The ridiculous thing about all of this is plain topsoil has between 0-4ppm of uranium and thorium. Means fly ash is roughly as radioactive as dirt. However pointedly in modern coal fired plants fly ash it scrubbed[1].
Deal with Uranium and thorium is normal geological processes aren't very efficient at concentrating either. Which means commercially exploitable ores are rare and the element remains widely distributed.
[1] It's a bit more tricky since part of the radioactivity from uranium and thorium is due to decay products, some of which probably escape out the stacks. (See radon).
Deal with Uranium and thorium is normal geological processes aren't very efficient at concentrating either. Which means commercially exploitable ores are rare and the element remains widely distributed.
[1] It's a bit more tricky since part of the radioactivity from uranium and thorium is due to decay products, some of which probably escape out the stacks. (See radon).