What unit of length used in nuclear physics is named after a famed Manhattan Project scientist?

The unit of length in question is the fentometre, also called a fermi.

The Royal Society of London elected Fermi as a Foreign Member in 1950. The Enrico Fermi Award, given to scientists for achievement in energy, was established in his honor; he was its first recipient in 1954. The synthetic element fermium was named for him in 1955. Also, the Fermi National Accelerator Laboratory, a particle-physics research laboratory near Chicago, is named for him.

https://en.wikipedia.org/wiki/Femtometre
https://en.wikipedia.org/wiki/Enrico_Fermi

A fermi (aka femtometer) is the unit of length equal to 10 E^-15, or one-quadrillionth of a meter.

www.aqua-calc.com/what-is/length/fermi