[fluka-discuss]: Clarification on neutron yield

From: Alberto Fasso' <fasso_at_slac.stanford.edu>
Date: Fri, 23 May 2014 02:26:03 -0700 (PDT)

Dear Francesca,

first of all, in your input some material names (238UOx, BUTYL) are not aligned
on column 71, and the program certainly assumes that their name begins with one
or two blanks. Thus, the LAM-BIAS command fails to associate the name you give
with that of a material assigned to a region.

In addition, when using LAM-BIAS to bias the inelastic interaction length, you
have only a choice between one material or all materials. You cannot ask for
two materials. You have issued two LAM-BIAS cards: the first is associated with
238-U, which is not assigned to any region, although it is used to define the
compound 238UOx. Then you have issued a second LAM-BIAS card for 238UOx, which
I guess must be ignored, since you have already requested one (useless) for 238-U.

Summarizing:
- adjust the alignment in the MATERIAL definition of 238-U and BUTYL
- remove the LAMB-BIAS card for 238-U and leave only that for 238UOx.

I would like to add a little piece of advice on a different issue. Calling all
bodies B53, B72, etc., and all the regions A017, A023 etc., is not a very smart thing.
It is not wrong, of course, but it does not take advantage of the huge effort
which has been made by the FLUKA developers to allow the users to use mnemonic
names. In your case (118 bodies and 104 regions) it is really hard to remember
what is what (I tried to identify the 238UOx region, and I gave up). In
addition, if you want to add or remove one body, you either re-number all of them,
or get even more confused. I admit that this was the way we all worked in a far
past, before the names were introduced: but now we can avoid it, especially if
there is a large number of bodies and regions.

Alberto


From: <francesca.belloni_at_libero.it>
Date: Thu, 22 May 2014 11:32:03 +0200 (CEST)

Dear all,
         I am trying to score fissions in (8-U)oxyde, to "confirm" results by
another code.
But when I run the FLUKA simulation for this problem, the result of
SCORE FISSIONS HE-FISS LE-FISS
is 0.0 0.0 0.0 respectively.

       The incident neutrons have a kinetic energy of 1 MeV and are
isotropically emitted.
The 238U oxyde layers are really thin, therefore I added 2 LAM-BIAS cards (one
for 8-U and one
for (8-U)oxyde. By the way...is it fine putting a LAM-BIAS in both materials
or by using only
a LAM-BIAS card associated to U8 would have been enough, please?)

      Did I forget something, please?


Thank you and best regards,
Francesca
Received on Fri May 23 2014 - 12:41:55 CEST