[ RadSafe ] Ra-226 Static Eliminator Bar
BRISSON Nicolas
nicolas.brisson at irsn.fr
Wed Aug 24 08:14:25 CDT 2011
Hey all,
I have been out of the office for quite some time now, just as the guy from the lab which carried out the measurement.
I will pass him your remarks so that he can check the modelling.
The bar was found in the middle of garbage and was damaged, so radon leaks weren't unexpected. We even found contamination by radon progeny on the external surfaces of the bar.
Given the conditions of our "emergency" operation, we didn't try to get accurate measurements (length, thickness,..) of the bar and its components, so I think that the main problem with the radium activity (quantified with the 186 keV peak) is mainly due to inaccurate modelling of bar : thickness and metal composition of the "shield".
I had some gamma spectrometry on another radium source found on the same day reworked by the lab because of this problem. For this one I knew which activity to expect, which wasn't the case for the bar.
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 Harry Reynolds
Envoyé : vendredi 15 juillet 2011 15:50
À : The International Radiation Protection (Health Physics) Mailing List
Objet : Re: [ RadSafe ] Ra-226 Static Eliminator Bar
I would think that if you have a significant leak of Rn-222, you would be able to detect a buildup of removable particulate progeny on the external surfaces.
-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of dlawrencenewyork at aol.com
Sent: Thursday, July 14, 2011 2:10 PM
To: radsafe at health.phys.iit.edu
Subject: Re: [ RadSafe ] Ra-226 Static Eliminator Bar
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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