So my husband just randomly thought of these books he read as a kid and you know how when you try to remember something and can't and it drives you nuts? So, I'm trying to help him find the books. He doesn't remember much but I'll list what he told me.
There is an atomic/nuclear incident on Earth, a boy (teenager) uses a magic portal to take people with radiation sickness through the portal to a magical world to rid them of the radiation then brings them back to Earth.
There are two magic swords with diamond shaped tips. The boy creates a new planet with the Goddess of Creation of this magic place.
My husband read them in the early-mid 90's (he thinks they were from the 80's because his friend who lent them to him said his older brother had read them) and he said there were at least 2 books, maybe 3.
He thinks one of the covers was purple and black.
He thinks the boy had a sibling but can't remember if it was a brother or sister.
He believes the magic portal was found via a ring or medallion.