RE: USRBIN-Neutron Balance Density

Dear Guojun Hu,

Yes for bins overlapping region with fissile material the neutron balance is likely to be positive while for areas with shielding or
reflector material it should be zero or negative. If you consider for example one neutron entering a bin, inducing a fission leading
to 3 neutrons. If 1 of the 3 neutron is captured and the 2 others escape the bin then the neutron balance de=
nsity is 1 (considering the bin volume is equal to unity).
Besides fissions, any y,xn reaction leading to neutrons (spallation if energy sufficient) will also lead to a positive gain if the
produced neutrons make it out of the considered bin.

Regards
Joachim

-----Original Message-----
From: owner-fluka-discuss_at_mi.infn.it [mailto:owner-fluka-discuss_at_mi.infn.it=
] On Behalf Of huguojun_at_mail.ustc.edu.cn
Sent: 21 July 2012 08:22
To: fluka-discuss_at_fluka.org
Subject: USRBIN-Neutron Balance Density

Dear FLUKA experts,
       I have a problem about Neutron Balance Density in USRBIN detector. In the handbook of fluka, neutron balance density is an
"algebraic sum of outgoing neutrons minus incoming neutrons for all interactions". For a particular bin(such as x[x1,x2],y[y1,y2],
z[z1,z2] in a X-Y-Z coordinate system ) in a multiplying system which is in an unsteady state, sum of outgoing neut=
rons minus incoming neutrons may be positive, is this sum the number of neutrons produced (such as produced by fission)in this bin ?
       Thanks in advance!
       Guojun Hu
Received on Sun Jul 22 2012 - 13:06:09 CEST