Nuclear energy and space have a closer relationship than we might think. Radioisotope thermoelectric generators are key components in many missions, and for years we've studied the possibility of using thermal rockets or controlled detonations. But what brings us here today is a classic question: Why not use space as the final repository for nuclear waste? Or better yet, why not send it directly to the Sun? The folks at Kurzgesagt offer a very detailed answer, and a striking conclusion: it's a terrible idea.
The first thing we need to understand about "nuclear waste" as a blanket phrase ignores many details, and we need to look closer:
- The 90 percent of waste is low-level, such as clothing and tools that have been lightly contaminated. This material doesn't pose major challenges when it comes to disposal.
- The 7 percent is intermediate-level, and includes all components that have remained very close to a core during its operation. The requirements for its storage multiply, but they're not impossible.
- As for the remaining 3 percent... that's our headache. We're talking about the spent fuel we remove from reactors. Radioactive, hot, and very difficult to handle.
There are 440 reactors in operation around the world (437 according to Wikipedia), producing about 11,000 tons of waste per year. So... why don't we start launching rockets with this nuclear junk?
Nuclear Waste to Space: An Impossible Task?
The Kurzgesagt video teaches us that the first difficulty is economic: sending a kilogram of "anything" to low Earth orbit costs $4,000. The additional cost for a reactor would be $100 million per year ($44 billion if we're talking about 440 facilities), making nuclear energy prohibitive.
Now, let's imagine a world where money isn't a problem. The second difficulty is that we don't have enough rockets. In 2021, there were 135 successful launches, and if all of them carried nuclear waste, the grand total would be... nearly 800 tons. To "process" the 11,000 tons per year, we'd have to multiply the number of rockets by 14.
And it gets worse: this leaves all the waste in low Earth orbit, so we need more rockets, bigger and more expensive, to send it to the Moon. A Saturn V would cost $1.5 billion today (adjusted for inflation), moving only 43.5 tons of waste. Shooting it into the void isn't an option either (even bigger and more expensive rockets), and believe it or not, sending the junk to the Sun presents the same problem. Any rocket would have to cancel its orbital motion in order to fall into the star. Again, "bigger, more expensive".
Finally, rocket launches aren't a perfect science, and probably never will be. As we mentioned earlier, 2021 had 135 successful launches... out of 146. That gives us a 7.53 percent chance of causing a local radioactive catastrophe, or triggering a shower of nuclear waste with devastating consequences. The risk is too great.
