Chemical Properties - hdbk10790023

Tritium Primer

DOE-HDBK-1079-94

PHYSICAL AND CHEMICAL PROPERTIES

With one unimportant exception, tritium is the weakest beta emitter known. The range of the

most energetic tritium beta particles is only about 5 mm in air or 0.005 mm in water or soft

tissue. This range makes it a nonhazard outside the body, but presents a detection problem.

Where other radioisotopes can be detected by virtue of their penetrating radiation, tritium has

to be introduced directly inside the detector or counter to be measured.

Chemical Properties

Laboratories that have large quantities of tritium usually handle it in the form of HT. However,

at any time the tritium may be stored on metal getter beds (such as titanium, zirconium, or

uranium). These beds form weak chemical compounds with hydrogen. Some of the beds are

stable in air; and others are not and can only be used in certain atmospheres. The tritium is

released (or delivered) by heating the beds to the required temperature.

Laboratories may also handle tritiated gases (such as ammonia and methane) and other

compounds. By far the most common of these is HTO, which is formed from HT whenever it

is exposed to oxygen or water vapor. The conversion reactions are oxidation and exchange:

oxidation

2HT + O2

2HTO

2T2 + O2

2T2O

exchange

HT + H2O

H2 + HTO

T2 + H2O

HT + HTO

These reaction rates are increased by radiation (from nearby tritium at high concentrations),

heat, or the presence of metal catalysts (especially palladium or platinum). All chemical

reactions involving hydrogen can also be performed with tritium, sometimes at a higher rate

if the tritium concentration is high enough to catalyze the reaction. One of the most important

reactions occurs when a tritium atom exchanges with a loosely bonded hydrogen atom of an

organic molecule. However, where HT is dissolved in water (H2O), the exchange process is

fairly slow because the hydrogen in is tightly bonded and the reaction is not catalyzed.

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Tritium