NUREG-1400 Release Fractions

["Sorensen, Scott" <ssorensen@doeal.gov>]

Greetings!

NUREG-1400, Air Sampling in the Workplace (Sept. 1993), adopts the use
of Allen Brodsky's "Magic Number" of 1e-6 in its methodology for
evaluating potential annual intake from airborne hazards.  However, the
"Magic Number" is then modified by release fractions from NUREG-1140, A
Regulatory Analysis on Emergency Preparedness for Fuel Cycle and Other
Radioactive Material Licensees (June 1985).  These release fractions are
based on "severe facility fire" scenarios.  NUREG-1400  states that
their use is "generally suitable for releases to air in the workplace."

Does anyone know what is the basis behind this statement?  It appears to
me that the NUREG-1140 release fractions were intended to be used in
accident analyses without modification by the Magic Number.  As such,
why is it appropriate to modify the Magic Number by these values when
used to guestimate the need for air sampling at facilities operating
under normal conditions?  Please note that NUREG-1400's use of release
fractions result in a less conservative guestimate.

Appreciate your thoughts...

Scott A. Sorensen
ssorensen@doeal.gov