【摘要】 对3×3-2小组件加深燃耗考验元件进行了金相检验,元件最高燃耗(以金属U计,全文同)为30917MW·d/t。检验结果表明:锆包壳外表面氧化膜剥落较为严重,内表面氧化膜最大厚度为19.46μm;芯块与包壳平均间隙为24.93μm;包壳最大吸氢量达到190μg/g;芯块平均晶粒尺寸约为15.65μm,部分晶粒有所长大,但无柱状晶出现;芯块气孔率约为5.52％,尺寸小于5μm气孔的体积份额约占总气孔度的29.86％。在该燃耗下,元件仍具有一定的安全裕度。更多还原

【Abstract】 The metallographic examination of 3 × 3-2 fuel elements with the maximal burnup of 30 917 MW· d/t is carried out. The results show that the external zirconia of the fuel cladding is extracted seriously, the maximal thickness of the internal zirconia reaches 19. 46 μm; the mean gap between the pellet and the cladding is 24. 93 μm; the maximal picking-up of hydrogen is 190 μg/g; the mean grain size of the pellet is about 15. 65 μm, without the columnar crystals; the percentage of the pore is about 5. 52%, which includes 29. 86% of the pore with dimension less than 5μm. It demonstrates that the fuel element is still safe under this level of burnup.更多还原