When a very massive, rapidly rotating star runs out of nuclear fuel and undergoes core-collapse, a black hole-accretion disk system may form. In these so-called "failed supernovae," accretion onto the rotating black hole can power a jet of relativistic material out the poles. If this jet is sufficiently powerful to disrupt the in-falling stellar envelope, the system explodes as a "jet-driven supernova" or "collapsar." We discuss the recently revived suggestion that collapsars are a major source of the fusion of heavy elements in the universe. We perform general relativistic neutrino radiation magnetohydrodynamics simulations of collapsar disks and extract nucleosynthetic yields. We show how accurate treatment of neutrino transport in the disk transport and the inclusion in-falling stellar material is required to accurately capture the dynamics. We find that very few heavy elements are produced, providing counter-evidence to the aforementioned suggestion.
