OVERVIEW OF TRITIUM - CHARACTERISTICS, SOURCES, AND PROBLEMS

Tritium has certain characteristics that present unique challenges for dosimetry and health-risk assessment. For example, in the gas form, t ritium can diffuse through almost any container, including those made of steel, aluminum, and plastics. In the oxide form, tritium can gener ally not be detected by commonly used survey instruments. In the envir onment, tritium can be taken up by all hydrogen-containing molecules, distributing widely on a global scale. Tritium can be incorporated int o humans through respiration, ingestion, and diffusion through skin. I ts harmful effects are observed only when it is incorporated into the body. Several sources contribute to the inventory of tritium in our en vironment. These are 1) cosmic ray interaction with atmospheric molecu les; 2) nuclear reactions in the earth's crust; 3) nuclear testing in the atmosphere during the 1950s and 1960s; 4) continuous release of tr itium from nuclear power plants and tritium production facilities unde r normal operation; 5) incidental releases from these facilities; and 6) consumer products. An important future source will be nuclear fusio n facilities expected to be developed for the purpose of electricity g eneration. The principal health physics problems associated with triti um are 1) the determination of the parameters for risk estimation with further reduction of their uncertainties (e.g., relative biological e ffectiveness and dose-rate dependency); 2) risk estimation from comple x exposures to tritium in gas form, tritium in oxide form, tritium sur face contamination, and other tritium-contaminated forms, with or with out other ionizing radiations and/or nonionizing radiations; 3) the do se contributions of elemental tritium in the lung and from its oxidize d tritium in the gastrointestinal tract; 4) prevention of tritium (in oxide form) intake and enhancement of tritium (oxide form) excretion f rom the human body; 5) precise health effects information for low-leve l tritium exposure; and 6) public acceptance of tritium leakage and wa ste disposal from reactors and fuel reprocessing plants.