[ RadSafe ] TFP - next questions

Thu Jan 5 07:11:17 CST 2006

Another "gee whizz" fact cluttering up my brain...

"Secular Equilibrium" from Attix "Introduction to Radiological Physics
and Radiation Dosimetry" 1986, p. 112

"The practical cases to which this terminology is applied usually
include a very long-lived parent, hence the use of the word 'secular' in
its sense of 'lasting through the ages'."

Charlie Ellars
RSO
QSA Global, Inc.
40 North Ave.
Burlington, MA 01803
(781) 272-2000 X298

>>> "Bradshaw, Keith" <keith.bradshaw at niras.co.uk> 01/05/06 5:03 AM
>>>

Thanks for finding this again James.  This came up on RADSAFE a couple
(?)
of years ago.

I doubt I'm alone in thinking simply precipiting carbonates is not
specific
enough for Sr-90 analysis.  A whole range of natural (and artificial)
radionuclides would carry through the procedure.  Radium for example,
but
there's more.

The counting procedure also seems a bit odd.  The Quantulus can be set
to
alternate blank-sample-blank-sample, many times over, to iron out
background
variation over long count times.  Here, they seem to have opted for 4
repeat
counts of 100 minutes for the sample, but a single long 5000 minute
count
for the background.  Probably would have been better to divide the
total
time into 20 or so equal blank-sample cycles.

To be fair, it wouldn't be the first time that the reported procedure
is not
actually what has been done.  Perhaps in reality there was more.  But
on the
basis of what's written I have doubts, as explained above.  It's a
pity,
because these are hard won valuable samples.

>P.S. What is "secular equibrium"?  It sounds like something that 
>might happen on Dick Cheney's secret energy task force.

I've always thought it's an odd phrase too.  In this context it means
Sr-90
decays to Y-90, which is itself radioactive.  Because the Y-90 half
life is
very short compared to the Sr-90 half-life, the Y-90 activity will
"grow in"
any separated Sr-90, and eventually the activities of the two will
become
essentially equal.  After 7 Y-90 half-lives (or about 19 days) the
Y-90
activity will be within 1% of the Sr-90 activity.

Personal views only

keith.bradshaw at niras.co.uk

web:  www.niras.co.uk

-----Original Message-----
From: James Salsman [mailto:james at bovik.org]
Sent: 04 January 2006 19:39
To: radsafe at radlab.nl
Subject: Re: [ RadSafe ] TFP - next questions

> At some point several years ago, there was a semi-detailed
> description of the method being used by the tooth fairy
> project to analyze teeth for Sr.  Can anyone point me to this post?

The following is quoted from pp. 23-24 and 49 of:
  http://mtafund.org/prodlib/radiation_health/final_report.pdf

<CUT>

**********************************************************************
AMEC Nuclear Holdings Limited (no. 3725076), AMEC NNC Limited (no.
1120437), National Nuclear Corporation Limited (no. 2290928), STATS-NNC
Limited (no. 4339062) and Technica-NNC Limited (no. 235856).  The
registered office of each company is at Booths Park, Chelford Road,
Knutsford, Cheshire WA16 8QZ except for Technica-NNC Limited whose
registered office is at Citygate, Altens Farm Road, Aberdeen,
Aberdeenshire, AB12 3LB.  AMEC NNC's head office and principal address
is Booths Park and the switchboard number is 01565 633800.  
The AMEC NNC website is www.amecnnc.com

Any request, advice, information or opinion in this message which does
not relate to the business of any of the above companies is not
authorised by any of the above companies.  Where this message does so
relate,  it is sent by the relevant company (as above) and is
confidential and intended for the use of the individual or entity to
whom it is addressed.  The content is subject to contract and, unless so
stated, does not form part of any contract.  If you have received this
e-mail in error please notify the AMEC NNC system manager by email at
eadm at amecnnc.com.
**********************************************************************

_______________________________________________
You are currently subscribed to the RadSafe mailing list

Before posting a message to RadSafe be sure to have read and understood
the RadSafe rules. These can be found at:
http://radlab.nl/radsafe/radsaferules.html

For information on how to subscribe or unsubscribe and other settings
visit: http://radlab.nl/radsafe/

On October 10th 2005, we changed our name to QSA Global Inc. 
As QSA Global Inc., we remain committed to providing you with the same level of world class service you have come to expect from AEA Technology QSA, Inc.
***********************************************************************
This transmission contains information which may be confidential and 
which may also be privileged. It is intended for the named addressee 
only. Unless you are the named addressee, or authorized to receive it 
on behalf of the addressee you may not copy or use it, or disclose it 
to anyone else. If you have received this transmission in error please 
contact the sender. Thank you for your cooperation. 
***********************************************************************
For more information about QSA Global Inc., formerly 
AEA Technology QSA, Inc.,  please visit
our website at http://www.qsa-global.com