Like the first, the fourth and final Nuclear Security Summit (NSS) was held in Washington, with others in Seoul (2012) and The Hague (2014). This article makes six arguments by way of a summary stock-take of nuclear security.
First, the threat of nuclear terrorism is real. With 15,000 nuclear warheads, around 1,400 metric tons of highly enriched uranium (HEU) and 500 tons of separated plutonium held at over 100 sites in more than 30 countries, there is enough nuclear materials to increase the world's stock of nuclear bombs to 10 times their present number.
The risk is threefold. Terrorists could acquire HEU or plutonium, make a nuclear bomb and explode it in a target of their choice. Or they could sabotage a nuclear plant and cause an accident along the lines of the Fukushima meltdown five years ago. Or they could steal radiological material from a hospital or scientific lab, wrap it around conventional explosives, and detonate it in a crowded quarter of an economically key city to create panic and cause massive economic disruption with contamination of buildings that would require weeks of cleanup.