What is the source of radiation in an X-ray machine? Uranium?

No, but the radioactivity is there. Through the control cabinet below the transformer to generate high voltage accelerated electrons, high-energy electrons and then hit the anode target (metal plate) to produce the photoelectric effect produces X-rays. This is how X-rays are generated. Although the individual working parts are not radioactive, X-rays themselves are penetrating and can destroy human cells and tissues (especially high-energy rays). That is why the state has a special subsidy for anyone who operates X-ray equipment, as in the case of the lower engaged in using X-ray diffractometers for material analysis. Hospitals use low-energy rays in small doses of irradiation on the human body damage is almost non-existent (and can be recovered in the short term without sequelae). But it does not mean that you can take X-rays for 24 hours. Don't be afraid to take it every day. Especially CT because he is a thorough scan, so the amount of radiation is greater than X-ray. It is recommended to try not to do, especially not to children.