The contents of Drum 68660, which investigators said was responsible for the release of contaminants leading to the shutdown of the Waste Isolation Pilot Plant.
LANL drum was root of WIPP accident

Drum 68660, shipped to the Waste Isolation Pilot Plant in Carlsbad from Los Alamos National Laboratory was where all the trouble started.
The Technical Assessment Team (TAT) 277-page report was released Thursday afternoon by the Department of Energy. The TAT’s mission was to find out the root cause of the problems that led to the breach of a waste drum at WIPP, which released radioactive fumes that sickened 21 workers in February 2014.
The TAT’s overarching conclusion was that “chemically incompatible contents of Drum 68660 from Los Alamos National Laboratory in combination with physical conditions (e.g., the configuration of the materials in the drum) supported exothermic chemical reactions leading to a thermal runaway)….”
Thermal and pressure effects resulted in the movement of material during the release event.
Drum 68660, as far as TAT could determine, was the sole cause of the release. According to the report, the thermal runaway was internal in that drum and not cause by outside phenomena.
According to the report’s fact sheet, Drum 68660 breached as a result of internal chemical reactions.