The Magic of Uranium

 So this is an Idea from a Lindybeige video. What would be the rules of a world where magic existed. 

Lindy suggests Wizards having to physically touch bonfires to cast firebolt spells. Or using flywheels ands steam to power there spells. I came up with a similar idea

Imagine a universe where uranium oxide Which has been known about since Roman times, is used to fuel magic. So you can use Uranium oxide to colour glass. Imagine then a wizard having to wear 1000's of beads  to power his spell. Once the spell is cast the beads are depleted 

Or people stirring pitchblende to get the powder for yellow cake and use it in amulets for protection

It works fine against the spells, but still makes you sick. 

Now imagine the conditions of processing this in a hi medieval fantasy universe