Good questions,
Wish I had some good answers. Here are a couple of websites that might have some info: The Ux Consulting Company and Uranium Info. I haven't delved too deeply in either site.
On the western boarder of Colorado, where the last Uranium boom left its indelible mark, is the town of Grand Junction. It turns out that cement contractors in the 1960's found the tailings of Uranium production attractive as an aggregate in their concrete. Later the EPA eventually paid to remove and replace the concrete made from this material.
Ship's ballast? Of course it is dense as hell, so it'd work great as ballast; but....... sigh.......