Verbal agreements are only as good as the paper they are written on. If your friend hasn't paid you for almost a year I wouldn't hold my breath waiting. Just be glad it only cost yo $500 to find out how good a friend they were. It could have cost you thousands of dollars.
Nuclear Materials. Nuclear materials are the key ingredients in nuclear weapons. They include fissile, fussionable and source materials. Fissile materials are those which are composed of atoms that can be split by neutrons in a self-sustaining chain-reaction to release energy, and include plutonium-239 and uranium-235.
In nuclear fission, atoms are split apart, which releases energy. All nuclear power plants use nuclear fission, and most nuclear power plants use uranium atoms. During nuclear fission, a neutron hits a uranium atom and splits it, releasing a large amount of energy in the form of heat and radiation. More neutrons are also released when a uranium atom splits.