The U.S. Energy Dept. is storing at least 820 million kg of nuclear & non-nuclear materials in inventory at 44 sites in 19 states: spent nuclear fuel, plutonium, natural & enriched uranium, depleted uranium, lithium, sodium, lead, chemicals, weapons components, scrap metal & material. Three materials make up an estimated 95% of the total: depleted uranium, scrap metal, & lithium. Left unattended, much of this material could present environmental, health, or safety risks. Maintaining these materials in a safe condition costs millions of dollars/year.