Just close down the place leave absolutely no markings outside. Probability that somebody will just start digging in some random place is quite low. Also the w

Just close down the place leave absolutely no markings outside. Probability that somebody will just start digging in some random place is quite low. Also the waste is stored several hundred meters deep and all the tunnels will be filled. This means accessing the waste later will require significant effort and reasonably advanced technology (which means those doing the digging would likely be aware of radiation).