Re: Skyshine from Burial Vaults

[JPreisig@AOL.COM]

Hmmmmm,



     This is from:     jpreisig@aol.com   .





      Hello Radsafers,



            MCNP4C is proven (i.e. tried and true) computer code for doing 

this

      type of work.  I don't think you have to benchmark it much (or at 

all???).

      What you have to do is make sure all your mcnp modelling assumptions

      are correct and accurate.  Then, with mcnp, you might want to make

      a series of mcnp runs with various thickness roofs on the vault.  You 

should

      have a tally (detector) at some distance above the center of the vault

      and a tally detector which looks at photon fluxes at some distance

      away from the center of the vault (i.e. the skyshine).  You might want

      to compare the results of a skyshine analytical model with the

      mcnp results.  Once your vault roof is thick enough to stop the photon

      radiation, then I don't think you have to make the roof too much 

thicker.



       MCNP is great stuff; the trouble with Monte Carlo work is you end up

       thinking in terms of probabilities (all the time --- kind of like 

being

       a junior Enrico Fermi???).  It's hard to give anyone a straight rad

       health answer (to an honest question), after having done Monte Carlo

       for a while.  Oh Well...



       Regards,               J.R. Preisig, Ph.D.