Tritium is the common name for hydrogen-3 (3H), which is a radioactive isotope of hydrogen. Like ordinary hydrogen (1H or hydrogen-1, called protium) and deuterium (2H or hydrogen-2), tritium has a single proton in its nucleus. Unlike ordinary hydrogen, deuterium and tritium have neutrons in their nucleus. Deuterium has one neutron in its nucleus and is stable, while tritium's nucleus contains two neutrons and is unstable. Tritium decays spontaneously to helium-3 (3He) through ejection of a beta particle (essentially a high-energy electron). The half-life of tritium is about 12.32 years. Since the number of protons determines chemical bonding, tritium behaves like ordinary hydrogen and can replace ordinary hydrogen in water molecules. Thus, tritium readily cycles through the hydrologic and biologic components of the environment. Tritium has three times the mass of ordinary hydrogen due to the two extra neutrons. Because of this extra mass, water containing tritium evaporates at a slightly slower rate than water containing only hydrogen-1.
The unit of measure of tritium in water is the tritium unit (TU). One tritium unit equals 1 tritium atom in 1018 hydrogen atoms. In SI units, one tritium unit is about 0.118 bequerels per liter (Bq/L), where the bequerel is one decay per second. In picocuries per liter, 1 TU is approximately 3.19 pCi/L. Tritium occurs in very small quantities naturally, being produced in the upper atmosphere by cosmic rays. Natural (pre-nuclear age) levels of tritium in precipitation are on the order of 1 to 5 TU. Nuclear-weapons testing during the 1950s and 1960s created relatively large amounts of tritium in the atmosphere that can be detected in ground water that was recharged during this period. Greatly elevated levels of tritium can be present in ground water contaminated with radioactive wastes.
It hasn't been until recently that the detection of the very miniscule ammounts of Tritium leakage through several feet of rebar, concrete, steel, and lead have been detectible as the units of measure are so minute to be nearly indetectable. As such, they don't pose much of a threat to humans, or other creatures in general. The half-life of Tritium in the typicaly human is roughly ten days, and is of such a low yield of energy to be about as harmful as living in Colorado being bombarded with a multiple increase of Cosmic rays versus people who live closer to sea level. In fact, when measuring the radioactive levels of Tritium you will notice that the K+ ions in bananas are radioactive as well.
Basically, all of this overreacting to 'radioactive' stuff should result in EVERYTHING being banned that's radioactive. If they were so concerned with such low level contamination, they should do away with Limestone rock on the walls of schools (radioactive), granite countertops (radioactive), bananas (radioactive), and all manner of other things that emit EM and positron/neutron radiation on such low levels.
The irony of all the craziness over 'radioactivity' is that on average, people who work near nuclear reactors, or have 'any' exposure on an ongoing basis at a very low level are typically healthier than the crazy people scared of all this radiation floating around.
If you take all the TLD (thermo-luminescent devices) worn by all Department of Energy employees and Nuclear Sub/Carrier personnel to measure very accurately the radiation exposure over a year, and add up every TLD in the DOE and Navy, it is still less radiation than 1 person receives by living in Denver Colorado for a year.
Thus, by this non-sensical IT'S RADIOACTIVE IT MUST BE BAD FOR US logic, we should quarantine Colorado, because obviously it's going to end up becoming a mutated Zombieland where only those highly paranoid, and well adept at using all manner of sharp, blunt, and dangerous instruments for maiming Zombies will survive.