 | This articleneeds additional citations forverification. Please helpimprove this article byadding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Tritiated water" – news ·newspapers ·books ·scholar ·JSTOR(May 2013) (Learn how and when to remove this message) |
 | |
 | |
| Names | |
|---|---|
| IUPAC name [3H]2-water | |
| Systematic IUPAC name (3H2)Water | |
Other names
| |
| Identifiers | |
3D model (JSmol) | |
| ChEBI | |
| ChemSpider |
|
| MeSH | tritium+oxide |
| |
| |
| Properties | |
| T2O or3H2O | |
| Molar mass | 22.0315 g·mol−1 |
| Appearance | Colorless liquid[1] |
| Density | 1.21 g/mL |
| Melting point | 4.48 °C (40.06 °F; 277.63 K)[3] |
| Boiling point | 101.51 °C (214.72 °F; 374.66 K) |
| Acidity (pKa) | 15.21[2] |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Tritiated water is aradioactive form ofwater in which the usualprotium atoms are replaced withtritium atoms. In its pure form it may be calledtritium oxide (T2O or3H2O) orsuper-heavy water. Pure T2O is a colorless liquid,[1] and it iscorrosive due to self-radiolysis. Diluted, tritiated water is mainly H2O plus some HTO (3HOH). It is also used as atracer for water transport studies in life-science research. Furthermore, since it naturally occurs in minute quantities, it can be used to determine the age of various water-based liquids, such as vintagewines.
The namesuper-heavy water helps distinguish the tritiated material fromheavy water, which containsdeuterium instead.
Tritiated water is primarily studied as a dilute solution within light water. Here, the proportion of the light, hydrogen tritium oxide is strongly favoured versus the more negligible heavy, double tritium oxide, as the conversion reaction has anequilibrium constant of 3.42 at room temperature.[6]
The molecules then experiencebeta decay and formation of thehydroxyl or tritoxyl radical via:
The average electron energy of the beta decay is 5.7keV. The energy required to break hydrogen-oxygen bonds in water is three orders of magnitude lower at 5.2 eV. This leads to many radiolysis events:
Many subsequent reactions occur, but primarily result in recombination to water, or the escape of molecular hydrogen and oxygen gas, alongside thehelium-3.
Studies of tritiated water often prefer to describe the concentration by the measurable radiation level incuries per liter (Ci/L) orterabecquerels per liter (TBq/L), rather than the species proportion.
In oneCEA study, relatively highly tritiated water at 1,800 Ci/L or 74 TBq/L (0.12% HTO, negligible T2O) was left to self-radiolyze for 56 days in three volumes. In the 300 mL volume, the primary gases collected were H2 at 2.54mmol, O2 at 1.31 mmol, and3He at 0.13 mmol. Thus in this geometry, for each tritium decay, roughly twenty water molecules were permanentlydissociated.[6]
Tritiated water can be used to measure an organism'stotal body water (TBW). Unlikedoubly labeled water this method relies onscintillation counting. Tritiated water distributes itself into all body compartments relatively quickly. The concentration of tritiated water inurine is assumed to be similar to the concentration of tritiated water in the body. TBW is determined from the following relation:
| This sectionneeds additional citations forverification. Please helpimprove this article byadding citations to reliable sources in this section. Unsourced material may be challenged and removed. Find sources: "Tritiated water" – news ·newspapers ·books ·scholar ·JSTOR(September 2023) (Learn how and when to remove this message) |
Tritium is radioactive and a low energybeta emitter.
While HTO is produced naturally bycosmic ray interactions in the stratosphere, it is also produced by human activities and can increase local concentrations and be considered an air and water pollutant. Anthropogenic sources of tritiated water includenuclear weapons testing,nuclear power plants,nuclear reprocessing and consumer products such as self-illuminating watches and signs.
HTO has a shortbiological half-life in the human body of 7 to 14 days, which both reduces the total effects of single-incident ingestion and precludes long-termbioaccumulation of HTO from the environment. The biological half life of tritiated water in the human body, which is a measure of body water turn-over, varies with the season. Studies on the biological half life of occupational radiation workers for free water tritium in a coastal region ofKarnataka, India, show that the biological half life in the winter season is twice that of the summer season.
If tritium exposure is suspected or known, drinking uncontaminated water will help replace the tritium from the body. Increasing sweating, urination or breathing can help the body expel water and thereby the tritium contained in it. However, care should be taken that neitherdehydration nor a depletion of the body'selectrolytes results as the health consequences of those things (particularly in the short term) can be more severe than those of tritium exposure.[citation needed]
