"It has been done for hundreds of years" isn't a good argument. There is a reason "Appeal to tradition" is one of the more famous logical fallacies.
Also: The radiation doses used in this trial are very likely much, much higher than what you would get from such a bath in radioactive water (otherwise the water would be so radioactive that staying in there or even drinking it would kill you very quickly), so this doesn't really tell us anything about whether the traditional modalities do anything or not. And yes, stuff like that also exists in Austria with Radon caves, and many other places.