[Timwi]

Antineutrinos are produced in nuclear reactors when the radioactive products of nuclear fission undergo beta decay.

Source: https://physics.aps.org/articles/v10/66

[TheSpiceIsLife]

Ah, right.

This publication[1] says neutrinos, but the article it references says antineutrinos[2].

That explains my misunderstanding.

1 https://www.energy.gov/science/np/articles/detecting-neutrin...

2. https://www.osti.gov/pages/biblio/1959810-evidence-antineutr...