Pulsated Neutron Test - Question about Scoring Efficiency

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MojoJojo
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Pulsated Neutron Test - Question about Scoring Efficiency

Post by MojoJojo » Sun Apr 19, 2020 3:00 am

NOTE: Scroll down to "Now my question! " if you are not interested in all this blabbing.
Hello everyone,

I'm performing a pulsated neutron test using a Deuterium-Deuterium fusion-based neutron generator (DD). I modified the usersrc.c subroutine in order to define the energy and relative yield angular dependencies of the DD point source (that's not very important for my question). See usersrc.c and the src6.txt (contains source definition, mentioned in the Serpent input code as 'include ./SRC_DEF/src6.txt) in the links below:
https://drive.google.com/file/d/1Lo9USu ... sp=sharing
https://drive.google.com/file/d/1nlNVj5 ... sp=sharing

Summary of the input code:
1- Molten salt subcritical experiment (See pictures)
Image
Image
2- 50 pulses per second (pulse width 2 micro second)
3- Running the reactor for 410 seconds in order to accumulate a total of 20000 pulses (pulses in the first 10 seconds are neglected).
4- Detector time binning: starting at 10 seconds and ending at 410 seconds.
5- Delayed neutrons are enabled (set delnu 1)
6- 1000,000,000 total number of histories, 10000 batches (100000 histories per batch).
7- Thermal scattering data of Berylium metal is used in the fuel salt
7- Goal: Compute the delayed neutron fraction (beta) and the prompt generation time (Lambda) from cumulated pulse profiles using Sjöstrand Method and the Slope Fit Method (check paper for more information about the methods: https://drive.google.com/file/d/1RBeeEJ ... sp=sharing)

Now my question!

I'm interested in delayed neutrons accumulation in the He-3 detector, and I was wondering if you could provide me with any tips to improve scoring efficiency. I found the following input cards in SerpentWiki, but I'm not sure if they would be useful.

Code: Select all

set precthresh THRESHOLD
I was thinking I would reduce the threshold to 0.0001 so that most precursers would score above the threshold.

Code: Select all

set precsrcf FACTOR
I was thinking to increase the number of point-wise precursors from 10 to 100 to increase scoring efficiency


The Serpent input code:

Code: Select all

%-------------------------------------------------------------------------------------------------
% Code Title
%-------------------------------------------------------------------------------------------------
set title "Subcritical Pile with DD Source"

%-------------------------------------------------------------------------------------------------
% Neutron Cross-section library
%-------------------------------------------------------------------------------------------------
set acelib "/home/moe235/jeff311/sss_jeff311u.xsdata"

%-------------------------------------------------------------------------------------------------
% Materials
%-------------------------------------------------------------------------------------------------
%%% Graphite
mat GraphT750 -1.80
tmp 750.00
moder graphT750 6000
rgb 75 75 75
C-nat.06c 99.999998
B-10.06c 0.0000004
B-11.06c 0.0000016
therm graphT750 750.0 grj3.16t grj3.18t

%%% Fuel salt
mat SaltT750 0.06659334 moder saltT750 4009 tmp 750 rgb 255 255 0
Be-9.06c   0.14020000
F-19.06c   1.55690000
Na-23.06c  0.72090000
U-234.06c  0.00004240
U-235.06c  0.00492148
U-238.06c  0.13393612
therm saltT750 750 be04.32t be05.32t

%%% SS @ 300 K
mat SST300 -8.027
rgb 112 128 144
Ni-nat.03c -0.100
C-nat.03c  -0.0003
Fe-nat.03c -0.67895
Cr-nat.03c -0.19
Ti-nat.03c -0.002
Si-nat.03c -0.01
S-nat.03c  -0.0003  

%%% SS @ 750 K
mat SST750 -8.027
tmp 750.0
rgb 112 128 144
Ni-nat.06c -0.100
C-nat.06c  -0.0003
Fe-nat.06c -0.67895
Cr-nat.06c -0.19
Ti-nat.06c -0.002
Si-nat.06c -0.01
S-nat.06c  -0.0003 

%%% Argon Cover Gas
mat Argon -0.0016238
rgb 128 0 128
Ar-36.06c  0.334
Ar-38.06c  0.063
Ar-40.06c  99.604

%%% Helium-3 - Detector#1
mat He3_1 -0.0016283
rgb 255 140 0
He-3.06c -1.00000000

%%% Helium-3 - Detector#3
mat He3_3 -0.0016283
rgb 255 140 0
He-3.06c -1.00000000

%%% Helium-3 - Detector#4
mat He3_4 -0.0016283
rgb 255 140 0
He-3.06c -1.00000000

%%% Helium-3 - Detector#6
mat He3_6 -0.0016283
rgb 255 140 0
He-3.06c -1.00000000

%%% Helium-3 - Detector#7
mat He3_7 -0.0016283
rgb 255 140 0
He-3.06c -1.00000000

%%% Helium-3 - Detector#9
mat He3_9 -0.0016283
rgb 255 140 0
He-3.06c -1.00000000

%%% Helium-3 - Detector#10
mat He3_10 -0.0016283
rgb 255 140 0
He-3.06c -1.00000000

%%% Helium-3 - Detector#12
mat He3_12 -0.0016283
rgb 255 140 0
He-3.06c -1.00000000

%-------------------------------------------------------------------------------------------------
% Latices
%-------------------------------------------------------------------------------------------------
%% Fuel Channels
%%% Filled (universe #1)
surf A cyl    0.0 0.0 2.000
surf B hexyc  0.0 0.0 8.200
cell A 1 SaltT750  -A
cell B 1 GraphT750  A -B

%%% just Graphite (universe #2)
surf C hexyc  0.0 0.0 8.200
cell C 2 GraphT750 -C

%%% Hexagonal lattice of fueled channels: 77 channels, pitch = 14cm (universe #4)
lat 3 3 0 0 15 17 16.4
2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
  2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
   2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
    2 2 2 2 2 2 2 2 1 1 1 2 2 2 2
     2 2 2 2 2 2 1 1 1 1 1 1 2 2 2
      2 2 2 2 2 1 1 1 1 1 1 1 2 2 2
       2 2 2 2 1 1 1 1 1 1 1 1 2 2 2
        2 2 2 2 1 1 1 2 1 1 1 2 2 2 2
         2 2 2 1 1 1 1 1 1 1 1 2 2 2 2
          2 2 2 1 1 1 1 1 1 1 2 2 2 2 2
           2 2 2 1 1 1 1 1 1 2 2 2 2 2 2
            2 2 2 2 1 1 1 2 2 2 2 2 2 2 2
             2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
              2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
               2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
                2 2 2 2 2 2 2 2 2 2 2 2 2 2 2

%% Measuring Channels
%%% Thimble (universe #6)
pin 4
Argon      2.000
GraphT750

%%% Just Graphite (universe #7)
pin 5
GraphT750

%%% Circular lattice of empty thimbles (universe #8)
lat 6 4 0.0 0.0 2
1 0.000 0.000 5
8 72.50 180.0 4 4 4 4 5 5 5 5

%-------------------------------------------------------------------------------------------------
% Surfaces 
%-------------------------------------------------------------------------------------------------
%%% Core === Planes                       %Under               < Above
surf C10 pz   0.00000000                  %Outside             < External Coating
surf C11 pz   0.50000000                  %External Coating    < Bottom Reflector
surf C12 pz   30.5000000                  %Bottom Reflector    < Active Core
surf C14 pz   240.500000                  %Active Core         < Top Reflector
surf C15 pz   280.500000                  %Top Reflector       < External Coating
surf C16 pz   281.000000                  %External Coating    < Outside

%%% Core === Infinite Cylinders             %Inward              < Outward
surf C17 cyl  0.00000000  0.00000  70.00000 %Active Core         < Side Reflector
surf C18 cyl  0.00000000  0.00000  95.00000 %Side Reflector      < Coating
surf C19 cyl  0.00000000  0.00000  95.50000 %Coating             < Outside

%%% Core === Finite Cylinders
surf C20 cyl  0.00000000  0.00000  95.50000  0.000000  281.0000 %Dummy cylinder
surf C21 cyl  0.00000000  0.00000  4.000000  135.0000  281.0000 %Beam Cavity

%%% Detectors === Infinite Cylinders
%%%% Thimble 1
surf D10 cyl -72.5000000  0.000000  0.635000  31.05000  55.94200 %Bottom Detector He-3 Gas
surf D11 cyl -72.5000000  0.000000  0.640000  31.00000  55.99200 %Bottom Detector Gas Chamber
surf D14 cyl -72.5000000  0.000000  0.635000  215.0580  239.9500 %Top Detector He-3 Gas
surf D15 cyl -72.5000000  0.000000  0.640000  215.0080  240.0000 %Top Detector Gas Chamber

%%%% Thimble 2
surf D16 cyl -51.2652400 -51.26524  0.635000  31.05000  55.94200 %Bottom Detector He-3 Gas
surf D17 cyl -51.2652400 -51.26524  0.640000  31.00000  55.99200 %Bottom Detector Gas Chamber
surf D20 cyl -51.2652400 -51.26524  0.635000  215.0580  239.9500 %Top Detector He-3 Gas
surf D21 cyl -51.2652400 -51.26524  0.640000  215.0080  240.0000 %Top Detector Gas Chamber

%%%% Thimble 3
surf D22 cyl  0.00000000 -72.50000  0.635000  31.05000  55.94200 %Bottom Detector He-3 Gas
surf D23 cyl  0.00000000 -72.50000  0.640000  31.00000  55.99200 %Bottom Detector Gas Chamber
surf D26 cyl  0.00000000 -72.50000  0.635000  215.0580  239.9500 %Top Detector He-3 Gas
surf D27 cyl  0.00000000 -72.50000  0.640000  215.0080  240.0000 %Top Detector Gas Chamber

%%%% Thimble 4
surf D28 cyl  51.2652400 -51.26524  0.635000  31.05000  55.94200 %Bottom Detector He-3 Gas
surf D29 cyl  51.2652400 -51.26524  0.640000  31.00000  55.99200 %Bottom Detector Gas Chamber
surf D32 cyl  51.2652400 -51.26524  0.635000  215.0580  239.9500 %Top Detector He-3 Gas
surf D33 cyl  51.2652400 -51.26524  0.640000  215.0080  240.0000 %Top Detector Gas Chamber

%-------------------------------------------------------------------------------------------------
% Cells
%-------------------------------------------------------------------------------------------------
%%% SS Coating 
cell C10 0 SST750    C10 -C11      -C19      %Bottom SS Coating
cell C11 0 SST750    C11 -C15  C18 -C19      %Side SS Coating
cell C12 0 SST750    C15 -C16      -C19  C21 %Top SS Coating

%%% Reflectors
cell C13 0 GraphT750 C11 -C12      -C18      %Bottom Reflector
cell C14 0 fill 6    C12 -C14  C17 -C18  D11 D15 D17 D21 D23 D27 D29 D33
cell C15 0 fill 6    C14 -C15      -C18  C21 %Top Reflector

%%% Active Core
cell C16 0 fill 3    C12 -C14      -C17  C21 %Full Active Core

%%% Detectors
%%%% Thimble 1
cell D10 0 He3_1         -D10                %Bottom Detector He-3 Gas
cell D11 0 SST300    D10 -D11                %Bottom Detector Gas Chamber
cell D14 0 He3_3         -D14                %Top Detector He-3 Gas
cell D15 0 SST300    D14 -D15                %Top Detector Gas Chamber

%%%% Thimble 2
cell D16 0 He3_4         -D16                %Bottom Detector He-3 Gas
cell D17 0 SST300    D16 -D17                %Bottom Detector Gas Chamber
cell D20 0 He3_6         -D20                %Top Detector He-3 Gas
cell D21 0 SST300    D20 -D21                %Top Detector Gas Chamber

%%%% Thimble 3
cell D22 0 He3_7         -D22                %Bottom Detector He-3 Gas
cell D23 0 SST300    D22 -D23                %Bottom Detector Gas Chamber
cell D26 0 He3_9         -D26                %Top Detector He-3 Gas
cell D27 0 SST300    D26 -D27                %Top Detector Gas Chamber

%%%% Thimble 4
cell D28 0 He3_10        -D28                %Bottom Detector He-3 Gas
cell D29 0 SST300    D28 -D29                %Bottom Detector Gas Chamber
cell D32 0 He3_12        -D32                %Top Detector He-3 Gas
cell D33 0 SST300    D32 -D33                %Top Detector Gas Chamber

%%% Neutron Source
cell N10 0 Argon         -C21                %Source Cavity

%%% Outside
cell U12 0 outside   C20

%-------------------------------------------------------------------------------------------------
% Calculation Options
%-------------------------------------------------------------------------------------------------
%%% Black Boundry condition
set bc 1

%%% External Source Rate Normalization Option 
set srcrate 5.0E+10

%%% Enable emission of delayed neutrons
set delnu 1

%%% Time bin structure of neutron source emission (type 2: uniform binning)
tme srctime 2 1 0.000 410.0

%%% Time bin structure of detectors (type 1: arbitrary binning)
include "./SRC_DEF/tmedet6.txt"

%%% External Neutron Source Mode Enabled via nps input card
set nps 1000000000 10000 srctime

%%% External Neutron Source Definition
include "./SRC_DEF/src6.txt"

%-------------------------------------------------------------------------------------------------
% Energy Grids
%-------------------------------------------------------------------------------------------------
%%% 1 energy-group structre (Type 1 Grid Definition: Specify Energy Bin Boundries)
ene 1 1
1.000E-11 1.000E+01 

%-------------------------------------------------------------------------------------------------
% Detectors
%-------------------------------------------------------------------------------------------------
%%% Total fission energy deposition (unit: Watt)
det POWER  de 1 dr -8 void di dettime    

%%% Macroscopic total capture rate in Helium-3 Detector (unit: Rxn. cm-3.s-1) 
det He3_6  de 1 dr -2 He3_6  dm He3_6  dv 31.5324 di dettime       

%-------------------------------------------------------------------------------------------------
% Geometry and Mesh Plots 
%-------------------------------------------------------------------------------------------------
plot 1 500 735
plot 2 500 735
plot 3 500 500
mesh 1 500 735
mesh 2 500 735
mesh 3 500 500
Name: Mohammed Mahdi
Occupation: MASc. Student
Research Interest: Liquid Fuel Molten Salt Reactor
Institution: McMaster University
Email Address: Mahdim4@mcmaster.ca

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