Onkalo in Finland is a repository being built 5km underground designed to store high-level nuclear waste for 100,000 years. This channel 4 documentary provides a thoughtful look at the construction of something that must last longer and remain safe for far longer than human history to-date.

Underground it must survive wars, being forgotten, the collapse of civilisation and even potential ice-ages. And do so without maintenance or records being kept. It’s a very tall order, a hundred millennia is an inconceivable time-frame. Consider that we don’t completely understand, say, the pyramids built a mere 5 millennia ago. Will future humans be able to read any inscriptions or correctly understand that the repository is a very dangerous place? With so much of the far future unpredictable the design attempts to account for all conceivable circumstances with, it must be said, considerable diligence. The film is in a wonderful artful style that makes the frequent talking heads interesting. Philosophical musings such as suggesting the repository may pass into legend, a fabled underground vault of immense wealth, gets you thinking about the concept of a distant unknown future very effectively. The film claims 250,000 tonnes of waste worldwide. My own view is that it is idiotic to produce even more such waste when you haven’t figured out how to permanently dispose of the waste you’ve already got. And with terrorism do we really need even more nuclear waste floating around?