One common technique for tracking a drug's fate is to label its molecular framework with heavier isotopes of hydrogen (either deuterium or tritium). (science.sciencemag.org)
Those experiments require a radioactive isotope of hydrogen called tritium to be produced on site. (scientificamerican.com)
The article discussing the possibility of generating energy using small - scale nuclear fusion suggested that both deuterium and tritium are stable isotopes of hydrogen. (newscientist.com)