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The
IAEA, in its 1996 Regulations/Recommendations has changed the regulated activity
from a single value (70 Bq/gm) for all nuclides, to a nuclide-specific activity.
Other people on this list can far batter explain the scientific basis for
this.
For
example, the listed activity concentration for natural uranium is 1 x 10^0
(i.e., 1) Bq/gm. For Thallium 201, it's 1 x 10^2, or 100
Bq/gm.
BUT,
there is also an exception for "natural materials and ores containing naturally
occurring radionuclides ... provided the activity concentration does not exceed
10 times the values specified..."
The
proposed US rule was published April 30, 2002, so the proposal is almost a year
old, and is available on the US DOT's hazmat web page:
http://hazmat.dot.gov/rules/99_6283_1.htm (Text
Version)
http://hazmat.dot.gov/99_6283_1.pdf (Adobe
version)
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