Re: Sr/Y-90

[Joel L Lazewatsky <joel.lazewatsky@bms.com>]

Jack,



I wonder if there is some confusion in how the table is being read.  To answer

both responses, Y-90m can be produced by a number of reactions, including

Y-89(n,gamma), Y-90(d,p), even Nb-93(n,alpha) and Sr-88(alpha,d).  It isn't made

by decay of Sr-90.  If it were, then all but the most decayed Y-90 derived from Sr-90

would be screaming with gamma photons since the half lives differ by only x20.

This is clearly not the case as the first respondent indicates.  Neither we nor

anybody else that I know of has ever observed significant numbers of

682, 480 or 202 keV photons in samples of Y-90.



As I said, I don't have access to the later Table of Isotopes, but I am pretty

confidant that Y-90m and its gamma radiation has not been discovered in

the decay products of Sr-90 in the last 20 years.  This is supported both by

data and common sense.  If this has changed, the decrease of the 100%

branching to Y90 must be extremely small given the known characteristics (i.e.

pure beta emission) of virtually all Y-90 used for medical purposes.  This pure

beta is one of its principle attractions (and the cause of some difficulties)

for radionuclide therapy.



If there is something new in this, I would very much like to know about  it.

The numbers quoted by the second response related to the branching in the

decay of the Y-90m, not to the Sr-90 or the production of Y-90.  The

question is:  What fraction of Sr-90 decays result in Y-90m? What

fraction in Y90? Those are the critical numbers.  If a later version of

T of I gives anything other than 0% and 100% respectively, I would really

like to know.



Joel Lazewatsky, Ph.D.

Bristol-Myers Squibb Medical Imaging

N. Billerica, MA



Any opinions expressed are strictly mine and do not necessarily reflect those

of my employer.



Jack_Earley@RL.GOV wrote:



> Two of the many responses I've received are shown below. At this point,

> we're not doing chemical extractions (we'll save that for the Pu inventory

> balance and disposal characterization). This is old fuel; it's been in

> storage for over 25 years; the primary component is Cs-137. So this is not

> pure Sr-90, if that's been a point of confusion.

>

> <<I think we've got Sr-90/Y-90 confused with Y-90.  If you do a chemical

> extraction of Y-90 to obtain pure Y-90, its all beta.  I think the Sr-90

> goes to Y-90m to Y-90.  >>

>

> <<if Sr-90 does NOT decay to Y-90m, then where in the world does the Y-90m

> come from?  Out of thin air? I have also watched the RADSAFE e-mail traffic

> on this issue.  Many folks appear to be using older Table of Isotopes

> versions which may have either been wrong on this issue or misleading and

> could have been updated/corrected in later iterations of the Table of

> Isotopes.  By the way, the absolute latest "Table of Isotopes" is the 8th

> Edition, Firestone, Shirley, Editors with Baglin, Chu, and Zipkin as

> Assistant Editors, Wiley-Interscience 1996; ISBN 0-471-14918-7.  I checked

> this Table of Isotopes--it appears to say essentially the same thing as the

> 1986 Table of Isotopes, except that the percent of time of the isomeric

> transition of Y-90m is specified as 99.9982% instead of the 1986 percent of

> 99.9979% and other minor changes in energy level values, etc.>>

>

> Does this affect anyone's responses?

>

> Jack Earley

> Radiological Engineer

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