This report analyzes the danger and economics of weapon-usable fissile materials from both dismantled nuclear weapons and nuclear-plant spent fuel. It found that there will be more weapon-usable plutonium from spent fuel by the year 2003 than from dismantled nuclear weapons. Another problem is the existence of commercial gas centrifuge and other sensitive enrichment plants in nonnuclear weapon states. The study estimates that thermal recycle is uneconomical until the uranium-bearing yellowcake price rises to $50 to $100/lb U3o8 or 30 to 50 years from now. The corresponding numbers for fast reactors are $140 to $220/lb U3o8 or 50 to 100 years from now. The study recommends the U.S. i) try to initiate a 4-element international program for managing dangerous nuclear technologies in the civilian nuclear fuel cycles worldwide, ii) to ask other countries' help for the purchase of highly enriched uranium from former Soviet republics (FSRs), to purchase FSRs' weapon-grade plutonium.