[ RadSafe ] Rad Toolbox [[was Radon pCi/l to mRem/hr]]
jaro-10kbq at sympatico.ca
Sun Apr 8 12:52:46 CDT 2007
In a discussion on Radsafe a few years ago, someone said that Sr-90 "beta
decays 99.9979% of the time to Y-90m (3.19 hour half-life). This Yttrium has
numerous gamma emissions. Its predominant gamma emissions are two gammas
each about 15 keV (a total of 6+% of the time), a 202 keV (96.6% of the
time), and a 480 keV gamma (91% of the time) with a 2.18 MeV gamma occurring
8.7 E-8% of the time and a 2.32 MeV gamma occurring 0.00173% of the time.
A vanishingly small percentage of the time (1 - .999979), Sr-90 beta decays
directly to Y-90 (2.671 days half-life). This Y-90 has virtually no gamma
emissions and beta emissions of 79 keV, 401 keV, and 432 keV."
Sorry, I don't have the exact citation anymore, but I suppose it should be
possible to find it in Radsafe archives.
Anyway, the point is that you apparently do not agree with the quoted
statement, if I understand correctly ?
From: John R Johnson [mailto:idias at interchange.ubc.ca]
Sent: Sunday, April 08, 2007 1:28 PM
To: Jaro; RADSAFE
Subject: Re: [ RadSafe ] Rad Toolbox [[was Radon pCi/l to mRem/hr]]
I think the one from BNL is the best, but I've lost its address.
Question; Why do you want information on Y-90m for Sr-90 decay? Sr-90
decays directly to the ground state of Y-90 with an Emax beta of 0.546 Mev.
Y-90 decays (0.02%, Emax = 0.52 MeV) to an excited state (1.75 MeV) of
Zr-90. The main decay is to the ground state of Zr-90. You are correct when
you say the main photons are the bremsstralung from these betas.
John R Johnson, PhD
CEO, IDIAS, Inc.
Vancouver, B. C.
idias at interchange.ubc.ca
----- Original Message -----
From: "Jaro" <jaro-10kbq at sympatico.ca>
To: "RADSAFE" <radsafe at radlab.nl>
Sent: Sunday, April 08, 2007 8:08 AM
Subject: RE: [ RadSafe ] Rad Toolbox [[was Radon pCi/l to mRem/hr]]
>I installed Rad Toolbox software on my PC, thinking it will be a handy tool
> to have.
> But I was a bit disappointed, when I tested it to see how it displays data
> on Sr-90 decay.
> Like many other reference sources, it omits the Y-90m isomer, which is
> normally the intermediate decay product, prior to Y-90.
> If it wasn't important, I guess I wouldn't mind very much.
> But in this case, if users are unaware of the intermediate decay product,
> they are led to believe that Sr-90 is a radioisotope energy source without
> any gamma emissions (thus very desirable, as bremsstrahlung X-rays are
> easier to shield than gammas).
> I wonder how many other such omissions are present in Rad Toolbox &
> software ?
> Is anyone aware of any software that is more accurate ? (Thnx)
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