Re: ...no subject...

[maj_louie_tonry@ddeamc.smtplink.amedd.army.mil]

     Heir Feinhals;
     
     Evaluation of surface contamination for alpha can be done with a ZnS 
     scintillator.  It has a selective response to alpha only and will not 
     be disturbed by the gamma or beta component.  However with a direct 
     reading device, you will not be able to distiguish between removable 
     and non-removable contamination.  To accomplish this, smears will have 
     to be performed.  As for the beta component, how about using a plastic 
     scintillator.  The responce would be very low for the gammas and it 
     wouldn't respond to the alphas.  Again, smears would be required for 
     quantifing removable contamination.
     
     When performing the removable smears, liquid scintillation counting is 
     probably your best option for the betas.  You didn't say what types of 
     contamination you had on the casks.  I would assume there is H-3 in 
     which case you almost have to use LSC.  For the remander of the 
     isotopes a good gas flow proportional counter with a thin window would 
     give good results.
     
     I hope this helps.
     
     MAJ Tonry, US Army
     
          
     ====================================================================== 
     + LOUIE TONRY, CHP                                                   + 
     + MAJOR, MS                                                          + 
     + Chief, Radiation Protection Division                               + 
     +                                                                    + 
     + Eisenhower Army Medical Center                                     + 
     + ATTN: MCHF-LOG-HP (Radiation Protection)                           +
     + Box 264                                                            +
     + Ft. Gordon, Georgia 30905-5650                                     +
     +                                                                    + 
     + Voice:     DSN: 773-4692/6392      Civilian: (706) 787-4692/6392   + 
     + Facsimile: DSN: 773-3427           Civilian: (706) 787-3427        + 
     + Internet:  MAJ_Louie_Tonry@DDEAMC.SMTPLINK.AMEDD.ARMY.MIL          + 
     ======================================================================





     


______________________________ Reply Separator _________________________________
Subject: ...no subject... 
Author:  <radsafe@romulus.ehs.uiuc.edu > at Internet-Mail
Date:    1/6/99 3:54 AM


Dear Radsafers
     
Does anybody know a device for direct measuring of fixed and non-fixed 
alpha/beta surface-contamination in presence of gamma dose rates up to 2 
mSv/h?
     
Background:In May 98 contamination at casks for shipping of spent nuclear 
fuel were published. Therefore, the transport of spent nuclear fuel has been 
stopped in Germany. There are different causes for these contaminations:
- insufficient decontamination of the casks and/or tools after lifting out of 
the pool,
- crud particle in micro pores,
- the change of fixed contamination to non-fixed contamination during 
transport.
You can imagine that the reprocessor will find contaminations above 5 Bq/cm² 
when he receives the cask even the operator checked his loaded cask very 
carefully by smear tests. A check of fixed and non-fixed contamination at the 
surface of the cask would be helpful. Smear tests are insufficient for this 
task, normal contamination monitor is disturbed by the gamma radiation of the 
content of the cask.
Any idea?
     
J. Feinhals
Decommissioning and RadWaste Management 
TUEV Nord Hamburg, Germany
feinhals@tuev-nord.de
     
************************************************************************ 
The RADSAFE Frequently Asked Questions list, archives and subscription 
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html
     


************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html