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Contamination Surveys of the Workplace - doe-std-1128-98_ch10097
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DOE Standard Guide of Good Practices for Occupational Radiological Protection In Plutonium Facilities
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Surveys for Removable Contamination cont'd - doe-std-1128-98_ch10099


DOE-STD-1128-98
This document concerns release to controlled areas only. The detailed
requirements for unrestricted release of materials and equipment are found in
DOE Order 5400.5 (DOE, 1993b). Refer to that document for guidance
regarding unrestricted releases.
4.2.4.3 External Exposure Surveys
To delineate the levels involved, measurements of external exposure should
be made at the time a program is established at all locations where personnel
exposure occurs. Additional photon and neutron measurements should be
made at the same frequency as the contamination surveys. The buildup of
plutonium contamination in glove boxes and on gloves and equipment may
contribute substantially to the external dose rates.
4.2.4.4 Measurement and Survey Techniques
This section discusses four types of contamination surveys that are typically
used in DOE facilities. Surveys for removable contamination include a large-
area wipe survey and a technical swipe or smear survey. Surveys for
total/fixed contamination include a scan survey and a statistically based
survey. These surveys, or a combination of them, are used to survey material
for release from radiological control. The appropriate use of each type of
survey is discussed.
Surveys for Removable Contamination
Two types of surveys are used for removable contamination: a large-area
wipe survey and a technical swipe or smear survey.
A large-area wipe survey is used to detect gross removable contamination. A
large-area wipe survey is typically performed using a large floor cloth and a
dust mop type handle to wipe large areas. This technique tends to concentrate
any low levels of removable contamination that may be present. The surface
to be wiped and the wiping material should be industrially clean (i.e., free of
debris, grease, etc.) to reduce self-absorption of alpha contamination. The
survey is performed by wiping the surface of the area being surveyed and
conducting frequent checks of the cloth using a portable instrument. For
detection of alpha-emitting isotopes, a nonabsorbent material should be used.
Removable contamination will be accumulated and concentrated on the wipe,
increasing the probability of its detection. Checking for contamination is
conducted by placing an alpha measurement instrument approximately 0.25
in. (0.6 cm) from the surface of the wipe for 5 seconds, and the count rate
observed. If there is no increase above background, then the wipe may be
placed in contact with the detector. If no radioactivity above background is
measured, then the material is not contaminated with removable
contamination. If radioactivity above background is measured, the material is
contaminated. Depending upon the specific circumstances, a series of
technical smears may be required to locate and quantify the contamination
within the area covered by the large-area wipe. In most instances, if
contamination is detected on the large-area wipe, decontamination should be
considered.
4-14


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