Very cool, I think many people don’t realize and it might even be because of the words “spent nuclear fuel.” One would think as I did that means less powerful and less dangerous.
However, spent nuclear fuel is much more powerful and dangerous. Nuclear fuel starts out as lack of better words on the mild side however, as reactions take place, it creates a more powerful dangerous nuclear material called plutonium.
Plutonium has a lifespan of 24,000 years before it becomes harmless.
I’m no genius, but I learned about this in videos and our own government websites. I was looking for a video online that a news organization did with those pools of circulating water to keep the radioactive waste, cool until it’s cool enough to be stored in those concrete tubes or cement slabs.
The plant operator in that news report is incomplete dismay that they are being forced to keep all this dangerous stuff on site. They built these plants with the promise by the federal government there would be a place to send it.
The simplest way to look at radiation is that the longer the half-life, the less dangerous it is. While this doesn't get into the details of the different types of radiation, which themselves have different shielding requirements (
alpha, beta, gamma), like alpha rays being blockable by a piece of paper, the concept is the same. Each decay is what emits the emission, so the fewer the number of decays, the longer the half-life (how long it takes to decay to half its original level) and the lower the radioactivity, and thus the relative danger.
Spent nuclear fuel, right out of the reactor, is full of short lived daughter products from the fission process which are decaying rapidly, and thus producing incredible amounts of dangerous radiation, and subsequently, heat. As these short-lived actinides decay away, the amount of heat generated (decay heat) drops off, as do the cooling requirements.
After a period of time, which is about 300-500 years, the main concern becomes ingestion, which is the same sort of hazard for many other "forever dangerous" chemicals that we also store like cyanide, arsenic, mercury, lead...etc.
Plutonium specifically, is valuable, since it can be extracted and reused. This is what the PUREX process employed in France does, it chemically separates the plutonium (and any remaining U235) from the non-valuable materials, the rest of which is vitrified, while the fissile products are used to produce fresh fuel. There is not a lot of plutonium in SNF. In a CANDU reactor, where the fuel bundles start off with much less U235, the amount of plutonium and other fissile material (U235) recoverable after the fuel has been poisoned-out is so small that it's effectively irretrievable barring more complex salvage processes like fluorine reprocessing. But the cost is still prohibitive.
Regarding the volume of spent fuel currently stored on-site from power reactors (which is quite different from weapons program byproducts and the like), in Ontario, all the spent nuclear fuel created since we operated our first power reactor in the early 1960's to now could easily fit inside a Costco. That's a tiny amount of space relative to the massive amount of electricity that was generated.