So far the first barrier, which is the fuel cladding, has apparently failed, because they are detecting cesium.

目前，第一道屏障——燃料包壳，已经明显失去功用，因为专家已经在核电站附近检测到了铯元素。

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Zirconium-base alloys are used primarily as fuel cladding material and other core structure material in water cooled nuclear power reactors.

锆合金主要用作核反应堆燃料元件的包壳材料及其他堆内构件。

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M5 alloy was a new zirconium alloy used in high burn up assembly such as fuel cladding, end plug, guide tube and grid spring and so on.

M 5合金是一种适用于高燃耗组件的新型锆合金，主要用作燃料棒包壳、端塞、导向管和定位格架材料。

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High burnup fuel rods stay hotter longer, emit more radioactivity, and may become brittle, scientists suspect, as the cladding that holds them together endures greater stresses.

FORBES: Fancy New Lids for Nuclear Waste Casks, As Contents Get Hotter