[ RadSafe ] Rad Toolbox [[was Radon pCi/l to mRem/hr]]
John R Johnson
idias at interchange.ubc.ca
Sun Apr 8 13:45:36 CDT 2007
I think that is wrong because the two "cascading" gamma rays from Yr-90m are
0.202 and 0.695MeV. These total ~0.9 MeV and the beta from Sr-90 is 0.546
The above means that the ground state of Sr-90 is ~ 0.35 MeV below the
"ground state" of Y-90m and therefore Sr-90 decaying to Y-90m is "up energy"
and does not occur.
----- Original Message -----
From: "Jaro" <jaro-10kbq at sympatico.ca>
To: "RADSAFE" <radsafe at radlab.nl>
Sent: Sunday, April 08, 2007 10:52 AM
Subject: RE: [ RadSafe ] Rad Toolbox [[was Radon pCi/l to mRem/hr]]
> Thanks John,
> 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
> 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
> 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
> 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 ?
> -----Original Message-----
> 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
> 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
> you say the main photons are the bremsstralung from these betas.
> John R Johnson, PhD
> CEO, IDIAS, Inc.
> Vancouver, B. C.
> (604) 222-9840
> 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
>> to have.
>> But I was a bit disappointed, when I tested it to see how it displays
>> 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
>> 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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