THE STRANGEST PRODUCT

catalogue on Earth belongs to the USA’S Isotope Business Office, which manages the sale of atomic isotopes produced at Department of Energy labs around the country. It’s got your calcium, platinum and titanium. Your ytterbium, your strontium-90, and of course uranium-235 and plutonium-239 (responsible for Hiroshima and Nagasaki).

In this catalogue, plutonium-238 is the only-on-one-model-year carburettor from the old car you’ve somehow kept running: useful, unique and discontinued. And the old car is a spacecraft: NASA missions bound beyond the influence of the Sun, where solar power isn’t an option, use radioisotope power systems (RPS) to create electricity from the heat of atomic decay. RPS that use 4,8 kilograms of fuel have powered experiments on the Moon and Mars and launched golden records etched with the essence of human civilisation to the edge of the solar system. They run only on plutonium-238, which is (relatively) cheap, has a suitable half-life, and gets plenty hot. But it was a by-product of Cold War-era nuclear weapon factories, now decommissioned, and by the 2010s there were fewer than ten RPS’ worth remaining for NASA to use. So scientists lobbied the US energy department to start making it again. Tennessee’s Oak Ridge National Laboratory produced a 50-gram sample in late 2015 – the first since 1988. This year, having refined the process, the lab expects 300 grams. The goal? 1,5 kilograms per year.