Fw: Y-90

[Elaine Marshall <emarshall@fnal.gov>]

I had always thought that Sr-90 and Y-90 were pure beta emitters.  However,

I would be concerned about a nuc safety rep saying that they don't need to

be considered in a shielding calculation.  Someone is forgetting about

bremsstrahlung.  Remembering that bremsstrahlung photons have a continuous

energy distribution ranging from the theoretical maximum energy of the beta

particle, this can be quite significant.



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

From: <Jack_Earley@RL.GOV>

To: <radsafe@list.vanderbilt.edu>

Sent: Tuesday, February 12, 2002 2:19 PM

Subject: Y-90





> I was "somewhat" surprised today to hear a nuc safety rep say that since

> Sr-90 is pure beta, it doesn't need to be considered in a shielding

> calculation. When I mentioned that it's in equilibrium w/ Y-90, which

emits

> some significant gammas, I was even more surprised to hear him say Y-90

> doesn't emit gammas. Rather than address it further in the meeting, I

pulled

> up Grove's (Kocher) decay program, which showed only two betas for Y-90;

no

> gamma. But it then lists Y-90m w/ seven gammas ranging from about 2 keV to

> 0.7 MeV. My day for surprises, I guess--I've always associated Y-90 gammas

> w/ 2+ MeV. Sure enough, my 15th edition of the chart shows 202 keV and 2.2

> and 2.3 MeV gammas. So, since I'm apparently not the brightest bulb in the

> lamp, can someone tell me why there's such a difference?

>

> Jack Earley

> Radiological Engineer

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