Plant Surfaces - STD-1128-98master0103

DOE-STD-1128-98

Guide of Good Practices for Occupational Radiological Protection in Plutonium Facilities

4.2.1 Plant Surfaces

Good housekeeping practices are essential in keeping plant surfaces clean. Periodic

housekeeping should be performed within contaminated areas to minimize the buildup of

contamination and contaminated waste. Periodic decontamination both within contaminated

glove boxes and in the general work area should be conducted to minimize removable

contamination.

In some instances, it may be appropriate to apply fixatives to minimize the movement of

plutonium contamination. However, it is generally desirable to attempt decontamination

first. If decontaminating is not successful or perhaps, not appropriate for the job scope, a

fixative may be appropriate. If a fixative is used, typically a paint, two layers of fixative

should be used, with the bottom coat yellow and the top coat a different color. When the

yellow begins to show through the top coat, additional fixative should be applied. Also, for

areas which have had a fixative applied over plutonium contamination, a routine

contamination survey should be conducted to assure that no contamination has become

movable over time.

In some cases a strippable coating may be used to allow easy decontamination at the

completion of a job. These strippable coatings are sometimes used to decontaminate areas.

An aerosol fixative is also available that can be pumped into a room, glovebox, or other

work space, that coats all exposed surfaces, including the underside of components. This

allows work to proceed without disturbing contamination.

Note: The use of fixatives may require the approval of Facility Criticality Safety personnel

because fixatives may concentrate or moderate fissionable material.

Outside areas may also require a fixative to minimize the spread of contamination.

Historically, some outside contaminated areas have been covered with asphalt to fix

contamination. This is not a desirable material to use because it creates a mixed hazardous

waste as well as significantly increasing the volume of contaminated material for disposal.

Two substances that currently are used as an interim fixative for outside soil/surface

contamination areas are (1) a derivative of pine tar (toll oil), which forms a non-toxic surface

fixative that is hard and appears to have a relatively durable surface and (2) a mixture of

white glue and water (enduro seal), which is easily sprayed on and sets rapidly to a firm

surface. A water to glue ratio of about 25 to 1 appears to perform well in preliminary tests.

Both of these fixatives are only interim measures because of eventual degradation from the

elements. For more localized areas where a permanent fixative/cover is needed, a sprayable

concrete (Shotcrete) is available. A disadvantage of this material is cracking, which defeats

the sealing surface. Another material that can be used as a carpeting for outside

contamination is a spray-on two-part polymer that provides a flexible, semidurable cover.

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