Radioactive tracer such as a cell or tissue, or as a flow tracer to track fluid flow. Radioactive tracers are also used to determine the location of fractures created by hydraulic fracturing in natural gas production. Radioactive tracers form the basis of a variety of imaging systems, such as, PET scans, SPECT scans and technetium scans. Radiocarbon dating uses the naturally occurring carbon-14 isotope as an isotopic label. Isotopes of a chemical element differ only in the mass number. For example, the isotopes of hydrogen can be written as H, H and H, with the mass number at top left. When the
Tritium radioluminescence region of the body, again due to the low penetration depth. The biological half-life of tritium—the time it takes for half of an ingested dose to be expelled from the body—is low, at only 12 days. Tritium excretion can be accelerated further by increasing water intake to 3–4 liters/day. Direct, short-term exposure to small amounts of tritium is mostly harmless. If a tritium tube breaks, one should leave the area and allow the gas to diffuse into the air. Tritium exists naturally in the environment, but in very small quantities. Because tritium is used in boosted fission weapons and thermonuclear