The maximum dimensions for your carry-on bag are: Length - 24 (61cm) including wheels and handles ; Width - 17 (43cm) Height - 10 (25cm) For additional carry-on items beyond the one-bag limit, each piece will incur a fee. Refer to the checked baggage page for more information.
Tritium (3H) is the most stable radioisotope of hydrogen. That is, of all radioactive isotopes of hydrogen, tritium is the least radioactive. It has a proton and 2 neutrons in its nucleus. Tritium decays through beta minus decay and changes to helium-3. It has a half-life of 12.32 years.
Radioactive elements with a half-life of several hours are generally used. Read more about radiation therapy here. A sample of Uranium atoms has about a 50% chance of undergoing radioactive decay at any time. Within the Uranium-238 decay cycle, half-life can range from billions of years to mere seconds.