By measuring concentrations of stable isotopes in bomb debris, researchers have worked out the details of a nuclear test performed 70 years ago.

Scientists have long debated the efficiency and yield of the first atomic bomb, called Trinity, which was detonated in 1945 in New Mexico. Susan Hanson and her colleagues at the Los Alamos National Laboratory in New Mexico analysed bomb debris and measured changes in both the isotope ratios and the total levels of molybdenum — a stable decay product of zirconium isotopes, which form as a result of nuclear detonation and are short-lived. The team then calculated the original concentrations of the zirconium isotopes and came up with a yield for the Trinity detonation that was in line with that officially reported.

This approach could prove useful in ongoing nuclear non-proliferation and verification efforts, the authors say.

Proc. Natl Acad. Sci. USA http://doi.org/bmjk (2016)