fissile shipping questions

[Lester Slaback <Lester.Slaback@NIST.GOV>]

The DoT and IAEA shipping rules regarding fissile materials get rather 
complex.  Much of this complexity is related to common carrier mode (as 
opposed to exclusive use mode).  I wonder at the need for this complexity 
because it ends up making the rules for exclusive use more complicated than 
they need be.
1. Excluding PuBe sources is anyone aware of non-exempt fissile shipments, 
e.g., >15 grams, via modes other than exclusive use?  Or of a need for such?
2.  If there is a specific need for common carrier shipments what is the 
maximum mass that might be shipped via that mode?  Presumably this number 
is something greater than the 15 g exempt amount and less  than the 1 kg 
NRC threshold for security controls.
3. IAEA ST-1 and 49CFR177.842 restrict the presence of other radioactive 
material shipments near fissile controlled shipments.  Why?  What 
interaction could occur?  Even for neutron source shipments the dose rate 
limits reduce the flux to a level that should be inconsequential in terms 
of possible fissions produced.

Thanks for any history you can provide.
Disclaimer:  the above are the personal musings of the author, and do not 
represent any past, present, or future position of NIST, the U.S. 
government, or anyone else who might think that they are in a position of 
authority.
Lester Slaback, Jr.  [Lester.Slaback@NIST.GOV]
NBSR Health Physics
Center for Neutron Research
NIST
100 Bureau Dr.  STOP 3543
Gaithersburg, MD  20899-3543
301 975-5810 voice
301 921-9847 fax

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