Contamination

PHYSICAL AND CHEMICAL PROPERTIES

DOE-HDBK-1079-94

Tritium Primer

Contamination

Tritium as HT or HTO will readily adsorb onto the surface of most metals (such as stainless

steel, copper, or aluminum), plastics, and rubbers. The tritium will remain fairly close to the

surface unless the metal is heated to a high temperature. At room temperature, permeation

into these metals is usually extremely slow.

In the case of metal contamination, the tritium remains on or very close to the surface. The

contamination can be removed with water or water vapor if the surface is contaminated with

HTO or with hydrogen (H2 or D2 ) if the contamination is HT. Heating also speeds up the

decontamination process. The initial application of heat to surfaces can also be used to prevent

or lessen the contamination by HT or HTO. Metal surfaces exposed to high pressures of HT

or HTO for extended periods, especially at high temperatures, may allow enough penetration

to cause structural damage to the metal. This is especially true if the decaying tritium causes

a buildup of helium within the structure of the metal.

If adsorbed onto hydrogenous material, the tritium will easily permeate into the material. The

HTO will move much more rapidly into the bulk material than will HT. The permeation rate

varies with the type of material and is accelerated by increasing the temperature. As a result of

this movement, plastics and rubbers exposed to tritium (especially as HTO) are readily

contaminated deep into the bulk material and are impossible to decontaminate completely. After

a period of time, the tritium exchanges with bulk hydrogen and presents little biological risk.

Highly contaminated metal or plastic surfaces may release some of the loosely-bound tritium

immediately after exposure to the contaminating tritiated atmosphere or liquid. This is referred

to as outgassing. The personnel risk from outgassing tritium is generally much less than that

from making unprotected skin contact with the outgassing surface.

Tritium

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