Unable to sample initial fission source

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daniel.cualbu
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Unable to sample initial fission source

Post by daniel.cualbu » Thu Feb 15, 2018 2:52 pm

Hi, when I try to run the program with this geometry
pin 1
AmBe 0.5
steel 1.5
air

pin 2
steel 1.5
air

pin 6
void 0.2
steel 1.5
air


%geometria tool

surf 1 pz 100 %testa
surf 2 pz 80 %testa det
surf 3 pz 79 %finedet
surf 4 pz -79 %testaAmBe
surf 5 pz -90 %fineAmBe
surf 6 pz -100 %fine


cell 1 3 air -6
cell 2 3 fill 2 6 -5
cell 3 3 fill 1 5 -4
cell 4 3 fill 2 4 -3
cell 5 3 fill 6 3 -2
cell 6 3 fill 2 2 -1
cell 7 3 air 1

the program says that is Unable to sample initial fission source, while when I run with this:
% --- Fuel part

pin 1
AmBe 0.5
steel 1.5
air

pin 2
steel 1.5
air

% --- fine tool

surf bottom1 pz -100

% --- inizio tool

surf top1 pz 100

% --- fine AmBe

surf bottom2 pz -90

% --- inizio AmBe

surf top2 pz -79

%definizione celle tool

cell 1 3 air -bottom1
cell 2 3 fill 2 bottom1 -bottom2
cell 3 3 fill 1 bottom2 -top2
cell 4 3 fill 2 top2 -top1
cell 5 3 air top1

the difference is just the in the head of the tool there is a cave with void inside, my idea is to fill it with the detector. But why doen't it work?

daniel.cualbu
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Re: Unable to sample initial fission source

Post by daniel.cualbu » Thu Feb 15, 2018 2:52 pm

while I run with the second geometry the program goes without any problems.

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Jaakko Leppänen
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Re: Unable to sample initial fission source

Post by Jaakko Leppänen » Thu Feb 15, 2018 6:34 pm

Could you please post the full inputs? I cannot reproduce the calculation with geometry data only.
- Jaakko

daniel.cualbu
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Re: Unable to sample initial fission source

Post by daniel.cualbu » Thu Feb 15, 2018 7:04 pm

yes, sure, thank you,
This doen't work:

%geometria roccia infinita


surf roccia inf

%geometria hole

surf hole cyl 0.000 0.000 6.0


%definizione celle universo 0

cell roccia 0 rock -roccia hole
cell fuori 0 outside roccia
cell hole 0 fill 3 -hole

%definizione materiali
mat air 1.225
7014.03c -0.7
8017.12c -0.3

mat rock 2.71
20000.06c -0.4
8017.06c -0.4
6000.09c -0.2

mat steel 7.5
6000.03c -0.04
26000.12c -0.96

mat AmBe sum
95241.03c -0.5
4007.03c -0.5

set pop 50000 50 20


det EnergyDetector de MyEnergyGrid dt -2 dc 2 du 3

ene MyEnergyGrid 3 500 1e-11 15e1
therm MyThermLib hwj3.00t

set acelib "/xs/sss_jeff311u.xsdata"


%definizione tool

% --- Fuel part

pin 1
AmBe 0.5
steel 1.5
air

pin 2
steel 1.5
air

pin 4
air 0.5
steel 1.5
air

% --- fine tool

surf bottom1 pz -100

% --- inizio tool

surf top1 pz 100

% --- fine AmBe

surf bottom2 pz -1

% --- inizio AmBe

surf top2 pz 1.0

%detector
surf topdet pz 85
surf botdet pz 86

%definizione celle tool

cell 1 3 air -bottom1
cell 2 3 fill 2 bottom1 -bottom2
cell 3 3 fill 1 bottom2 -top2
cell 4 3 fill 2 top2 -botdet
cell 7 3 fill 4 botdet -topdet
cell 8 3 fill 2 topdet -top1
cell 5 3 air top1

---------------------------------
instead this is (in comparison there is just a void part within the steel):

%geometria roccia infinita


surf roccia inf

%geometria hole

surf hole cyl 0.000 0.000 6.0


%definizione celle universo 0

cell roccia 0 rock -roccia hole
cell fuori 0 outside roccia
cell hole 0 fill 3 -hole

%definizione materiali
mat air 0.001225
7014.03c -0.7 %N
8017.12c -0.3 %O

mat rock 2.71
20000.06c -0.4 %Ca
8016.03c -0.4 %O
6000.09c -0.2 %C

mat steel 7.5
6000.03c -0.04 %C
26000.12c -0.96 %Fe

mat AmBe sum
95241.03c -0.5 %Am
4007.03c -0.5 %Be

mat mud 1.380
1001.03c -0.072 %H
6000.03c -0.0023 %C
8016.03c -0.66 %O
11022.03c -0.0019 %Na
13027.03c -0.0053 %Al
14000.03c -0.0069 %Si
16000.03c -0.0376 %S
17000.03c -0.0102 %Cl
19000.03c -0.0428 %K
56130.03c -0.1609 %Ba

mat water 1.0
1001.06c -0.11 %H
8016.06c -0.88 %O


set pop 50000 50 20


det EnergyDetector de MyEnergyGrid

ene MyEnergyGrid 3 500 1e-11 2e1
therm MyThermLib hwj3.00t

set acelib "/xs/sss_jeff311u.xsdata"


%definizione tool

% --- Fuel part

pin 1
AmBe 0.5
steel 1.5
air

pin 2
steel 1.5
air

% --- fine tool

surf bottom1 pz -100

% --- inizio tool

surf top1 pz 100

% --- fine AmBe

surf bottom2 pz -1

% --- inizio AmBe

surf top2 pz 1.0

%definizione celle tool

cell 1 3 air -bottom1
cell 2 3 fill 2 bottom1 -bottom2
cell 3 3 fill 1 bottom2 -top2
cell 4 3 fill 2 top2 -top1
cell 5 3 air top1

Then, another question if is possible, if I want to score each neutron caputerd in the void (means in the cave that I create within the steel) is the definition of the detector correct?
Thank you again

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Jaakko Leppänen
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Re: Unable to sample initial fission source

Post by Jaakko Leppänen » Fri Feb 16, 2018 7:31 pm

You are running the calculation in criticality source mode, which means that you are essentially simulating a self-sustaining chain reaction in the AmBe part of your geometry. This doesn't look like a reactor geometry, though. If you want to run an external source simulation, you'll need to define the source distribution (see Chapter 9 in Serpent manual).
- Jaakko

daniel.cualbu
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Re: Unable to sample initial fission source

Post by daniel.cualbu » Fri Feb 16, 2018 8:25 pm

Jaakko, thank you,

yes is not a reactor is just a steel probe of 2 meters and 2 cm of diameter with a He3 chamber as detector in the top (40 cm from the top) and a neutron source in the bottom (40cm from the bottom) which is done with AmBe. The probe is inside a hole fill with a certain mud, the hole is ideally infinite in z axis, and the hole is within a rock volume (the earth crust). My issue is simulate fast neutron produced by AmBe, their collision with the media, Mud-rock-steel, then count them in the detector as total capture. the technology that I'm trying to simulate Is a neutron log for porosity measurement useful in geophysics.
Do you understand what i wrote?

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Jaakko Leppänen
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Re: Unable to sample initial fission source

Post by Jaakko Leppänen » Sat Feb 17, 2018 3:48 pm

Yes, I understand. The problem is that even if you could get the criticality source simulation running, you wouldn't get the correct result. You need to run the calculation in external source mode and define the source distribution explicitly.
- Jaakko

daniel.cualbu
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Re: Unable to sample initial fission source

Post by daniel.cualbu » Sun Feb 18, 2018 8:57 pm

Jaakko thank you, ok but what do you think obout the detector? Shoul I define a volume with inside He3 within the steel tool and than put that volume into the parameters of the detector or something else?

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