External Exposure Surveys - STD-1128-98master0110

DOE-STD-1128-98

Guide of Good Practices for Occupational Radiological Protection in Plutonium Facilities

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

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