Fiestaware is/was a brand of pottery based dishes that was VERY popular back in the fifties. They used uranium oxides and other uranium compounds in order to get the bright, intense colors that the Fiestaware dishes had in their glazes. The radiation those plates give off is pretty intense. However, the radioactivity wasn't as much of a threat as the chemical toxicty from the uranium and lead which was in the glaze. If an acidic food was eaten off of those plates, there's a good chance that some of the uranium and lead would leech into the food.