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RE: ...no subject...
The use of a ZnS Scintillator should be sufficient for measuring direct
alpha levels even within a high gamma background, however attempting to
measure direct beta/gamma levels with a plactic scintillator may prove to
be difficult with your external dose rates. I would suggest taking open
window vs closed window ion chamber readings to locate any gross beta
activity.However, you will not be able to quantify 5 Bq/cm2. Perhaps a
strippable paint may be considered as a decontamination technique prior to
transporting or just as an encapsulation method.
> -----Original Message-----
> From: maj_louie_tonry@ddeamc.smtplink.amedd.army.mil
> [SMTP:maj_louie_tonry@ddeamc.smtplink.amedd.army.mil]
> Sent: Wednesday, January 06, 1999 8:14 AM
> To: Multiple recipients of list
> Subject: Re: ...no subject...
>
>
> 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
> +
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> +
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> +
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> +
> + Internet: MAJ_Louie_Tonry@DDEAMC.SMTPLINK.AMEDD.ARMY.MIL
> +
>
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>
> ______________________________ 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
>
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