Dear all
I am trying to design a neutron shield around a neutron beamport in a nuclear reactor. The shielding consists of collimator (placed inside the beamport) and outer shielding. I have split the simulation in two parts. In the first part, I transport the neutrons from inside of the beamport to just outside. The neutrons exiting the beamport are recorded using the mgdraw.f. Then in the second step, I use the source_newgen.f to read the file recorded in the first step and transport the neutrons (as recorded by mgdraw.f in the first step) further. The usual standard two step procedure.
The problem I am facing is that I see lot of error in the err file. All the problem seem to be around ~ z=0. If I move the cylRKTR1 (the cylinder representing the reactor biological shield) backwards (towards neg z) by say 1 cm, all the errors are gone.
can some one please help out in pointing what is the problem?
The 1st step files are here- neutron_shield_1stStep.inp (26.6 KB) mgdraw.f (10.1 KB)
). The output of the 1st step is- neutron_flux_collim_exit_280mm.zip (1.3 MB)
. The files for second step are- neutron_shield_2ndStep.inp (27.1 KB) source_newgen_neutron_collExit_coll_ID280mm.f (18.9 KB). THe error file is - neutron_shield_2ndStep001.err (1.5 MB)
the problem is that you are starting the particles on a boundary. To mitigate the issue, you nudge the them with an infinitesimal step along their direction when you load them into the FLUKA stack during the second step.
Two other comments:
You may want to activate the point-wise cross sections for low energy neutrons for a more accurate simulation.
In your mgdraw routine, you are saving the energy of the primary particle, not the actual energy of the crossing one. I don’t know if this is something you want to do or not.
Dear David
Thanks for the reply! About your comments, I will include the LOW-NEUT card to activate the point-wise cross sections for low energy neutron. About saving the KE of the particle when it crosses the boundary, how to do that?
sincerely
saurabh
to activate the point-wise cross sections you need to use the LOW-PWXS card.
You can calculate the kinetic energy if the particle with ETRACK - AM(JTRACK) (Total energy minus the rest).
Just to keep in mind: If you are using the default group-wise cross sections for low energy neutrons, then their energy won’t be continuous, they will all have the discreet energies of the groups assigned to them.