Decay in storage, a comment

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

Since there is not any regulatory criterion for releasing RAM for
unrestricted use, e.g., BRC (ignoring decommissioning rules), it would seem
the underlying concept of DIS is that impacts are minimized due to the
inherent short halflife of the material.  There simply is a limited time
for the material to migrate via some unspecified pathway to cause exposure
to the public, during which the material decays to even lower levels.

While it is obviously a judgement call as to what halflife value is
reasonable pushing to increase the halflife criterion without a
corresponding lowering of the release level (lower than non-detectable)
would seem to be contrary to this principle.  If one argues that the
transport time from a landfill to a person is X months for a 60 d
(radionuclide, then that decay factor should be added to the release
criterion to justify some longer lived radionuclide.

I realize I am dancing on the head of a pin here in view of the de minimus
nature of these releases.  But absent a general BRC criterion it would seem
that the underlying DIS presumption cannot (and should not) be stretched
simply on the basis of having adequate storage time to get to
non-detectable levels (whatever that means).
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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