text: Technetium-99ms short half-life of 6 hours makes storage impossible and would make transport very expensive. Instead, its parent nuclide Mo is supplied to hospitals after its extraction from the neutron-irradiated uranium targets and its purification in dedicated processing facilities. It is shipped by specialised radiopharmaceutical companies in the form of technetium-99m generators worldwide or directly distributed to the local market. The generators, colloquially known as moly cows, are devices designed to provide radiation shielding for transport and to minimize the extraction work done at the medical facility. A typical dose rate at 1 metre from the Tc generator is 20-50 μSv/h during transport. These generators output declines with time and must be replaced weekly, since the half-life of Mo is still only 66 hours.
  Molybdenum-99 spontaneously decays to excited states of Tc through beta decay. Over 87% of the decays lead to the  excited state of Tc. A  electron and a  electron antineutrino are emitted in the process (Mo → Tc +  + ). The  electrons are easily shielded for transport, and Tc generators are only minor radiation hazards, mostly due to secondary X-rays produced by the electrons (also known as Bremsstrahlung).
  At the hospital, the Tc that forms through Mo decay is chemically extracted from the technetium-99m generator. Most commercial Mo/Tc generators use column chromatography, in which Mo in the form of water-soluble molybdate, MoO is adsorbed onto acid alumina (AlO). When the Mo decays, it forms pertechnetate TcO, which, because of its single charge, is less tightly bound to the alumina. Pulling normal saline solution through the column of immobilized MoO elutes the soluble TcO, resulting in a saline solution containing the Tc as the dissolved sodium salt of the pertechnetate. One technetium-99m generator, holding only a few micrograms of Mo, can potentially diagnose 10,000 patients because it will be producing Tc strongly for over a week.