Actions such as thermal degradation, mechanical breakage and the like exist in the steam explosion process.

在蒸汽爆碎过程中存在热降解和机械断裂等作用。

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Furthermore, it would take a combination of extreme events to make things dangerous in Tokyo (nuclear re-criticality, steam explosion) etc all of which are being rendered less and less likely as time passes and the heat decay process progresses.

FORBES: Fukushima Cleanup Recap