Outgassing Expectations

DOE-HDBK-1132-99

per 100 square centimeters (dpm/100 cm2). Since only the outermost mono-

molecular layers are affected, and since these layers are easily removed by a

simple wiping, the mechanical efforts expended to perform decontamination on

such surfaces will, if any, be minimal.

When the concentration gradients have been relatively large and/or the

exposure times have been relatively long, the affected mono-molecular layers

will range down into the intermediately bound layers (i.e., the relatively tightly to

relatively loosely bound layers). Under such circumstances, the surface

contamination levels will range from relatively low to relatively high (i.e., from a

few hundred to a few thousand dpm/100 cm 2). Because the tritium has now

penetrated beyond those levels that would normally be easily removed,

mechanical efforts expended to decontaminate such surfaces will be more

difficult than those described above.

When the concentration gradients have been large and/or the exposure times

have been long, the affected mono-molecular layers will range all the way

down into the very tightly bound layers. The tritium will have penetrated down

into the actual surface of the material, itself; see " ulk Contamination

Modeling,"below. Under such circumstances, the surface contamination will

range from relatively high to very high levels (i.e., from a few tens of thousand

to several hundred thousand dpm/100 cm 2), and that mechanical efforts

expended to decontaminate such surfaces could be very difficult.

Outgassing Expectations . The phenomenon of outgassing is rarely a

problem under the first of the exposure situations described above (i.e.,

situations in which the concentration gradients have been small and/or the

exposure times have been short). However, when systems that have been

exposed to even small amounts of tritium for long-to-very-long periods of time

are suddenly introduced to room air, or any sudden change in its equilibrium

situation, Reactions (5) and (6), (5a) and (6a), (8), (9), and (9a) can be thought

of as springs, and the initial phenomenon of outgassing can be described as

damped harmonic motion. Under such circumstances, therefore, a relatively

large, initial " uff"of HTO will be released from the mono-molecular layers of

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