Ten Times Rule Clarification Statement from Regulators

["Tom Johnson" <tjohnson@radtrain.com>]

So many people have asked for this that I think it is worthwhile to post it.
I call it the clarification for the ten times rule, but some of you may not
agree on the clarificaiton part.

Tom Johnson
tjohnson@radtrain.com


Clarification of Several Aspects of Removable Radioactive
Surface Contamina tion 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.