Reg Guide 1.86 vs. Nureg 1549. -Reply

[ABELQUIE@ORAU.GOV]

Joe-

This may be old news (and possibly now incorrect), but at the Feb 98
NRC Workshop on these issues, the low DCGLs for Th, U, and Ra in
1549 were discussed.  NRC replied that those numbers were generated
with a screening model (DandD) and should not be considered based on
the 25 mrem/y criterion.  They stated that screening level DCGLs for U,
Th and Ra would be removed from 1549, thus forcing everyone to
perform site-specific analyses to get their DCGLs for these materials. 
Has anyone heard more recent information?

It's likely that site-specific DCGLs for thorium will still be lower than 1.86
values.  Considering that most folks make gross measurements of
thorium surface activity, which implies a certain background level
depending on the surface type assessed, it may be appropriate to
demonstrate indistinguishability from bkg as opposed to compliance with
a low thorium DCGL.  This is called Scenario B in MARSSIM - and may
result in fewer measurements required than if Scenario A were applied. 
NUREG-1505 provides a good discussion of Scenario B.  

As far as Reg Guide 1.86 goes, all licensees planning to initiate
decommissioning planning must use the new D&D rule (25 mrem/y) by
8/20/98, and the supporting Regulatory Guide DG-4006.  Those with
approved D&D plans would be exempt from the new rule.  Also, I do not
think the new rule addresses the unrestricted release of non-real
materials - so 1.86 may continue to be used in that context.

Regards,
Eric Abelquist
abelquie@orau.gov

 

>>> D1.OUT."joseph#u#guido@radian.com" 06/19/98 02:07am >>>
     Has anyone taken a look at the values for thorium published in nureg 
     1549?  These values are orders of magnitude lower than the good
ol'e 
     reg guide 1.86 number (~5 dpm/100 cm2 versus 1000).
     
     My questions are:
     
     How are those currently drafting decommissioning plans dealing with 
     the impending change over to dose based criteria, and potentially the 
     values published in nureg 1549 (when it goes final)
     
     Anyone hear anything from the NRC on how the changeover from reg
guide 
     1.86 is expected to occur, will current licensees be allowed to 
     continue to use it?  until when?
     
     
     
     ----
     
     joe guido
     health physicist
     radian international
     joseph_guido@radian.com
     (916)-857-7368