A process and system for conditioning a bulk container for ultra-high purity liquefied gas. Vapor is generated in the container from a conditioning quantity of the ultra-high purity liquefied gas by imposing a temperature difference on the container so that the vapor condenses when a temperature difference is achieved. The resulting liquid reflux, e.g., the condensed liquid drips or flows back to the conditioning quantity of the liquified gas, washes or removes contaminants, e.g., particles, metal and moisture, from the interior surface of the container. A portion of the vapor is vented from the container for reclamation. The used conditioning liquid may also be reclaimed.