It turns out that nuclear waste has more in common with the financial world than being a metaphor for the worst of its toxic assets. Nuclear waste - some of which remains disastrously radioactive for 100,000 years - turns out to be the ultimate tail risk. Tail risk, of course, is the statistical term much in vogue in the financial press for describing unlikely events. (The 'tail' in tail risk refers to the tail-shaped edges in the bell curve of a normal distribution.) These allegedly unlikely events are sometimes referred to as black swans. Black swans are occurring with such regularity in these volatile times that they can no longer be considered true statistical outliers. [Take] a look at these outlier events within the context of building nuclear waste containment vessels. Repository builders have to take into account a tail risk of future humans disturbing the site and not realising the danger facing themselves and their ecology. People might regress towards a pre-industrial state or lose language over a timescale like that. So you have to design a marker that scares people away, but doesn't flip them over into morbid curiosity towards exploring further and, potentially, dooming an entire civilisation with radioactive poisoning.