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.
Uranium-238 is the most stable isotope of uranium, with a half-life of about 4.468Ã10 years, roughly the age of the Earth. Uranium-235 has a half-life of about 7.13Ã10 years, and uranium-234 has a half-life of about 2.48Ã10 years.