[ RadSafe ] TFP - next questions - Understanding Limitations of Analytical Data

Fri Jan 6 07:52:33 CST 2006

OK - I will contribute now, not in defense of anyone or anything - except
hopefully good science...  I was waiting until I had more to report. 

Good questions on the radioanalytical processes Steven and Keith. Thanks!

I personally still have some concerns about the effectiveness of
decontamination steps in the Sr method. K-40, if it were present, would be
effectively removed using the steps described so I don't see any problem
there. Radium and other naturally occurring nuclides, however, might or
might not be removed. The repeated rinses could, possibly, maybe, have some
effect. Consider that RaCO3 does buck the trend of decreasing solubility as
one goes down group II elements. 

Although we may have concerns or questions, without any direct experience
with this approach I don't see how we can decide whether this is an adequate
procedure or not. We need more information. How was the method validated?
Was decontamination from naturally occurring radio-interferences considered?
If so, perfect! If not, what is the effect on the data?

To Steven Frey's suggestion that chemiluminescence may play a role: my
experience tells me that CL is relatively unlikely with the cocktail mixture
described. Given the transient nature of the phenomenon, the repeated counts
used in the method would probably provide clear indications of a problem.
This level of detail in data was not provided in the paper.

Keith - Your suggestion about splitting up counts is a very good one. I can
imagine that the radiochemist involved might be open to your observations.
But there is certainly nothing 'wrong' with the method described for
acquiring backgrounds. 

There are a lot of open questions. 

Has anyone tried contacting the individuals involved to share concerns or to
get answers?  Before we make conclusions and especially before we publicly
cast aspersions on this work, it is our responsibility as professionals to
get adequate information. We would all expect at least the same if our work
was being questioned. 

To this end, I am taking steps to initiate discussion with different
individuals involved with this testing (not only on the radioanalytical
questions but also on the gross beta questions). 

I will post information as I receive (or don't receive) it. Let the facts
decide.

Bob Shannon

Bobshannon91 at earthlink.net 

-----Original Message-----

From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On Behalf
Of Bradshaw, Keith

Sent: Thursday, January 05, 2006 4:03 AM

To: radsafe at radlab.nl

Subject: RE: [ RadSafe ] TFP - next questions

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>

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