The synthesis of precious metals involves the use of either nuclear reactors or particle accelerators to produce these elements. Precious metals occurring as fission products Ruthenium, rhodium Ruthenium and rhodium are precious metals produced as a small percentage of the fission products from the nuclear fission of uranium. The longest half-lives of the radioisotopes of these elements generated by nuclear fission are 373.59 days for ruthenium and 45 days for rhodium. This makes the extraction of the non-radioactive isotope from spent nuclear fuel possible after a few years of storage, although the extract must be checked for radioactivity from trace quantities of other elements before use. Ruthenium Each kilogram of the fission products of 235U will contain 63.44 grams of ruthenium isotopes with halflives longer than a day. Since a typical used nuclear fuel contains about 3% fission products, one ton of used fuel will contain about 1.9 kg of ruthenium. The 103Ru and 106Ru will render the fission ruthenium very radioactive. If the fission occurs in an instant then the ruthenium thus formed will have an activity due to 103Ru of 109 TBq g−1 and 106Ru of 1.52 TBq g−1. 103Ru has a half-life of about 39 days meaning that within 390 days it will have effectively decayed to the only stable isotope of rhodium, 103Rh, well before any reprocessing is likely to occur. 106Ru has a half-life of about 373 days, meaning that if the fuel is left to cool for 5 years before reprocessing only about 3% of the original quantity will remain; the rest will have decayed. To put the values in the table into perspective, the activity in natural potassium (due to naturally occurring ) is about 30 Bq per gram. Rhodium It is possible to extract rhodium from used nuclear fuel: 1 kg of fission products of 235U contains 13.3 grams of 103Rh. At 3% fission products by weight, one ton of used fuel will contain about 400 grams of rhodium. The longest lived radioisotope of rhodium is 102mRh with a half-life of 2.9 years, while the ground state (102Rh) has a half-life of 207 days. Each kilogram of fission rhodium will contain 6.62 ng of 102Rh and 3.68 ng of 102mRh. As 102Rh decays by beta decay to either 102Ru (80%) (some positron emission will occur) or 102Pd (20%) (some gamma ray photons with about 500 keV are generated) and the excited state