Determination of Nonfixed Radioactive Contamination (49 CFR 173.433(a))

TM 55-315

3-8. Determination of Nonfixed Radioactive Contamination (49 CFR 173.433(a))

The level of nonfixed radioactive contamination may be determined by wiping an area of 300 square centimeters of the

surface concerned with an absorbent material, using moderate pressure, and measuring the activity on the wiping

material. Sufficient measurements shall be taken in the most appropriate locations to yield a representative assessment

of the nonfixed contamination levels. The amount of radioactivity measured on any single wiping material, when

averaged over the surface wiped, is the contamination level.

3-9. Contamination Limits for Conveyance of Low Specific Activity Materials

Dependent on particular parameters, low specific activity (LSA) materials may be transported by exclusive-use

conveyances or by conveyances that do not meet exclusive use requirements. (49 CFR 173.443 and 173.425 (general),

49 CFR 176.715(a) (vessel), 49 CFR 175.705 (aircraft), 49 CFR 174.715 (rail))

a. Conveyances That do not Meet the Requirements of Exclusive Use or Exclusive-Use Closed Transport

Vehicles but are Used to Transport Low Specific Activity Materials. Any transport vehicle, vessel hold, vessel

compartment, deck area, aircraft, or railcar used for transporting LSA materials must be surveyed after each use with

appropriate radiation detection instruments. The conveyance must not be used again until the radiation dose rate at any

accessible surface is not more than 0.5 millirem per hour and the removable (non-fixed) radioactive surface

contamination, as measured per paragraph 3-8 above is insignificant.

(1) Unpackaged (bulk) LSA materials shall be transported only in exclusive-use closed transport vehicles (49

CFR 173.425(c)).

(2) Packaged LSA materials that are excepted from specification packaging, marking, and labeling may not

be transported by aircraft (49 CFR 175.705 (b)).

(3) Aircraft used routinely for transporting radioactive materials shall be periodically checked for radioactive

contamination. The frequency of checks shall be related to the likelihood of contamination and the extent to which

radioactive materials are carried (49 CFR 175.705(a)).

b. Exclusive-Use Conveyances, Including Transport Vehicles (49 CFR 173.443(c)), Railcars (49 CFR 174.715(a)),

Vessels (49 CFR 176.715(a)), and Air-craft (49 CFR 175.705). Exclusive-use conveyances shall be surveyed after each

use with appropriate radiation detection instruments. They shall not be used again until the radiation dose rate at each

accessible surface is 0.5 millirem, or less, per hour and the removable (nonfixed) radioactive surface contamination is

insignificant.

c. Exclusive-Use Closed Transport Vehicles and Exclusive-Use Railcars (49 CFR 173.443(d)).

These

conveyances shall be surveyed after each use with appropriate radiation detection instruments. They shall not be used

again until the radiation dose rate at each accessible surface does not exceed 10 millirems per hour at the surface or 2

millirems per hour at 1 meter (3.3 feet) from the surface. These conveyances must be stenciled with the words "FOR

RADIOACTIVE MATERIALS USE ONLY" in lettering at least 3 inches (76 millimeters) high in a conspicuous place on

both exterior sides of the vehicle. The vehicles must remain closed except for loading or unloading.

3-10. Contamination Limits for Conveyances Used to Transport Radioactive Materials Other Than Low Specific

Activity Materials

The contamination limits for conveyances used to transport radioactive materials other than LSA materials are the same

as those limits outlined in paragraph 3-9 above.

3-11. Contamination Limits of Packaging

The level of nonfixed (removable) radioactive contamination on the external surfaces of each package offered for

shipment shall be kept as low as practicable. However, there are three different categories for the contamination limits of

packaging.

a. Based on the methods outlined in paragraph 3-8, the contamination level on the external surfaces of the

package shall not exceed the limits listed in table 3-1. Other assessment methods of equal or greater efficiency may be

used if they are according to 49 CFR 173.443(a).

b. On the external surfaces of packages transported in exclusive-use shipments by rail or only on public highways,

the contamination level at the beginning of transport shall not exceed the limits listed in table 3-1. However, during

transport, the contamination level on the outer surfaces may increase, but it shall not be allowed to exceed 10 times the

limits listed in table 3-1. The exclusive-use railcar or transport vehicle must meet the requirements outlined in paragraph

3-9b above.

c. Packages shipped in closed transport vehicles and only over public highways may have exterior surface

contamination levels up to 10 times the limits listed in table 3-1. The exclusive-use closed transport vehicle must meet

the requirements listed in paragraph 3-9c above.

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