Radiolysis Reactions

DOE-HDBK-1132-99

But, because a classic inorganic chemical reaction like that depicted in

Equation (7) can be expected to reach equilibrium in a time frame that ranges

from many hours to several days under the conditions normally found in nature,

classic inorganic chemical reactions of this type are not necessary for this

discussion.

Radiolysis Reactions. It was noted previously in Section 2.10.4 that the range

of the tritium beta is very short. As a consequence, it follows that virtually all of

the energy involved in tritium beta decay will be deposited in the immediate

vicinity of the atoms undergoing decay. When the medium surrounding the

decaying atoms is tritium gas, tritiated water, or tritiated water vapor in

equilibrium with its isotopic counterparts, reactions such as those presented in

Equations (8) and/or (9) bellow can be expected to dominate. When the

medium surrounding the decaying atoms is not a medium that would normally

be expected to contain tritium, however, an entire spectrum of radiolysis

reactions can be expected to occur.

For typical, day-to-day operations, the most common type of radiolysis

reactions in the tritium community can be expected to occur at the interface

between the air above a tritium contaminated surface and tritium contaminated

surface itself. For these types of reactions, some of the energy involved in the

tritium decay process can be expected to convert the nitrogen and oxygen

components in the air immediately above the surface (i.e., the individual N 2 and

O2 components in the air) into the basic generic oxides of nitrogen, such as

nitric oxide, nitrous oxide and nitrogen peroxide (i.e., NO, N 20, and NO2,

respectively). As the energy deposition process continues, it can also be

expected that these simpler oxides will be converted into more complex oxides,

such as nitrites and nitrates (i.e., NO 2s and NO3s, respectively). Because all

nitrite and nitrate compounds are readily soluble in water (and/or water vapor),

it can further be expected that a relatively large percentage of the available

nitrites and nitrates in the overpressure gases will be absorbed into, and/or

dissolved into, the mono-molecular layers of water vapor that are actually part

of the surface. (See " odeling the Behavior of Tritium"in Section 2.10.6,

below.) With the available nitrites and nitrates now an integral part of the

mono-molecular layers of water vapor, it can finally be expected that the most

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