You are correct in all respects. Alpha particles are easily stopped by a
few centimeters of air and/or the skin. Of the three forms of "radiation"
emitted by uranium and its decay products, alpha particles are usually ignored
because they are easily absorbed as I mentioned. Beta particles are not
so easily absorbed and neither are gamma rays. However, when uranium compounds
are ingested or absorbed into the body, alpha particles become very dangerous
because they are now absorbed by internal body tissue and they are very
ionizing due to their charge and hence produce tissue distruction. If you
breath these compunds into your lungs, they tend to stay there because they are
composed of heavy elements. If you ingest them they tend to concentrate in the
liver like all toxic substances.
As I mentioned before these compunds in solution can be absorbed through
your skin. If you are using them in a glaze, you should wear gloves. Once
the ceramic has been fired, they represent little or no danger.
Uranium compounds were once used fairly extensively in pottery and glass.
Some old pots, plates and glassware are fairly radioactive i.e. you can
measure the radiation with a GM survey meter.
Bob Schramm