Table 1 Hydrogen isotopes

RADIOLOGICAL FUNDAMENTALS

DOE-HDBK-1079-94

Tritium Primer

Nuclear notation uses the chemical symbol (H for hydrogen) and an arrangement of subscripts

and superscripts. The total number of protons and neutrons is shown as a superscript: 1H for

protium, 2H for deuterium, and3 H for tritium. The number of protons (which identifies the

element) is shown as a subscript. However, the common practice of using H, D and T for these

isotopes, respectively, will be followed in this document, except where nuclear reactions are

illustrated.

The atomic masses, symbols, and natural abundances of the three isotopes of hydrogen are given

in Table 1.

Table 1 Hydrogen isotopes

Symbol

Mass

Natural Abundance

(mass

Physical

Common

Name

(%)

units)

Protium

99.985

1.007825

Deuterium

0.015

2.01400

1 10-18

Tritium

3.01605

Sources of Tritium

Tritium occurs naturally in the environment. Reactions between cosmic radiation and gases in

the upper atmosphere produce most of the world's natural tritium. For example,

Tritium converts into water and reaches the earth's surface as rain. An estimated production

rate of 4 106 Ci/yr results in a world steady-state natural inventory of ~70 106 Ci.a

In addition, commercial producers of radioluminescent and neutron generator devices release

about 1 106 Ci/yr. Atmospheric nuclear test explosions from 1945 to 1975 added about

8 109 Ci of tritium to the environment, much of which has since decayed. However, about

5 108 Ci remain in the environment, mostly diluted in the oceans. Underground nuclear tests

appear to add little tritium to the atmosphere. The nuclear power and defense industries now

a. The curie (Ci) is a unit of activity defined as 3.71010 disintegrations per second (dps). A more basic unit

is 1 dps, which is the definition of the becquerel (Bq). Throughout this Primer, the curie will be used instead

of the becquerel.

Tritium

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