Bit of a scandal back in my ancestral homeland. Seems they just tossed steel barrels into a hunk of salt. As anyone from Ontario will attest, salt and steel leads to rust on cars, road bridges, and barrels. Furthermore, the salt is full of natural fractures that leak water, in and out.
I was never a big fan of salt domes for nuclear waste. That was a big thing a few years ago. The US has one for intermediate nuclear waste. I much prefer fractured rock on faults, like our own hometown solution!