Speaking of which, how about smoke detectors ? There is some noise about their radioactivity (of the radioactive types), but is it really the reason for the more common use of the optic types now ? As far as i understand, each is more sensitive to smoke from different materials
The optical system is more sensitive (when adjusted still without false alarms) to the early, smouldering stage of the fire.
The ionization detectors react only to the products of hot burning flames, so with the most common house fires respond way later.
The difference published in literature is around 15 minutes, which is a lot.
This is the main reason, why fire codes are discouraging from the usage of the ionization systems and really encourage to switch to the optical systems.
Of course, when the disaster starts from a hot, rather clean burning flame, the ionization would be faster, but that type of fires is way less common.
So I would guess the reason for ionization detectors loosing grounds is not that much their radioactivity, but just their performance...