A solar flare is just one example of many possible causes. There are plenty of other ones. You didn’t touch on any of the others so let me explain - NASA reports on small satellite missions show that about 40% of satellites experience at least partial mission failure within their lifetime. Studies have shown the leading cause of satellite failure is propulsion systems, responsible for about half of all failures. This is not uncommon at all.

Most altitude ranges in LEO still have debris from decades ago, the exception being below 300km, which is basically still in the atmosphere. Unfortunately, debris strikes have regularly produced debris that are flung into higher orbits, so even collisions between satellites in this range are dangerous.

Edit: I also forgot to mention, the five day estimate (now three days actually) wasn’t for a close-call, it was for a debris-generating event.

Collisions aren’t theoretical, near misses are so common that there’s an entire department at NASA dedicated to detecting them and warning satellite owners to adjust course, I know because we were contacted about a possible collision involving our cubesat. Prior to megaconstellations being deployed if humanity stopped adjusting satellite orbits there would be a collision within a month, now there would be a collision within 5 days. It’s only a matter of time until both satellites on a collision course don’t have the ability to adjust course (engine failure or no propulsion/fuel/comms). In the event of a Carrington-style solar flare there’s a good chance a decent percentage of satellites would be knocked out, making this hypothetical into a reality. Further, we can only currently track objects down to about 10cm, but NASA estimates suggest about 500,000 objects exist between 1-10cm in size in LEO.

It seems to be even higher, several studies suggest it’s closer to 50%:

https://pubs.acs.org/doi/10.1021/acs.est.3c05002

Three different studies predicted emitted tire wear proportions (TWP and TRWP) of total emitted MP [microplastic] loads in the environment (both aquatic and terrestrial) for around 45%. (6,7,52) These calculations were mainly based on global, annual production data and matched the TWP proportions of around 40% in this study. However, since C-PVC was excluded here, a comparison of the percentages is not trivial.

If there’s moisture in the filament it vaporises in the extruder, causing steam bubbles that expand and disrupt the laying down of plastic, usually causing inconsistent extrusion lines (which itself causes poor layer adhesion). Some of the filament may end up being heated in the extruder slightly longer than other bits depending on these steam bubbles, which can cause overheating issues like stringing and oozing, etc…

Not to mention that filament that has absorbed water tends to become more brittle, which can lead to the filament snapping off before reaching the extruder. As a result, a filament’s shelf-life is usually dictated by how quickly it absorbs moisture (and also whether UV from the sun weakens it at all, but that’s a lot easier to manage).

What’s your ambient humidity? It’s usually around 80% here and I can barely get my dryboxes down to 30%

Another poster already mentioned that transuranics and other such byproducts tend to be very dense, so a swimming pool can in fact hold tens of thousands of tons of spent fuel. Also, ‘nuclear waste’ is a generic catch-all term that includes less radioactive material, compared to ‘spent fuel’ which is just the really ‘high-grade’ material.

The part about not needing enrichment is worth discussing, but we do have solutions to that already. There are entire classes of reactors dedicated to not producing weapons byproducts or needing enrichment using the same processes capable of generating weapons-grade material. The reason we see reactors that can make these materials so often is because many of the early reactor designs (many still in use today) were explicitly selected for use by the US government during the early days for their dual-use ability to make plutonium for nuclear weapons. Examples of proliferation-safe designs include molten salts and integral fast reactors, but there’s an engineering experience chicken-and-egg problem - they don’t get built very often because we don’t have experience building them. A new design like this will face the same challenges.

TL;DR: Combining a particle accelerator and a nuclear reactor to turn Uranium-238 into Plutonium-239, which then fissions. The reactor itself is subcritical, so if the proton accelerator turns off then the reaction stops.

The main advantages of the system claim to be ‘increased efficiency of fuel use’ since the uranium doesn’t need to be enriched, the ability to burn long-lived nuclear waste, as well as the system being passively safe.

The first point strikes me as an odd thing to focus on, since all nuclear reactors are already very fuel efficient, and if you want maximum efficiency then breeder reactors exist already, which produce more fissile material than they consume - you can’t get much more efficient than that. Fast breeder reactors are also great for burning up nuclear waste too, but they never really took off because, well, there isn’t actually much nuclear waste to use, precisely because typical reactors are already very efficient: A reactor might consume one ton of fuel per year. You could fit all the spent nuclear fuel humanity has ever used into a single swimming pool. I mustn’t be too critical though - any attempt to close the fuel cycle is good, I just don’t think it’s a really pressing issue. Lastly, being passively safe is cool and all, but almost all new reactor designs are, and attaching a particle accelerator to a nuclear reactor sounds like an expensive way of doing it.

All of that being said, I’m always interested to hear about new reactor designs, so I guess we’ll see how it goes.