Chemical Properties - hdbk11290015

DOE-HDBK-1129-99

Other properties of tritium are listed below. Additional characteristics are given in Appendix A.

Atomic Weight = 3.01605

Gram Molecular Weight = 6.03210

Diameter of a tritium atom (approximate) = 1.1 Angstroms

Dissociation energy, T2 to 2T = 4.59 eV

Ionization energy, T to T+ e- = 13.55 eV

Half Life = 12.323 +/- 0.004 years

In this handbook, tritium in the form of the oxide (HTO, DTO, and T2O), unless otherwise specified,

is HTO. Likewise, tritium in its elemental form (HT, DT, and T2) is HT.

2.3 Chemical Properties

The electronic configuration of tritium is the same as protium and deuterium. The chemical

properties of the isotopes are also the same. The rates of reaction vary for the different isotopes

due to the difference in the atomic masses. Additionally, the energy provided by the radioactive

decay of tritium provides the activation energy required so that some reactions will occur with

tritium that will not occur with deuterium or hydrogen.

Hydrogen is present in almost all materials. If tritium is present in a material containing hydrogen,

the tritium atoms will exchange with hydrogen atoms to form a tritiated molecule of the material.

2.4 Biological Properties

The body has no need for elemental hydrogen, deuterium, or tritium and does not readily absorb

H2, HT, HD, D2, DT, or T2 from inhaled gases or through the skin. A small fraction of the inhaled

hydrogen isotopes, in gaseous form, is not exhaled, but is dissolved in the blood stream and then

exhaled after a few minutes.

Tritium in the form of water (HTO, DTO, and T2O) is adsorbed through the skin and in the lungs

from inhaled gases. Tritium in water form is readily retained in the body and remains with a

biological half-life of approximately 10 days. Due to the body's ready adsorption of tritium in the

form of tritiated water, exposure to tritiated water in air is up to 25,000 times more hazardous than

exposure to gaseous tritium (HT, DT, and T2).

The Derived Air Concentration (DAC) for tritium is the airborne concentration that, if inhaled over a

one-year period, would produce approximately a 5-rem dose to the "average" worker. The DAC is

derived by the formula:

DAC =

ALI/2400

derived air concentration (Ci/m3)

where

DAC =

ALI =

annual limit of intake (Ci)

breathing volume for the average worker over 1 year in m3

2400 =

.02 m3/min x 60 min/hr x 40 hr/wk x 50 wk/yr

The DACs for elemental tritium and tritiated water [1] are listed in Table 2-1.