　处：《核安全》2024年第5期82-89,共8页Nuclear Safety

摘　　要：日本福岛事故后,进一步提高事故容错能力成为核燃料包壳材料的重点研究方向,SiC复合材料在高温强度、辐照稳定性、抗蠕变、抗氧化、耐磨蚀等方面具有显著优势,在轻水堆事故工况下具备较大的容错潜力,因此,基于SiC复合材料的核燃料解决方案是目前国际核燃料界的一个研究热点。与锆合金不同,SiC在中子场的作用下会产生辐照缺陷,进而导致热导率大幅下降,进一步影响燃料棒的径向温度梯度;此外,还会伴随辐照肿胀的发生,且该辐照肿胀量与温度梯度有关。本文采用自主开发的SiC燃料性能分析程序,在考虑上述辐照效应的基础上,对功率运行/停堆工况下基于SiC复合包壳燃料元件的服役行为特点进行了分析。分析结果表明:在功率运行工况下,SiC复合包壳因辐照损伤致热导率降低,以及辐照肿胀会导致芯块-包壳间隙增大,并延迟芯块-包壳间隙闭合时间,进而会使燃料运行温度增加;在热停堆工况下,相比功率运行工况,包壳内侧的环向拉应力会增加;而冷停堆工况下因为系统压力的减小而导致包壳内外压差增加,叠加辐照肿胀梯度,包壳内侧的环向拉应力会进一步增加;此外,在包壳总壁厚不变的情况下,内侧纤维复合层厚度增加有助于减小单质层的环向拉应力峰值,从而降低包壳失效风险。After the Fukushima accident in Japan,further improving the accident tolerance capability has become the key research direction of nuclear fuel cladding materials.SiC composites have significant advantages in high temperature strength,irradiation stability,creep resistance,oxidation resistance,wear resistance,etc.,and have great accident tolerance potential under light water reactor accident conditions.Therefore,the nuclear fuel solution based on SiC composites is a research hotspot in the international nuclear fuel community.Different from zirconium alloy,SiC will produce irradiation defects under the action of neutron field,which will lead to a significant decrease in thermal conductivity and further affect the radial temperature gradient of fuel rods;In addition,radiation swelling will occur,and the amount of radiation swelling is related to the temperature gradient.In this paper,the self-developed SiC fuel performance analysis program is used to analyze the service behavior of SiC clad fuel system under operation and shutdown conditions.The results show that under normal operating conditions,the decrease of thermal conductivity caused by irradiation damage and closing time of pellet cladding gap,and then increase the fuel operating temperature;Under the hot shutdown condition,compared with the normal operation condition,the hoop tensile stress inside the cladding will increase.Under the cold shutdown condition,the pressure difference inside and outside the cladding increases due to the decrease of the system pressure,and the hoop tensile stress inside the cladding will further increase when the radiation swelling gradient is superimposed.In addition,when the total wall thickness of the cladding remains unchanged,the increase of the thickness of the inner fiber composite layer helps to reduce the peak hoop tensile stress of the monolithic layer,thus reducing the risk of cladding failure.

关 键 词：SIC 停堆 包壳 性能 

分 类 号：TL33[核科学技术—核技术及应用]