That's grossly misleading. The first problem with it, is it assume that coal fired plants release their fly ash up the stocks, they don't, not anymore.
The second problem with it is the radio isotopes are Uranium and Thorium which as far as these things go are a nothing burger. AKA they are very weakly radioactive and they don't bio-accumulate.
Third problem with it is fly ash is about as radio-active as plain dirt. Because dirt also has similar levels of thorium and uranium in it.
At the end of the day, the average person would be more exposed to radioactivity from walking by fly ash (in a pond, in a pile, in the air, wherever it is) than from shielded waste. "[...] fly ash most definitely is not more radioactive than nuclear waste. Instead, I think he is saying that if you stood next to a pile of fly ash you’d probably get a bigger radiation dose than if you stood next to radioactive waste that is adequately shielded." [0]
Also statistics helps frame an accurate picture when looking at it in terms of energy, not mass: "'In fact, the fly ash emitted by a power plant—a by-product from burning coal for electricity—carries into the surrounding environment 100 times more radiation than a nuclear power plant producing the same amount of energy.' Our source for this statistic is Dana Christensen, an associate lab director for energy and engineering at Oak Ridge National Laboratory as well as 1978 paper in Science authored by J. P. McBride and colleagues, also of ORNL." [1]
> the average person would be more exposed to radioactivity from walking by fly ash (in a pond, in a pile, in the air, wherever it is) than from shielded waste.
This is wrong because your shielding is radioactive. Concrete is radio active, dirt is radio active, fly ash is radio active. Your granite counter top is radio active.
Fly ash sitting in a landfill has zero radio-logical hazard. Because there isn't anything about it that will increase the local back ground radiation level. And because the radio-isotopes have a zero risk profile.
That same cannot be said for nuclear waste.
That is why the original statement is grossly misleading. And why it pops up again and again like bad penny.
The second problem with it is the radio isotopes are Uranium and Thorium which as far as these things go are a nothing burger. AKA they are very weakly radioactive and they don't bio-accumulate.
Third problem with it is fly ash is about as radio-active as plain dirt. Because dirt also has similar levels of thorium and uranium in it.