U.S. Nuclear Regulatory Commission

Clarification of Several Aspects of Removable Radioactive Surface Contamination Limits for Transport Packages

HPPOS-064 PDR-9111210250

Title: Clarification of Several Aspects of Removable

Radioactive Surface Contamination Limits for Transport

Packages

See IE Information Notice No. 85-46 entitled as above and

dated June 10, 1985. Clarification and guidance are

provided on (1) averaging of wipe samples, (2) use of

higher efficiency (>10%) wipe sampling methods, (3)

wrapping of packages (casks), and (4) exclusive-use vehicle

surveys for surface contamination.

AVERAGING OF WIPE SAMPLES: The DOT regulations currently

state in 49 CFR 173.443 (a) that "... the amount of

radioactivity measured on any single wiping material when

averaged over the surface wiped ..." shall not exceed the

limits of 49 CFR 173.443, Table 10. Prior to the

regulatory amendments by DOT in 1983 (Docket HM-169, 48 FR

10238, March 10, 1983), formerly applicable 173.397 (a)

provided that wipe samples could be "... averaged over any

area of 300 cm2 of any part of the package surface." We

understand that it was "not" DOT's intention to disallow

such averaging and further that DOT will consider

processing a future rule change to restore such a provision

to 173.443. In the interim, until the text has been

formally modified, we will continue to consider that

averaging of multiple wipe samples over any 300 cm2 area of

a package surface is an acceptable practice. [Note: Never

changed in DOT 49 CFR 173.443 (a) (1). See 10 CFR 71.87

(h) (i) (1). NRC adopted DOT language.]

USE OF HIGHER EFFICIENCY WIPE SAMPLES: 49 CFR 173.433 (a)

states: "Other methods of assessment of equal or greater

efficiency may be used. When other methods are used, the

detection efficiency of the method used shall be taken into

account and in no case shall the nonfixed contamination on

the external surfaces of the package exceed ten times the

limits listed in Table 10." DOT considers that the

statement "other methods of assessment of equal or greater

efficiency may be used," also includes other wipe sampling

methods wherein the efficiency has actually been

demonstrated to be greater than 10%. Therefore, in effect,

the wipe sample limits stated in 173.443 (a) and (b) and

Table 10 therein, are limits "by default," which do not

take advantage of utilizing an efficiency greater than 10%.

In evaluations of licensees' package surveys, NRC plans to

accept assessments based on efficiencies which have been

appropriately demonstrated to have an efficiency higher

than 10%. The higher efficiency of the wipe sampling method

must be documented and in no case may the removable levels

exceed 10 times the values in Table 10 of 49 CFR 173.443.

WRAPPING OF PACKAGES (CASKS): "Weeping" of contamination

may occur on casks that have been immersed in spent fuel

storage pools. The issue of whether exterior "wrapping" of

casks can be used to achieve compliance with removable

contamination limits has been raised on a number of

occasions. The reply from DOT on this matter read as

follows: "For both NRC-certified and non-NRC-certified

packages, any wrapping must be addressed in the package

design evaluation" (e.g., heat retention since the contents

are a heat source). "For NRC-certified packages this would

include specific mention in the certificate of compliance.

For DOT Specification 7A, Type A, packages, the shipper's

package safety evaluation would have to document the

ability of the wrapping to successfully pass the Type A

tests" (e.g., the wrapping would maintain its closure

integrity during normal conditions of transport).

EXCLUSIVE-USE VEHICLE SURVEYS FOR SURFACE CONTAMINATION:

For packages shipped as exclusive-use by rail or highway,

the provision of 173.443 (b) provides that the removable

(nonfixed) radioactive surface contamination at any time

"during transport" may not exceed "10 times" the limits of

49 CFR 173.443 Table 10. At the "beginning" of transport,

however, the levels may not exceed those stated above.

Further, pursuant to 173.443 (c), any transport vehicle in

which packages are transported within the "factor of 10"

higher values (e.g., above the Table 10 limits), must be

surveyed with appropriate radiation detection instruments

after each use and shall not be returned to service until

the radiation dose rate is below 0.5 mrem/hr and the

removable contamination is below the limits stated above

(49 CFR 173.443, Table 10). An exception to this vehicle

survey requirement is provided by 173.443 (d) for closed

transport vehicles (highway) which are dedicated solely to

the transport of radioactive material packages and are

appropriately marked on the exterior of the vehicle. Also,

in such cases the removable surface contamination on

packages within such vehicles may be at the "factor of 10"

limits at the "start" of transport.

Regulatory references: 10 CFR 71, 49 CFR 173

Subject codes: 7.6, 12.4, 12.17

Applicability: Reactors