GAO undertook a review to determine the relationship between commercial spent nuclear fuel reprocessing and worldwide weapons proliferation and the adequacy of safeguards technology to detect diversions of weapons-usable material. In 1977, the President decided to indefinitely defer commercial nuclear spent fuel reprocessing in the United States because of the risks of nuclear technology and/or materials being diverted from such plants. This decision was justified on the basis that the United States can sustain its nuclear power program for the foreseeable future without reprocessing and that premature commercialization of reprocessing in the United States could encourage other nations to expand reprocessing activities. Despite the U.S. policy, many other countries continue to expand their reprocessing programs. Reprocessing, the chemical separation of usable uranium and plutonium from spent nuclear power reactor fuel, produces plutonium which can be used to construct a nuclear weapon. Safeguard systems used at federal reprocessing plants cannot assure that diversions of weapons-usable material for unauthorized purposes can be detected in a timely manner. Material control and accountability systems cannot accurately measure and account for weapons-usable material in spent fuel rods and in the process and waste streams. Instruments needed to measure the precise quantity of this material in spent nuclear reactor fuel have not been developed and current accountability systems cannot determine precisely the quantity being processed. Accurate measurements are also lacking in the radioactive waste portions of reprocessing operations. Since material control and accountability systems do not provide timely information on quantities or locations of weapons-usable material, it is doubtful that a diversion could be discovered before the material could be converted into a suitable form for weapons. The Department of Energy (DOE) relies on physical security to ensure the integrity of its material control and accountability systems. While DOE recognizes the limitations of its systems, it has not comprehensively identified these limitations or developed an approach to provide for as much safeguard protection as may be necessary. To date, effective worldwide systems and controls are nonexistent partly because the United States is not fully supporting a proposed international plutonium management and storage regime. U.S. research and development efforts fall short of providing the needed framework to solve reprocessing safeguards problems.