https://www.cnet.com/news/fukushima-ice-wall-prevents-leaking-of-radioactive-water/

But the visible recovery is undermined by the invisible; a still highly radioactive land and groundwater that continues to mix with the radioactive water of the destroyed reactors at Fukushima Daiichi.

One solution attempting to mitigate the ongoing water contamination is the Ice Wall, a super-cooler refrigerant being piped 100 feet underground, freezing the ground solid and stopping the flow of fresh water towards the sea.