There are two types of leaks of contaminated water at Fukushima Daiichi: uphill and downhill. There have been recent news reports about both types, including a regulator's assessment of INES level 3 for the uphill leaks. But I think it is best to consider the two as completely separate. The downhill leaks occurred around the reactor buildings and the seawall. These were mostly discovered early in the Fukushima emergency in 2011, and the high levels of radiation were suspected to come from the reactors, although the containment path was not clear. These leaks were serious partly because they were highly radioactive, partly because they were very close to the then-unprotected sea, and partly because they occurred in a context of great upheaval on the site as a whole; these were scary leaks because so much was unknown.
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