In this paper we shed some light on the safety of unsaturated zone nuclear geological repositories in the long run by examining the effect of physical and chemical processes that take place inside a partially failed nuclear waste container. Our analysis addresses the safety of the proposed nuclear repository at Yucca Mountain, which is intended to store high-level nuclear waste. Our study is independent of the US Department of Energy (DOE) analysis, which involves a number of complex computer codes and assumptions, and relies on the performance of an engineered barrier system. Our safety analysis could be applied in general to any geological repository designed to be in an unsaturated zone, since it is based on the geology, unsaturated zone location, and a key characteristic of the waste, heat production. This analysis shows that the radionuclide release from a partially failed waste container, stored in an unsaturated zone geological repository, is likely to be gradual and long delayed. (C) 2010 Elsevier Ltd. All rights reserved.