We do this type of work in both Texas and Louisiana. The good is that drillcuttings make an excellent base material - typically 20-30 lbs/cubic foot more dense than any other building material. With that said, the drilling fluid that coats all of these cuttings needs to be green by some definitive standard. Second, even if the fluid is very green, there may be chlorides in the formation that you do not want spread on the ground. Having green fluids are easy to say, difficult to do because it must be as good or better than oil based mud as a drilling fluid, per se. Ours (Binder's) is and we have the ability to wash the chlorides from these cuttings. Another good - the non soluble polymer we add to make the locations is about 10x stronger than the main product used: "soil cement". Soil cement has a little known downside - when exposed to rainwater, the pH of the water rises to over pH 12. Hope this helps.
Not sure about the radioactivity, as we have not encountered it. However, in years past, I did work extensively with uranium recovery (uranyl trisulfate and uranyl tricarbonate). To wash it free from the solids we used a standard mining technique referred to as countercurrent decantation (CCD). This will wash the uranium and/or radium off of the solids, but if I were you, I would want this done to the solids in question in your area. Clearly, we could encapsulate these solids into the high strength structure, but hesitate to suggest it because radium has such a long decay half life. Further, even if it is no higher than it was underground, it is/was underground vs at the surface.
Suggest the wash approach - we have some scientists that ran CCD tests for Kennicott Copper and Lucky Mac Uranium, so could outline a procedure if you get to that point.
Kathi, do not know it but will google it to see what they say.