In the massively popular first-person shooter game Destiny 2, whose new “Season of the Chosen” event begins today, it’s revealed that long-dead bad guy Clovis Bray I built a lab that has survived the apocalypse-like Collapse. Basically, everything in the world has fallen into ruin, but centuries after its construction, Bray’s lab is still humming—and the active nuclear reactor inside is rigged to self-destruct if anyone intrudes.

Bray’s notes within the game indicate he built a fission reactor, which “requires less frequent refueling than a fusion plant,” and is “easy to hide something in the design that will allow it to achieve, ah, extremely prompt criticality.”

Yes, nuclear energy can last very long, but what’s the limit? Could a human-made system of any kind, like an advanced nuclear reactor, last at least hundreds of years—the lowest fandom guesstimate between Bray’s lifetime and the relative present in Destiny 2—without any sentient supervision?

Let’s see if we can find out using some math, common sense, and an assist from NASA.

Bray is onto something when he says fission is a better bet for longer-lasting reaction between refuels. Many of today’s small modular reactors or even microreactors rely on designs with very few moving parts at all, some with literally none inside of totally enclosed nuclear “batteries.”

Think of this like a grade-school volcano, where instead of pouring vinegar into the open cone, you enclose it next to the baking soda and then shake the container up.

In this case, an enclosed battery could be its own downfall. It means very little access for any kind of refueling. A more open style of reactor could be refueled, but these usually require workers and technical support, lasting only about a nail-biting week without human help.

How could we get around this requirement?

Easy: automation. While the nuclear fuel part of the process can’t be ignored, we can try to rig solar-powered support for it. In fact, the blueprint is there in Bray’s fictional diary. Consider the passage in which he discovers aliens in the Destiny universe have figured out how to extend the life of their star, a de facto fusion reactor:

“They had refueled the star. They were stoking it. Enormous portals dumped streams of hydrogen into the giant, replenishing its mass and fusion power.”
For some amount of time, a solar- or wind-powered mining operation could dig up and refine nuclear fuel to replenish the reactor.

Fission is still more sensible for those of us who can’t harvest a star yet, because fusion uses an enormous amount of energy that would be hard for even the most efficient renewables to manage. Fusion could maybe work if the population in question could plug the reactor in before they took off, but today’s idea of fusion technology is still very finicky—and we won’t have a maintenance crew to get it back online, let alone a fresh infusion of enormous power.

So a fission plant with the right setup of renewables-powered refueling could, as the saying goes, last as long as the sum of its parts. There are ways to make systems redundant, so that one wayward cog wouldn’t take down the whole assembly. But still ... could the reactor really last for centuries?

For some clues, let’s look to space.

NASA launched the Jupiter- and Saturn-bound Voyager 1 and 2 space probes in 1977, and researchers recently heard back from Voyager 2 after a long, worrying silence. But the secret to 43 years and counting of Voyager, or NASA's GOES-3 satellite that operated for 38 years, is probably in how little energy these devices use. Voyager and many satellites already use radioisotope thermoelectric generators (RTGs). These self-contained nuclear batteries model how a closed power system can work for decades.

Each Voyager spacecraft has three power sources called multi-hundred watt RTGs, which are running at far less today than their initial 158-watt output. Technically, though, these are still nuclear-powered devices that almost fit our brief.

With enough RTGs, especially if you could automate and renewably power the manufacture of replacement RTGs, you could put together a Bray-like device to self-destruct your evil plans in near perpetuity. When satellites or spacecrafts fail, it’s usually a moving part or a collision that causes the damage.

So, while the spectacular meltdown that threatens players in Destiny 2’s Deep Stone Crypt raid is unlikely without the excellent “magical science” that threads through the game, you could certainly do some damage with an aging, but functional RTG. Imagine making exactly the right mechanical design so that a delicate thread is severed in an emergency, causing two components of an explosion to collide.

This, too, is a loose idea from real life. The upcoming generation of fission reactors uses physics in the form of temperature-expanding materials, for example, to ease operation to a halt instead of triggering a meltdown. The reactors use gravity to aid with cooling mechanics or prevent traditional meltdown scenarios.

And while the reactors aren’t looking to do Bray-style misadventures, it’s easy to see why the stable, decades-old RTG that powers Voyager 1 and 2 is a role model for the next generation of nuclear here on Earth.