[ RadSafe ] Beta emitters and external risks

[John Jacobus]

Elisa,
However, what if the radionuclide is at some distance
from the person and not on the skin?  Beta emissions
of 100 keV can penetrate about 6 inches of air, while
maximum P-32 beta particles can penetrate about 280
inches of air.  It would appear that P-32 betas would
have more than enough energy to penetrate air and
still deposit a dose.  

How far away from the Kr-85 source were beta burns
observed?  What was the activity? My estimate is the
the 700 keV beta particles of unshielded Kr-85 is 70
inches in air.

--- Elsa nimmo <Elsa.nimmo at varian.com> wrote:

> John,
> 
> For external risk & beta-emitters, it seems like one
> needs to be
> concerned with nuclides emitting betas energetic
> enough to penetrate to
> the live layer of skin -- energetic enough to
> penetrate at least 7
> mg/sq-cm.  So pure beta-emitters with an Emax < 70
> keV just aren't going
> to be of concern as an external radiation source. 
> 
> One application I worked with for some years used
> pressurized Kr-85 in
> thin-windowed sealed sources.  The Kr-85 betas
> emitted by the sources
> aren't penetrating enough to damage lens of the eye
> or anyone's internal
> organs, but they can cause skin burns depending on
> the sealed source
> design, Kr-85 content, & the exposure time &
> distance.
> 
> Anyway, for beta emitters with an Emax above
> something like 70 keV,
> seems like you have to assess the situation case by
> case, considering
> possible dose from betas capable of reaching live
> layer of skin....
> 
> Regards,
> Elsa Nimmo
> 
>  
> 
> > >> ----- Original Message ----- 
> > >> From: "John Jacobus" <crispy_bird at yahoo.com>
> > >> To: "radsafe" <radsafe at radlab.nl>
> > >> Sent: Friday, October 14, 2005 4:42 PM
> > >> Subject: [ RadSafe ] Beta emitters and external
> > > risks
> > >>
> > >>
> > >> > Question:  Would you say that beta emitters
> > pose
> > > an
> > >> > external radiation hazard or risk?  I am not
> > > consider
> > >> > skin contamination.
> > >> >
> > >> > Are there any (other) beta emitters that you
> > would
> > >> > consider to be a significant external hazard?
> > >> >
> > >> > What is your criteria for this judgement?
> > >> >
> > >> > (Background:  I would in a medical research
> > > facility,
> > >> > and we require beta shields for work
> involving
> > > large,
> > >> > e.g., 10 mCi/370 MBq, amounts of P-32.  Are
> > there
> > >> > other beta emitters we should worry about?)
> > >> >
> > >> > +++++++++++++++++++
> > >> > On Oct. 5, 1947, in the first televised White
> > > House address, President
> > >> > Truman asked Americans to refrain from eating
> > meat
> > > on Tuesdays and poultry
> > >> > on Thursdays to help stockpile grain for
> > starving
> > > people in Europe.
> > >> >
> > >> > -- John
> > >> > John Jacobus, MS
> > >> > Certified Health Physicist
> > >> > e-mail:  crispy_bird at yahoo.com
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+++++++++++++++++++
On Oct. 5, 1947, in the first televised White House address, President Truman asked Americans to refrain from eating meat on Tuesdays and poultry on Thursdays to help stockpile grain for starving people in Europe. 

-- John
John Jacobus, MS
Certified Health Physicist
e-mail:  crispy_bird at yahoo.com


	
		
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