Uncertainties and Limitations - doe-std-1128-98

DOE-STD-1128-98

Total

Radionuclide

Removable 2,4

(Fixed + Removable) 2,3

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

7 1,000

7 5,000

Transuranics, Ra-226, Ra-228, Th-230,

500

Th-228, Pa-231, Ac-227, I-125, I-129

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

200

1,000

131, I-133

Beta-gamma emitters (nuclides with decay modes other

1,000

5,000

than alpha emission or spontaneous fission) except Sr-

90 and others noted above5

Tritium and tritiated compounds6

10,000

N/A

The values in this appendix, with the exception noted in footnote 5 below, 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 exist, the limits established for alpha- and beta-gamma-emitting

nuclides apply independently.

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.

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 representative 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 cm2 area exceeds three times the applicable value.

The amount of removable radioactive material per 100 cm2 of surface area should be determined by swiping the area

with 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 cm2 is determined, the

activity per unit area shall be based on the actual area and the entire surface shall 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 limits for removable contamination.

This category of radionuclides includes mixed fission products, including the Sr-90 which is present in them. It does

not apply to Sr-90 which has been separated from the other fission products or mixtures where the Sr-90 has been

enriched.

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.

(alpha)

4.1.4 Uncertainties and Limitations

Because plutonium is relatively difficult to detect and quantify, it is important to

consider the uncertainty in the measurements when designing a plutonium

monitoring program. Although the design objective of the facility will likely be no

airborne plutonium contamination, the reality will be a measurement that ensures

airborne plutonium is below an acceptable lower limit of detection. The sampling and

monitoring program will need to be designed not only for prompt detection of

4-3