[ RadSafe ] Radiation in landfills

[John R Johnson]

George

If I recall correctly from working with the "pure"  beta emitters H-3, C-14 
and Pm-147, the intensitiy of the internal bremstrahlung photons are liner 
on a log normal scale from 0 to the end point energy.

John

----- Original Message ----- 
From: "Geo>K0FF" <GEOelectronics at netscape.com>
To: "Brennan, Mike (DOH)" <Mike.Brennan at DOH.WA.GOV>; "John R Johnson" 
<idias at interchange.ubc.ca>; "Robert D Gallagher" 
<rdgallagher at nssihouston.com>
Sent: Tuesday, July 17, 2007 2:54 PM
Subject: Re: [ RadSafe ] Radiation in landfills


> NOTE : Not forwarded to RADSAFE, I've been informed that my posts are too 
> basic, not advanced enough. Sorry about that. George
>
> Thanks Bob and John for the insight. I had been thinking that the foil 
> left the H3 exposed because of the  large
> doserate (relatively) out the front of the instrument using a thin window 
> pancake.
>
> So, first I tried bending the betas in the New London Bendatron (magnetic 
> beta spectrometer*) and sure enough, the radiation did not bend at all.
> Not a charged particle then.
>
> Usually the Bendatron will easily deflect betas 90 degrees (one way) and 
> positrons ( the other way).
> Does anyone have the stats on the H3 Brems? I assume they range up to 18 
> keV only, with the peak around 5.6 keV ( the beta E-Max and E-Av for H3).
> These levels could easily be detected and plotted using an HPGE, but a 
> metal housed NaI(Tl) would be way beyond the lower limit of its range, 
> energy wise. **
>
> A quick HVL test showed that the from a model 702 radiation will be 50% 
> blocked by a 2.3 mg/cm>2 absorber***. On the same jig, a
> Fe-55 sample with ~6 keV gammas showed similar HVL.
>
> Now it makes perfect sense why we can see some form of radiation from 
> those exit signs. It is electromagnetic, not beta particles. Whatever
> the statistical attenuation of the glass enclosure is, it  will allow some 
> measure of the Brems to get out and be detectable in a suitable sensor.
>
>
> * I also use the Bendatron to separate betas from a beta-gamma emitter, 
> for individual analysis.
> ** Nada on my 3" X 3" Bicron NaI(Tl) in the Gamma spec.It stops at about 
> 20 keV.
> *** actually it is a bit less than 2.3mg/cm>2, but that is the thinnest 
> calibrated absorber I have. Air has a density of 0.001293 gm/cm (HP 
> Handbook)
>
> George Dowell
> NLNL
> New London Nucleonics Lab
> 573-221-3418
> GEOelectronics at netscape.com
>
>
> ---- Original Message ----- 
> From: "Geo>K0FF" <GEOelectronics at netscape.com>
> To: "Robert D Gallagher" <rdgallagher at nssihouston.com>; "John R Johnson" 
> <idias at interchange.ubc.ca>; "Brennan, Mike (DOH)" 
> <Mike.Brennan at DOH.WA.GOV>; <radsafe at radlab.nl>
> Sent: Tuesday, July 17, 2007 3:41 PM
> Subject: Re: [ RadSafe ] Radiation in landfills
>
>
>>
>> ----- Original Message ----- 
>> From: "Robert D Gallagher" <rdgallagher at nssihouston.com>
>>
>>
>>
>>> The 3M foils used in the static devices I believe are
>>> Titanium as the Tritium comes off at the lower temperatures. We remove 
>>> the
>>> Tritium from these foils for reuse.
>>>
>>> Bob Gallagher
>>> >
>>> One would not normally expect any dose from Tritium from a foil. Usually 
>>> one
>>> can determine which side of the foil the Tritium is on by noting the 
>>> color
>>> of the metal. When in doubt, simply hold the foil up next to a pancake
>>> detector. The Bremstrahlung is easily measured.
>>>
>>> -----Original Message-----
>>> From: John R Johnson [mailto:idias at interchange.ubc.ca]
>>> >
>>> Radsafers
>>>
>>> Internal Bremsstrahlung accounts for 1/137 of the decay of tritium. It 
>>> does
>>> not result from the emission of beta rays. See page 617 of Robley Evan's
>>> book "The Atomic Nucleus" (McGraw-Hill, 1955).
>>>
>>> John
>>
>
>