[ RadSafe ] Ra-226 Static Eliminator Bar

dlawrencenewyork at aol.com dlawrencenewyork at aol.com
Thu Jul 14 15:09:55 CDT 2011


I assume you are attempting to use the 186 KeV energy photpeak with a 4% yield to estimate Ra-226. 

This is generally not the best practice for several reasons. One being the interference of the 185.71 KeV photpeak from U-235 with a 57.2% yield (though in the case of purified Ra-226, this is may not be your main concern even if it is of somewhat unknown provenance). Another confounding factor though is the the higher energy photo peaks from the Rn progeny contributing a significant amount of  Compton-scattered photons - resulting in a continuum of counts under the 186 keV photopeak. When you perform the gamma ray pulse height analysis, you need to ensure that you are adequately to subtracting the Compton continuum counts from the region of interest (ROI) around around your 186 centroid and that the defined ROI includes most of the photopeak without making the it overly wide or you will add even more extraneous contributions to the photopeak region.

I would seriously doubt that you have  damage to your eliminator that would result in a 50% equilibrium ratio without it being painfully obvious.

Best Regards,
David Lawrence

-----Original Message-----
From: Kai Kaletsch <eic at shaw.ca>
To: The International Radiation Protection (Health Physics) Mailing List <radsafe at health.phys.iit.edu>
Sent: Wed, Jul 13, 2011 9:09 am
Subject: Re: [ RadSafe ] Ra-226 Static Eliminator Bar


Mike is correct in saying that some of the radon might wander off. However, 
o get your numbers, you would need > 50% radon emanation and a completely 
pen or unsealed source. Radon emanation for man-made radium compounds is 
sually pretty low (< 1%).
So, I think that, even a leaky source, would not explain your numbers. You 
ould try the experiment again but put the bar in some sort of container for 
0 days (i.e. a few radon 1/2 lives to achieve equilibrium). Even with a 
airly crude container, you should be able to contain more than 50% of 
adon.
My guess is that there is something wrong with the gamma spec library and 
ts getting confused, identifying something as a Ra-226 gamma, that really 
sn't. Ra-226 isn't a very intense gamma emitter. So, even a little bit of 
ross talk from something else in the decay chain would create a large error 
n the Ra-226 reading.
Cheers,
ai

---- Original Message ----- 
rom: "BRISSON Nicolas" <nicolas.brisson at irsn.fr>
o: "The International Radiation Protection (Health Physics) MailingList" 
radsafe at health.phys.iit.edu>
ent: Tuesday, July 12, 2011 9:20 AM
ubject: Re: [ RadSafe ] Ra-226 Static Eliminator Bar

 Mike explained it all.

 Radium 226 has a half-life of 1600 years, radon 222 of 3,8 days, lead 214 
 of 26 min and bismuth 214 of 20 min.

 The only other nuclide you could find with gamma spectrometry is lead 210, 
 but its gamma rays are pretty weak in energy or intensity (13 keV, 22% - 
 47 keV, 4%)

 Nicolas Brisson
 IRSN/DEI/SIAR
 route du Panorama
 92262 FONTENAY AUX ROSES
 tel : +33 1-58-35-87-24
 por :  +33 6-08-76-55-32


 -----Message d'origine-----
 De : radsafe-bounces at health.phys.iit.edu 
 [mailto:radsafe-bounces at health.phys.iit.edu] De la part de Brennan, Mike 
 (DOH)
 Envoyé : samedi 9 juillet 2011 00:31
 À : The International Radiation Protection (Health Physics) MailingList
 Objet : Re: [ RadSafe ] Ra-226 Static Eliminator Bar

 I don't think you should expect the lead and bismuth to be in equilibrium 
 with the radium, as the decay product of radium is radon, and you should 
 expect a certain amount of it to wander off (how much depends on how well 
 sealed the radium source is).  On the other hand, you would expect the 
 lead and bismuth to be in equilibrium with each other, and they are.

 There are several other isotopes in the chain that are there, but I don't 
 recall how easy they are to find in gamma spec.  It probably depends in 
 part on your library.

 -----Original Message-----
 From: radsafe-bounces at health.phys.iit.edu 
 [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of 
 alstonchris at netscape.net
 Sent: Friday, July 08, 2011 3:02 PM
 To: radsafe at health.phys.iit.edu
 Subject: Re: [ RadSafe ] Ra-226 Static Eliminator Bar

 Nicolas

 I do not have a table of half-lives to hand, and I am ashamed to say that 
 I no longer remember the basic U-238 decay chain, but, should the Lead and 
 Bismuth be in equilibrium?  I mean to say, is the device leaking?

 I await the slings and arrows with equanimity.



 Cheers
 cja




 -----Original Message-----
 From: BRISSON Nicolas <nicolas.brisson at irsn.fr>
 To: The International Radiation Protection (Health Physics) MailingList 
 <radsafe at health.phys.iit.edu>
 Sent: Fri, Jul 8, 2011 8:24 am
 Subject: Re: [ RadSafe ] Ra-226 Static Eliminator Bar


 Hi all,

 For once, I won't for help but try to bring a bit of information regarding 
 the
 static eliminator bar I found.

 Some colleagues carried out à gamma spectrometry using HpGe detector (20%,
 p-type).

 Total activity results are given below :
 radium 226 : 75 Mbq +/- 25%
 lead 214 : 34 MBq +/- 15%
 bismuth 214 : 36 MBq +/- 15%



 Nicolas Brisson
 IRSN/DEI/SIAR
 route du Panorama
 92262 FONTENAY AUX ROSES
 tel : +33 1-58-35-87-24
 por :  +33 6-08-76-55-32



 -------------------------------------------------------------------------------------------------------

 From:   "BRISSON Nicolas" <nicolas.brisson at irsn.fr>
 To:     "The International Radiation Protection \(Health Physics\)
 MailingList" <radsafe at health.phys.iit.edu>
 Date:   04/12/2011 10:06 AM
 Subject:        [ RadSafe ]  Ra-226 Static Eliminator Bar
 Sent by:        radsafe-bounces at health.phys.iit.edu




 Hi all,



 2 years ago we had a short discussion about radium-226 static eliminator
 bar (excerpt below).
 At that time I could only find the article mentioned below.


 Last week I found a static eliminator bar from US Radium Corp.


 As the dose rate ranged from 1 mSv/h to 1,6 mSv/h between 5 and 0 cm from
 the bar, we didn’t spend too much time studying it at close range. So I
 would be interested in layouts or any information available about these
 bars



 Thanks,


 Nicolas Brisson
 IRSN/DEI/SIAR
 route du Panorama
 92262 FONTENAY AUX ROSES
 tel : +33 1-58-35-87-24
 por :  +33 6-08-76-55-32


 --------------------------------------------------------------------------------

 From: BRISSON Nicolas <nicolas.brisson at irsn.fr>
 To: radsafe at radlab.nl
 Sent: Wed, 28 October, 2009 20:58:57
 Subject: TR: [ RadSafe ] Ra-226 Static eliminator bar

 Hello all,


 I don't have much information on this topic but you can find an article at
 the web address below.
 American Journal of Public Health (August 1950) :

            http://www.ajph.org/cgi/reprint/40/8/943.pdf



 In this article you can read that these static eliminator bars contained
 25 or 50 µg of radium 226 per linear inch.
 Some Ionotron with radium 226 were manufactured by US Radium Corps.

 In France, you could buy a ionotron t.200 for around 20€ in 1960.
 For a total length of 15 cm, the active part had a length of 5 cm. In the
 safety sheet given with the ionotron, it was said that you were at the
 safe distance from the ionotron at 25 cm. Remember though that it was in
 1960...





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