Abstract: An apparatus and method for monitoring stored material is disclosed. Material to be stored and monitored is placed within the innermost container of a series of nested containers and monitoring fluids are circulated in a closed loop of fluid flow through the spaces between the nested containers. Monitoring devices are used to analyze said monitoring fluids to detect leakage of the stored material from the innermost nested container and to detect the migration of external fluids into the series of nested containers. A computer based monitoring system continually checks the values of various parameters of the monitoring fluids to immediately detect and report the presence of stored material or external fluid in the monitoring fluids. The stored material may then be immediately retrieved from storage to repair leaks in the series of nested containers. The invention is particularly suited for monitoring the storage of hazardous material such as radioactive waste material.