Re: Leak Testing Radium Sources

[Keith <WELCH@CEBAF.GOV>]

 Ninni Jacob writes:
                                             

>Could someone tell me the correct way to estimate how much activity has
>been removed in a leak test of a radium source?

>I used a proportional counter and calculated the beta activity first.  But
>that came out to be much higher than the gamma activity I obtained for
>Ra-226 by counting the swipe on a Ge-Li detector.

	A  "dumb" question to consider:
	Are you using a "modern" proportional counter with alpha/beta
	discrimination?  If not, your "beta" count is really an alpha plus beta
	count.


>Obviously it has something to do with the daughters.  

	Agreed.  If you're just looking at radium activity on the GeLi, you are
	ignoring daughter activity which is being seen on the proportional.

>But how do I
>estimate the correct activity if I only had a proportional counter,

        My opinion is, you already have, assuming you're not overestimating by
	looking at alphas and betas simultaneously.  The hitch is, does the
	.005 uCi limit apply only to the parent?  I always thought it meant 
	total activity.  If so, you have a leaker.

>because one does not normally count swipes on a Ge-Li detector.
>The only reason I counted it this time was because the activity from the
>proportional counter came out to be greater than 0.005uCi.
>So my question is : Is the source really leaking?

	Again, I'd say yes, provisionally.  But that's just my opinion, and you
know what they say about opinions.........