  Heavy elements produced exclusively through rapid neutron capture (the
'$r$-process') originate from violent cosmic explosions. While neutron star
mergers are the primary candidates, another plausible production site are
'collapsars'---collapsing massive stars that form a black hole with an
accretion disk. Here we show that collapsars are too rare to be the prime
origin of $r$-process elements in the Solar System. By comparing numerical
simulations with the early Solar System abundances of actinides produced
exclusively through the $r$-process, we exclude higher than 20% contribution
from collapsars with 90% confidence. We additionally limit $r$-process ejecta
masses from collapsars to less than 10% of the ejecta mass from neutron star
mergers, about $10^{-2}$M$_\odot$.
