Reflective boundary condition of neutron transport simulation in FLUKA

From: Alberto Fasso' <fasso_at_SLAC.Stanford.EDU>
Date: Sun, 8 Jul 2012 08:28:24 -0700 (PDT)

Dear Walker,

to simulate a reflective boundary, you need to write, compile and link a user
routine USRMED (you find a template in $FLUPRO/usermvax), which is activated
by a command MAT-PROP with SDUM = USERDIRE (look up MAT-PROP in the manual).
I copy here the description of USRMED from Chap. 13 of the manual:

Subroutine USRMED is activated by option MAT-PROP with SDUM = USERDIRE, for one
or more materials indicated by the user. It is called every time a particle is
going to be transported in one of the user-flagged materials. Two cases are
possible:

1) MREG = NEWREG: the particle is going to move from a point inside the medium.
The user is allowed to change only the particle weight. Typical application:
simulating attenuation of optical photons in an absorbing medium by reducing the
photon weight.
2) MREG not = NEWREG: the particle is going to move from a point on a boundary
between two different regions. The user may change any of the following:
particle weight, current region number, direction cosines. Typical applications:
* simulating refraction, by changing the direction cosines so that the particle is
   still inside the same region. To do this, one generally needs the direction
   cosines of the normal to the surface: TXNOR(NPFLKA), TYNOR(NPFLKA),
   TZNOR(NPFLKA) (COMMON FLKSTK must be included).
* simulating reflection (albedo) at a boundary. The direction cosines must be
    modified according to some reflection law or albedo angular distribution, and
    NEWREG must be set = MREG.
    In both cases the weight can also be reduced to account for surface reflectivity
    or similar

Alberto

> From: walker <wdx456_at_mail.ustc.edu.cn>
> Date: Tue, 3 Jul 2012 16:13:59 +0800
> Dear FLUKA experts and users,
> I've been carrying out a neutron transport simulation by FLUKA with
> reflective boundary.
> Is there such card in FLUKA that can be used to describe reflective
> conditions?
> Cheers,
> Walker
Received on Sun Jul 08 2012 - 19:19:05 CEST

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