Uranium-234 is an isotope of uranium. In natural uranium and in uranium ore, 234U occurs as an indirect decay product of uranium-238, but it makes up only 0.0055% (55 parts per million) of the raw uranium because its half-life of just 245,500 years is only about 1/18,000 as long as that of 238U. The path of production of 234U via nuclear decay is as follows: 238U nuclei emit an alpha particle to become thorium-234. Next, with a short half-life, a 234Th nucleus emits a beta particle to become protactinium-234. Finally, 234Pa nuclei each emit another beta particle to become 234U nuclei.