Re: shielding contaminants

[eport@nwu.edu (Eli A. Port)]

This problem would be simpler if more were known about the application.  
10E3 reduction in radiation levels may mean several different things.  
The amount of shielding required depends upon the desired reduction is 
in overall radiation levels or a specific region of interest.  The 
background spectrum in the region of interest should be used in 
calculating shielding requirements.  Although graded shields of Pb, Cu, 
and Al can be used, clean virgin lead may be sufficient in many 
applications. Problems in background caused by contamination of steel 
from fallout, refractory markers, or sources included in scrap can be 
eliminated by not using steel.  Most detector manufacturers supply 
shields for detectors.  However, lead brick may be less expensive, can 
be used in configurations of your choice and reused in other applications. 

Feel free to call me at 708-965-1999 if you would like to futher discuss 
this shielding problem.     

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>Try and get a hold of some "old" lead. This however can be quite expensive.
>You might want to consider using a graded shield. That is, use a copper
>liner within the lead shield to get rid of the Pb 210 gammas (low energy)
>and most of the fluorescent x-rays which may originate in the lead.
>
>Just an idea!!
>
>
>
>>> I have a rather unusual shielding problem to solve.  I have to shield some 
>>> scintillation detectors from ambient background radiation, and want to do
>it in 
>>> the most cost effective manner.  The radiation level has to be reduced by a 
>>> factor of 1000.  I have determined the thickness required of lead, steel,
>and 
>>> concrete (in order of decreasing cost) to provide this level of shielding
>for a 
>>> 1 MeV photon (the average background gamma energy I used for the shielding 
>>> calculations).  However, I am concerned that I will be adding as many
>background 
>>> gammas from the shielding material that I am removing if the shielding
>material 
>>> has low-level radiation in it.  Does anyone know which of the three
>alternatives 
>>> will provide the least background?  What are the level of contaminants in
>the 
>>> proposed shielding materials relative to "normal" soil?
>>> 
>>> Thank you in advance,
>>> 
>>> Daniel Low, Ph.D.
>>> 
>>> 
>>>  -----------------------------------------------
>>> |     _/_/_/    _/     Daniel A. Low, Ph.D.     |
>>> |    _/    _/  _/      Assistant Professor      |
>>> |   _/    _/  _/       Mallinckrodt Institute   |
>>> |  _/_/_/    _/_/_/_/     of Radiology          |
>>> |                     Division of Radiation     |
>>> |                         Oncology              |
>>> |                   510 South Kingshighway Blvd.|
>>> |                 St. Louis, MO 63110  USA      |
>>> |               (314) 454-5021 (Office)         |
>>> |             (314) 454-5276 FAX                |
>>> |           low@castor.wustl.edu                |
>>>  -----------------------------------------------
>>> 
>>> 
>>
>>
>
>
>                I know that you believe you understand what you think I said 
>                but I am not sure that what you heard is actually what I meant.
>
>                        Alex Zapantis
>                        Radiation Safety Officer                               
>                        Queensland University of Technology          
>                        Health & Safety Section                             
>                        Locked Bag No.2
>                        Red Hill Qld 4059
>                        AUSTRALIA
>
>                        Ph     : 61 7 864 3566
>                        fax     : 61 7 864 3993
>                        email  : a.zapantis@qut.edu.au
>
>
>
>
ELI A.PORT, CHP, CIH, P.E.
RSSI
eport@nwu.edu
VOICE:708.965.1999, 24X7
FAX:  708.965.1991