Nuclear waste stays harmful for an incredibly long time; the signs at the United States’ Carlsbad disposal facility warn people not to dig or drill there until at least 12 000 AD. This leads to a considerable problem. What if the inhabitants of the 210th century don’t know how to read or speak English? They probably won’t understand what a radiation warning symbol means, either.
That makes it rather difficult to find ways to ensure that these radioactive tombs are never opened. Even if they could understand the warnings, are you sure they’d pay attention? Modern archaeologists frequently disturb the tombs of Egyptian Pharohs, despite warnings of a plethora of hideous curses.
The United States Department of Energy has allotted $1M to figure out some sort of acceptable 10 000 year marker system for their waste burial sites. Slate has a fascinating article on it. An exceprt:
During a 2004 cleanup operation at the Hanford nuclear site in Washington state, personnel digging through a trench uncovered a safe containing a glass bottle. And inside the bottle, white sludge. Tests identifying the substance as a type of plutonium gave way to more tests until, in the Spring of 2009, scientists from the Pacific Northwest National Laboratory revealed what, exactly, the crew had uncovered: A 1944 artifact from the fledgling nuclear weapons program—the oldest existing sample of bomb-grade plutonium from a nuclear reactor, with a half-life of 24,110 years. Although this sexagenarian sludge isn’t dangerous to touch—its particles are too large to penetrate skin—it’s poisonous if swallowed or inhaled and will be for centuries to come. Yet it was housed in a flimsy receptacle that should rightfully contain nothing more toxic than bleach. In the rush of nuclear discovery, the mid-century scientists never paused to consider that a trespasser might happen upon the safe and crack it open.
Since that time, “deep geological disposal” has replaced shallow trenches as our preferred nuclear-waste-storage technique. But another, more abstract problem—raised by the Hanford message in a bottle—remains unsolved: not how to store waste but how to label it. Not what container to use or where to bury it but how to explain the long-term dangers of what’s inside to a trespasser. This seemingly simple conundrum (just use a radiation hazard symbol!) is complicated by the fact that such a trespass would prove lethal if it took place not only in 60 years but in 10,000 or 100,000. China, the planet’s oldest continuous civilization, stretches back, at most, 5,000 years. And the world’s oldest inscribed clay tablets—the earliest examples of written communication—date only from 3,000 or 3,500 B.C. It’s impossible to say what apocalyptic event might separate 21st-century Americans from our 210th-century successors. Successors, mind you, who could live in a vastly more sophisticated society than we do or a vastly more primitive one.