[ RadSafe ] Re:[RadSafe] Linac Shield calculation/NCRP 151 and others..

[JPreisig at aol.com]

Hi Radsafers and Mark Ramsay,

     This is from:    jpreisig at aol.com   .

     Hope all is well at your various jobs and facilities around the world.
Linac shield calculation.  I've seen NCRP 51, but haven't seen NCRP 151 yet.
Hope it is very useful.  I don't do medical linac stuff much.  For good 
accelerator health physics fundamental information, please refer to 
Accelerator
Health Physics by Paterson and Thomas and the HP course book by
Cossairt.

     I see you are doing a direct mathematical hand calculation.  Good.
MCNP and/or MCNPX can do gamma/photon calculations and some electron
calculations.  Don't know if these computer codes are useful for this
situation.  EGS <Electron Gamma Shower> is a computer code for doing
problems like the one you are doing.  I don't know the energy range for this
computer codes applicability.  EGS is available from Canada's NRC <look 
for it via the internet> and/or SLAC <Stanford Linear Accelerator Center>.

     Fundamentally, rocket science is physics!!!!

     Would it be useful to have a layer of high Z material on the inner 
surface 
of your shield wall????  Brookhaven tends to use iron shield blocks
and concrete at the Alternating Gradient Synchrotron <AGS>, but of course,
this is a higher energy protron accelerator.

     Do your ion chambers under- or over-respond in the electron/photon
energy range of interest???  Find out...

     On a non-related topic from radsafe past, there was some interest
in TLD's, badge boards and the like.  Nothing much stops the Health 
Physicist
at a well run facility from getting a MultiChannel Analyzer <portable 
version>
with a gamma/photon scintillator probe and making direct energy spectrum
measurements at each badge board during typical rad source operating
conditions.  Then account for what percentage of time during a given month
the badge board receives dose/exposure.  One can also do neutron 
studies at a badge board using a Snoopy, Anderson-Braun detector, some
newfangled neutron meter, and the like.  Health Physicists with time, money 
and
a Bonner Multisphere Spectrometer <polyethylene spheres, etc.> could 
actually make neutron spectrum measurements at each badge board.
Information on Bonner Spectrometry is available in Patterson and Thomas,
Coissairt/Cossairt, the Radsafe Archives!!! and possibly on the internet.

     Mark Ramsay, I hope you can find a good answer to your shielding
problem.  Now that I've written this e-mail, I'm sure that one of my bright
Health Physics colleagues who post on Radsafe will give you a simple answer
to your e-mail.

     For an HP out there who wants a job at Brookhaven <I no longer work
there> in radiation physics/radiation chemistry <actually creation of
unique radiation sources for scientific purposes by proton bombardment, I
think???> please see Brookhaven's employment web-site.

     Hope you all are having a great day/week!!!!


     Regards,     Joseph R. <Joe> Preisig,  Ph.D.



<BR><BR>**************<BR>Make your summer sizzle with fast and easy recipes for the 
grill. (http://food.aol.com/grilling?ncid=emlcntusfood00000005)</HTML>