If that's what you mean, then say "coal ash ponds emit more radiation than can be measured outside spent fuel cooling pools".
"Coal ash is more radioactive than nuclear (power) waste" is a completely difference factual statement and is untrue by many orders of magnitude.
Or better yet, walk around an operating nuke plant with a radiation detector and then do the same walk around an operating coal plant. I am willing to bet the coal plant will spike higher.