It is estimated that between one-half to two-thirds of the value of all U.S. currency in circulation is outside of the U.S. In 1934, the $100,000 Gold Certificate became the highest denomination ever issued. It was never intended for public use. Instead, it was meant solely for official transactions between Federal Reserve Banks.
Enriched uranium. Enriched uranium is a type of uranium in which the percent composition of uranium-235 has been increased through the process of isotope separation. Natural uranium is 99.284% 238U isotope, with 235U only constituting about 0.711% of its weight. 235U is the only nuclide existing in nature that is fissile with thermal neutrons.
Because uranium is radioactive, it is constantly emitting particles and changing into other elements. Uranium has a well-established radioactive decay series. U-238 and U-235 (which has 143 neutrons) are the most common isotopes of uranium. Uranium naturally contains all three isotopes (U-238, U-235 and U-234), and it rarely varies more than 0.01% from the average composition shown in the table below without our intervention. Isotopes of Uranium.