Table 4 -1. Surface Contamination Values,(a) dpm/100 cm2

DOE-STD-1136-2004

Guide of Good Practices for Occupational Radiological Protection in Uranium Facilities

Table 4 -1. Surface Contamination Values,(a) dpm/100 cm2

Total

(b, d)

Nuclide

Removable

(b, c)

(Fixed+Removable)

(g)

U-nat, 235U, 238U, and associated decay products

1000

5000

Transuranics, 226Ra, 228Ra, 230Th, 228Th, 231Pa, 227Ac, 125I,

500

129

Th-nat, 232Th, 90Sr, 223Ra, 224Ra, 232U, 126I, 131I, 133I

200

1000

Beta-gamma- emitters (nuclides with decay modes other

1000

5000

than alpha emission or spontaneous fission) except 90Sr

(e)

and others noted above

(f)

10,000

N/A

Tritium and tritiated compounds

(a) The values in this table, with the exception noted in footnote (e), apply to radioactive contamination deposited on, but not incorporated

into the interior or matrix of, the contaminated item. Where surface contamination by both alpha- and beta-gamma emitting nuclides

exists, the limits established for alpha- and beta-gamma-emitting nuclides apply independently.

(b) As used in this table, dpm (disintegrations per minute) means the rate of emission by radioactive material as determined by correcting

the counts per minute observed by an appropriate detector for background, efficiency, and geometric factors associated with the

instrumentation.

(c) The levels may be averaged over one square meter provided the maximum surface activity in any area of 100 cm2 is less than three

times the value specified. For purposes of averaging, any square meter of surface shall be considered to be above the surface

contamination value if: 1) From measurements of a rep resentative number of sections it is determined that the average contamination

level exceeds the applicable value; or 2) it is determined that the sum of the activity of all isolated spots or particles in any 100 cm 2 area

exceeds three times the applicable value.

(d) The amount of removable radioactive material per 100 cm2 of surface area should be determined by swiping the area with a dry filter or

soft absorbent paper, applying moderate pressure, and then assessing the amount of radioactive material on the swipe with an

appropriate instrument of known efficiency. (Note--The use of dry material may not be appropriate for tritium.) When removable

contamination on objects of surface area less than 100 cm 2 is determined, the activity per unit area shall be based on the actual area and

the entire surface should be wiped. It is not necessary to use swiping techniques to measure removable contamination levels if direct

scan surveys indicate that the total residual surface contamination levels are within the lim its for removable contamination.

(e) This category of radionuclides includes mixed fission products, including the 90Sr which is present in them. It does not apply to

90Sr which has been separated from the other fission products or mixtures where the

Sr has been enriched.

(f) Tritium contamination may diffuse into the volume or matrix of materials. Evaluation of surface contamination shall consider the extent

to which such contamination may migrate to the surface in order to ensure the surface contamination value provided in this appendix is

not exceeded. Once this contamination migrates to the surface, it may be removable, not fixed; therefore, a "Total" value does not

apply.

(g) (alpha)

Scan Survey for Fixed Contamination

A scan survey for fixed contamination requires passing a detector attached to a portable instrument

over the surface of the area being surveyed at a fixed, known scan speed and at a specified distance from

the surface. Typically, the scan speed is 2 in./s (5 cm/s) and the maximum distance is 0.25 in. (0.6 cm) for

alpha-contamination instruments. A scan survey should be used to survey material that resides in an area

controlled for contamination purposes, an area where unsealed radioactive sources are used, or an area

surrounding an area controlled for contamination purposes. A scan survey in conjunction with a swipe

survey should be used to release from radiological control material with a total surface area less than 5 ft2

(0.46 m2). A statistically-based survey, which will be discussed later, should be used to release from

radiological control material with a surface area greater than 5 ft2(0.46 m2).

During the performance of scan surveys, the audible response of the instrument is faster than the

needle deflection. Therefore, audible response should be used in conjunction with meter readings. For

alpha surveys, the surveyor should pause for 3 to 5 seconds each time an individual pulse is detected in

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