10,000 years, 50,000 years, 100,000 years… figures regularly tossed around to scare people into wanting to prevent nuclear reactors from being built because “what will we do with the waste?”
So let’s dive a little deeper into what High-Level Waste is. Remember from the last article, HLW is the spent fuel bundles that were used in the nuclear reactor. But what does that mean?
Yup, that’s the difference between new fuel and “spent” fuel. 1%. imagine getting worked up enough to stop a bridge project because it was 1% over budget? Or because 1% of people didn’t like how it looked?
And honestly, it’s not even 1%. That small amount of plutonium can also be used to continue to fuel the reactor, that’s called breeding fuel. The problem with “spent” fuel is the 0.6% which is comprised of fission products,
and the Actinides (<0.1%) that should have been in the included in the Pu section. But still, it’s a tiny chunk of a tiny little pellet made up of a mixture of approximately 22-24 different elements and isotopes, some of which are actually Very useful too. These elements are the cause of a significant majority of radiation that is released from “spent” fuel pellets. What makes me so confident in saying that?
Because you can handle a new pellet with your bare hand. It’s barely radioactive at all because of the very long half-lives of U235 and U238. So if we could separate all the fission products out from the useful Uranium and plutonium of the fuel then we could bury them or contain them and let them decay naturally while we pull more and more energy out of the fuel we currently have. I have previously mentioned how long we could run civilization on reprocessed fuels, but the question becomes how much waste will be left after that and how long will it last for?
Well eventually the entire pellet will turn into waste, that’s just how burn-up works, minus some mass that gets turned into energy. Thank you Einstein! What changes is how Quickly we produce that waste. With reprocessing, we get to reuse that ~99.4% of the fuel per cycle. Remember to add in some of the mass of the fuel bundle container due to contamination and neutron transmutation and current estimates state that we would reduce the volume of nuclear waste by up to 60x per cycle.
Now the people who want you to be fearful will say that it’s still radioactive, and technically they are right. In fact, it’s almost identical in how much radiation this new more concentrated waste would emit compared to current spent fuel if they were both removed from a reactor at the same time.
The difference is that they Stop being dangerously radioactive much much faster. Taking natural uranium ore as a baseline shows that by only storing the fission products that have no applicable uses, this nuclear waste will reach background levels in about 250 years. But that’s not specific enough as the chart doesn’t tell us how dangerous uranium ore is. So let’s run some numbers with the help of the WISE uranium calculator. Remember from the last article that a spent fuel bundle from a CANDU reactor weighs approximately 24 kg, so let’s assume that our pile of fission products weighs that much and compare it against 24 kg of ore from MacArthur River Saskatchewan. The highest concentration of uranium in any ore body in the world at about 15.8% on average.
So if you had a 24 kg chunk of that ore and stood 1 meter from it for an entire year you would receive 67.2 mSv of radiation. The generally accepted maximum radiation dose for radiation workers under the LNT model is 50 mSv/year. Under some proposed Threshold or Hormesis models, that could be raised to approximately 100 mSv/yr, which is about 1.5 times more than the dose of walking your pet uranium rock every day for a year. So if that is the level we consider as acceptably safe, let us find where that is on the green curve in the picture above… just a hair over 200 years. But we aren’t going to dump someone in a nuclear material storage site with 24 kg of waste and a year’s worth of food and water, that would be weird.
But isn’t radioactive material supposed to be deadly for thousands of years? Isn’t that why we’ve been building giant underground repositories and then having them shut down before anything can actually be stored in them? If we know that reducing nuclear waste volume and timespan of radiotoxicity is possible why aren’t we doing it?
This is the outcome of fearing something irrationally. Solutions that are proposed are accepted because it will get rid of the problem, but suddenly those solutions are deemed not enough because more fear is drummed up.
Being scared of something you don’t understand is, well, understandable. But maintaining that lack of understanding on purpose because you’re scared is the act of a child. You wouldn’t allow your kid to remain afraid of the dark for their whole life, would you? So why might you be allowing yourself to be influenced by your own fear of the unknown?
Edit: updated thanks to a keen-eyed reader who noticed that I had mixed up current safety standards with proposed emergency standards. Thank you achalhp for keeping me honest and accurate!
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