LOCA工况下环形燃料元件内包壳外压屈曲试验研究

Experimental Study on Inner Cladding Buckling under External Pressure of Annular Fuel Element under LOCA

环形燃料一种安全高效的新型核燃料。为对环形燃料元件冷却剂丧失事故(LOCA)下整体受压失效形式的问题进行研究,将环形电加热棒、模拟芯块和试验件组装成试验装置,在空气环境中,以环形电加热棒外加热的方式,对环形燃料元件内包壳进行了外压屈曲试验,并将试验屈曲压力与Bresse-Bryan公式计算结果和特征值屈曲数值模拟分析结果进行了对比分析。结果表明:Bresse-Bryan公式计算结果除以安全系数m=2.5得到的结果高于试验结果而不够保守,试验结果分布于特征值屈曲数值模拟分析结果的1/5~1/3之间。本文结果可为环形燃料元件安全评价及后续工程化提供基础数据。

Annular fuel is a new type nuclear fuel for pressurized water reactor(PWR).An annular fuel element has an external cladding corresponding to external coolant channel and an inner cladding corresponding to inner coolant channel,so the PWR whose core is composed of annular fuels has lower core temperature,less fission gas and higher safety allowance.As a new type nuclear fuel and prior to formal operation in the reactor,it’s necessary to test various performances of annular fuel under loss of coolant accident(LOCA)condition out-of-pile to ensure the safety of reactor core.This paper mainly introduces the experiment results of failure behavior of annular fuel element inner cladding under LOCA,and summarizes the relationship between pressure and temperature when external pressure buckling occurs in the inner cladding,which provides basic data for the safety evaluation and subsequent engineering of annular fuel.The external pressure buckling experiment of the inner cladding of annular fuel element was carried out by means of outer heating of annular electric heating rod in air environment.The results of single rod and the entire results of experiment were analyzed.The experimental buckling pressure was compared with the results calculated by Bresse-Bryan formula and numerical simulation results of eigenvalue buckling.The results show that the calculated results of Bresse-Bryan formula divided by the safety factor m=2.5 are higher than the experimental results and not conservative enough.The experimental results are distributed between 1/5 and 1/3 of the numerical simulation results of eigenvalue buckling.The data obtained from the experiment can be used in the analysis and calculation of annular fuel.