photon homogenized cross sections

Separate section for discussion on gamma transport
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nico
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photon homogenized cross sections

Post by nico » Thu Oct 03, 2019 5:37 pm

Dear Serpent developers,
I would like to use Serpent in order to generate, in addition to the neutron group constants, also a set of group constants for photons, in order to use them as input data for a deterministic code that couples neutron and photon transport to thermal-hydraulics (the code is named Frenetic and should be employed for the analysis of liquid metal fast reactors).

I tried to define some detectors, however I cannot figure out how to get the photon scattering matrix. Frenetic requires total cross section (det dr -25 for photons), absorption cross section (there is no something similar in macroscopic reaction numbers, so I thought to use nuclide-wise MTs and then to multiply for the nuclear density of each nuclide in the detector spatial bin and finally sum everything up) and scattering matrix.

What should I do in order to get the multi-group scattering matrix (and eventually even the absorption cross section, maybe in an easier way)?

Thank you for your attention,
Have a nice day
Nicolo'

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Jaakko Leppänen
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Re: photon homogenized cross sections

Post by Jaakko Leppänen » Sat Oct 05, 2019 10:57 am

The neutron scattering matrices are calculated by built-in analog estimators, and unfortunately there is no detector capability to accomplish the same task (for neutrons or photons).
- Jaakko

nico
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Re: photon homogenized cross sections

Post by nico » Tue Oct 08, 2019 10:08 am

Dear Jaakko,

thanks for your answer. I would have another question regarding coupled neutron-photon transport.
Since I cannot find the scattering matrices for photons, I would be happy even with one-group cross sections for photons (better than nothing, in my case), however, when I try to run the simulation, an error about memory allocation comes out.
Looking at the RAM requirements:
1) 100k neutrons with "set ngamma 1" and requires 42% of the RAM (i.e. 42 GB)
2) 100k neutrons with "set ngamma 0" and requires 42% of the RAM (i.e. 42 GB), photon data are loaded but only neutron transport is performed
3) 100k neutrons without photons (commenting the line "set ngamma 1") only 2.8% (almost 3 GB), no photons data and no photon transport

Why is there such a memory requirements? I'd need to run simulations with 1M neutrons, so I wonder if there is a way to fix this issue.

I attach the code here,

Code: Select all

%% -- EXTERNAL FILE INCLUSION
include "/home/pclab/serpent2models/alfred/materials/ALFRED_materials_673_673"  % materials
include "/home/pclab/serpent2models/alfred/geometry/ALFRED_geometry"            % geometry

%% -- LIBRARY FOR NUCLEAR DATA
set acelib "/opt/serpent/xsdata/endfb7/sss_endfb7.xsdata"
set pdatadir "/opt/serpent/xsdata/photon_data"

%% --------------------------------------------- Core lattice loading ---------------------------------------------
% Core
surf s1 sqc 0.0 0.0 25	      % wrapping inner perimeter

lat core 3 0.0 0.0 5 5 17.1      % Core with CR and SR extracted
ifa ifa ifa ifa ifa
 ifa ifa ifa ifa ifa
  ifa ifa ifa ifa ifa
   ifa ifa ifa ifa ifa
    ifa ifa ifa ifa ifa

%% --------------------------------------------------------------------------------------------------------------------------------

cell c100 0 fill core -s1  % Filling the cylinder with the core
cell c101 0 outside s1     % Placing the vacuum outside the reactor


%% -- SIMULATION SETUP
set bc 2
set pop 100000 500 50

set power 1              % fix power to 1 W
set ures 1               % sample fast unresolved resonance region (urr)
set his yes              % Check on fission source convergence
set ngamma 1             % set coupled neutron-photon calculation


det pprod n dm fueli de mygrid dr -5   void % photons source
det psrc  p dm fueli de mygrid dr -11  void 
det ptot  p du ifa             dr -25  void % total macroscopic XS for photons
Thank you,
Nicolo'

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