Well, right now the answer is not a lot. As I said, the LLW gets held onto until it’s below background levels and then disposed of like non-radioactive waste, the mid-level stuff gets stored separately and the HLW goes through a few stages such as isolation in cooling ponds, then depending on where in the world it is, possibly undergoing reprocessing to remove useful fuel before being placed in Dry-cask storage until a permanent solution is agreed upon.
Not to channel my inner danish prince but, ay, there’s the rub. No one can ever agree on the solutions proposed to the waste storage “problem”. It’s not an actual problem yet because nuclear waste is so dense and easily stored that it generally stays on the property of the reactor without bothering anyone. Not that people don’t go out of their way to be bothered by it.
Now, Connecticut Yankee operated for only 28 years and was a mere 582 MW so this is a comparatively small amount of waste for a nuclear facility. but still, it comfortably sits on a concrete pad about the size of two tennis courts. I’ve touched on dry cask storage before so I won’t go into depth here. Suffice to say that unless you have a crane there is no way to get into any of those casks, and since the spent fuel is either still sealed in the fuel rods, or vitrified into a glass, there is no danger of water leaching it out of the containers.
Quick aside for those that don’t know. Vitrification is when you take the fission products out of spent nuclear fuel, grind them into a powder, then mix them with things like sand and various other chemical oxides then melt the whole thing into a glass. It seals everything inside a non-water-soluble block that is chemically stable and highly impact resistant. Stash blocks of this stuff inside a dry cask and the civilization of cockroaches will have risen and fallen before there’s any danger of radiation from it.
However, the nuclear industry is not interested or, honestly, allowed to get by with doing the minimum safe practice. So what the most approved of project in the industry for storing waste is, is called the Deep Geological Repository (DGR). You probably know of the most famous planned one, Yucca Mountain. Yup, that huge “boondoggle” that was designed and built by the most knowledgeable people in the fields of radiation safety, geology, and construction… and then shuttered by a bunch of people who think that a 15 minute google search for ‘radiation is bad’ make them more informed than people with literal decades of experience and education.
I don’t mean to sound bitter or aggressive, but it’s the fact that the people that protest these solutions to spent fuel storage are generally financed by people who complain about there not being a permanent solution to the spent nuclear fuel “problem”. And those financing groups earn money from people who either believe that nuclear waste is a giant problem or from groups who have a vested interest in preventing a solution to nuclear waste so as to prevent nuclear from having an objection to it removed. It’s a lovely cycle of hypocrisy and preventing solutions to prolong profitable problems.
Stopping nuclear from storing the HLW properly will not make the spent fuel go away. Shuttering every nuclear plant on the planet will not make the HLW go away, because as the protestors are so fond of saying, even if it is erroneous, “it will be radioactive for millions of years!” As I said in part two, the most effective way to reduce HLW is to use it again and again until there is nothing left but actual waste, then storing that in a single place so we can easily keep track of all of it.
To close this part off I’m going to put up some rapid-fire rebuttals to arguments against DGRs like Yucca mountain:
Q1: What if there is an earthquake?
A: They are sited in large stable rock formations such as under granitic thrust mountains like the Rocky Mountains or in the center of large stable rock masses like the Canadian Shield so there is no chance of earthquakes large enough to damage the facility.
Q2: What if it leaks into the water table or aquifer, and poisons the water?
A: The repositories are dug far beneath the water tables of the local area and care is taken to ensure that there are boundary layers of impermeable rock between the DGR and any potential aquifer. Also, remember what I said about vitrified nuclear waste being insoluble in water? Plus, granite type rock where these DGRs are primarily expected to be located already have generally higher than average levels of uranium and thorium in them because that’s how the geology of granite works out.
Q3: What if terrorists come to steal it?
A: Remember in part 2 of this series how I laid out how to reduce the lifetime of radiation in spent fuel to 300 years or less? At that rate of decay, if they wanted the material to make a bomb, just walking into the storage room would be enough to prevent them from leaving. And once it gets cold enough to actually let someone walk in, it’s not really good for much of that stuff anyways.
Q4: What if there is an accident when transporting waste?
A: This is the only question that I feel actually has any merit to it. But luckily nuclear engineers agree with me so they’ve designed cargo containers for nuclear waste that are even More secure than dry casks. Here are some links to some articles about the containers and some of the rather extreme tests that were done on them for public consumption.
Q4: What if someone tries to blow it up?
A: It’s located under a mountain… basically the most unblowupable location known to man. Just ask NORAD and SG-1