I imagine it steaming in a pile in a dark cave.  Occasional sparks might leap from it like screaming fleas bursting into flames.  Cavemen would avoid that corner of the cave with an annoyed grunt, maybe the odd old caveman would pee on it and then wave his glowing penis around at his cavemates gleefully.

“OG pee on strange pile.  Look how OG’s pee pee GLOW! BEHOLD my glowing penis! BEHOLD!”
His pee would also glow and he would put on peeing light shows at night to the delight of his cavemates.

Once a rat, in quiet desperation decided to nibble on the glowing pile and became a magical glow rat.  The other rats suddenly had a newfound respect for the rat and would step aside when he passed.

A brown bear once decided to scoop up a handful of the strange pile, and became a glow bear.  At once feared and admired, the other bears would watch him from afar as he glowed in the distance and was now easily spotted and tracked.

“Ok, look, THERE he is.  Over there by that pine see him?  He’s brighter than the MOON now!”

Move over MOON!  Glow bear is here!

Thousands of years in the future, advanced aliens might find the pile.  “Look Zeptar!  These dumb ass humans left a pile of depleted URANIUM here in the corner of this cave.  What a moronic species.  Lets go ahead and clean it up for them and jettison the stuff into a volcano or something.  Why didn’t they drop this in a volcano, they seem to have plenty of them.  Maybe that’s not a good idea it might blast the radiation out the top.  Better yet, why make it in the first place.  What savages.  What a savage species.”

“Yes, Penomicon, I feel disgusted.”

An 18th century priest once travelled into the future and tried to bless the pile.  “Bless this unholy pile of depleted Uranium.  May it decay quickly and without delay.  May it remain undiscovered here in this cave and let no man unwittingly step in this pile lest he be afflicted and stricken with illness.  May the ocean never wash it out to sea to harm the innocent fish and other beautiful creatures.  May this unholy pile rot in silence and ward away even the most curious cricket.  While we’re at it, bless those spent plutonium rods cooling in the now highly toxic water in Fukushima.  How this isn’t front page news every day right now is beyond me.  In my time, we’d be making very lengthy scrolls on this subject to be sure.

One day, a drunk caveman sat on the pile thinking it was a surrealist chair.  Of course, his butt glowed after that which was the subject of song and tale for generations.

“Remember ol glow butt?  What a site he was.  We always sent him first in the expeditions so everyone could stay on track, but since he was a sad drunk, he would wander off the path.  One time he led us all into a swamp.  Ultimately he wandered off a cliff and a few of our dumbest men followed him!  We always send the dumbest ones first on expeditions, we call them ‘trail bait’.

“OKAY BLUTHOR!  YOU can take POINT!”

“Really?  Me?  I get to go FIRST?  What an HONOR sir.  THANK YOU sir. THANK YOU!”

If an ancient egyptian scholar stumbled upon the pile, he would instantly know what it was and keep his distance.  He would leave extensive runes to warn others of the perils.  “Stay back!  Do not approach this pile.  Keep your distance!”  “Beware!”  “Warning!”

Sadly, the ancient symbols would be misinterpreted to mean, “Poke this pile with your finger and see what happens!” or “I am a pet rock, take me home for your children to play with”  or “For a good time, insert penis”.

If you listen carefully you can here it weeping.  Weeping for its depleted spent cells.  Sobbing to be whole again and replenished.   Crying out “Why?  Why?  Why?”