Running gamma transport simulation

Separate section for discussion on gamma transport
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Jaakko Leppänen
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Running gamma transport simulation

Post by Jaakko Leppänen » Mon Feb 06, 2012 4:23 pm

Running a gamma transport simulation is very similar to an external source neutron transport simulation, with a few minor differences:

1) The calculation requires gamma-transport libraries. The data is not available in the Serpent 1 installation package, but any ACE-format gamma library should work.

2) Particle type must be set to photon in the source definition by adding "g", "p", "gamma" or "photon" after the source name:

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src <name> g ...
3) Detectors may not yet be fully compatible with gamma transport mode

You can expect a lot of errors and problems when running a gamma transport simulation, since the mode has not been extensively tested. Also note that the physics model is somewhat incomplete (I'll post something about that later).
- Jaakko

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markdehart
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Re: Running gamma transport simulation

Post by markdehart » Mon Sep 09, 2013 6:08 pm

Okay, I am interested in taking a look at Serpent's gamma transport capabilities. But what I really want to do is a coupled neutron-gamma calculation. While I realize that this option is not yet available, it seems to me that I ought to be able to do a neutron calculation, and use the fission locations as a gamma source. Is there a way to get a dump of the fission locations that I could turn around and convert to a gamma source?

Mark

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Re: Running gamma transport simulation

Post by Jaakko Leppänen » Tue Sep 10, 2013 9:38 am

See:

http://ttuki.vtt.fi/serpent/viewtopic.php?f=24&t=1826

The "set csw" option should give you a file with all fission neutrons. The file is in ascii, and has one source point per line with format:

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<x> <y> <z> <u> <v> <w> <E> <wgt> <t>
(coordinates, direction cosines, energy, weight and time). If you need the incident neutron data instead, you can set up a detector:

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det <name> dr -6 void df <file> <frac> 
that should give you fission rate over all fissile materials and write fraction "<frac>" of all neutrons that make the scores into file "<file>". The fraction parameter is not mentioned in the description above, and the reason to add it was to avoid getting excessively large source files if your calculation has also other purposes than generating them and you need to run a large number of neutron histories.

While generating the source file, the code writes the points into a memory buffer, and dumps it into a file when it gets full, so you may not see the files until the calculation is completed.
- Jaakko

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Re: Running gamma transport simulation

Post by markdehart » Fri Sep 13, 2013 6:13 pm

I've had mixed success with this endeavor.

I've been able to generate a source distribution to play with, and create a photon library to use that Serpent will read. The first problem I had was with xsdirconvert.pl. When it reads the mcnp xsdir file it seems to skip all photon data. All the neutron data went into the xsdata file, but no photons. I ended up manually creating a Serpent xsdata file. However, this may be the cause of my latest error. When I run the gamma case, I get the following:

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...

***** Warning:
 Photon interaction data not available for hafnium (Z = 72)


 ***** Warning:
 Photon interaction data not available for uranium (Z = 92)

Checking data and printing output...
OK.

Generating unionize energy grids...

Adding points:

GetImportantPts: i != itot.
The warning message is printed for all nuclides in the problem, and I suspect that this is the cause of the ultimate failure.

My xsdata file has data in the following format. Is something else needed here to tell Serpent that this is photon data?

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  1000.04p   1000.04p  1   1000  0    0.999242  294  0  /serpent/xsdata/mcnp_data/mcplib04
  2000.04p   2000.04p  1   2000  0    3.968220  294  0  /serpent/xsdata/mcnp_data/mcplib04
  3000.04p   3000.04p  1   3000  0    6.881380  294  0  /serpent/xsdata/mcnp_data/mcplib04 
  4000.04p   4000.04p  1   4000  0    8.934770  294  0  /serpent/xsdata/mcnp_data/mcplib04 
  5000.04p   5000.04p  1   5000  0   10.717100  294  0  /serpent/xsdata/mcnp_data/mcplib04 
  6000.04p   6000.04p  1   6000  0   11.907800  294  0  /serpent/xsdata/mcnp_data/mcplib04 
  7000.04p   7000.04p  1   7000  0   13.886400  294  0  /serpent/xsdata/mcnp_data/mcplib04 
  8000.04p   8000.04p  1   8000  0   15.862000  294  0  /serpent/xsdata/mcnp_data/mcplib04 
  9000.04p   9000.04p  1   9000  0   18.835200  294  0  /serpent/xsdata/mcnp_data/mcplib04 
 10000.04p  10000.04p  1  10000  0   20.005600  294  0  /serpent/xsdata/mcnp_data/mcplib04 
 11000.04p  11000.04p  1  11000  0   22.792300  294  0  /serpent/xsdata/mcnp_data/mcplib04 
...

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Jaakko Leppänen
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Re: Running gamma transport simulation

Post by Jaakko Leppänen » Thu Sep 19, 2013 6:58 pm

Sorry about the delayed reply to a simple question... The data type in column 3 must be changed from 1 to 5.
- Jaakko

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Re: Running gamma transport simulation

Post by markdehart » Thu Sep 19, 2013 10:23 pm

Okay, that moves me forward a bit, but the next error I have no clue on:

...
26000.04p -- Points added in photon grid: 122
27000.04p -- Points added in photon grid: 125
28000.04p -- Points added in photon grid: 124
29000.04p -- Points added in photon grid: 128
40000.04p -- Points added in photon grid: 182
72000.04p -- Points added in photon grid: 306
92000.04p -- Points added in photon grid: 287

Generating unionized energy grid:


***** Thu Sep 19 13:20:51 2013 (seed = 1379618447, MPI task = 0, OMP thread = 0)

Fatal error in function MakeEnergyGrid:

Values are not in ascending order

Simulation aborted.

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Re: Running gamma transport simulation

Post by Jaakko Leppänen » Sat Sep 21, 2013 1:54 am

I'm getting the same error. It looks like the problem has appeared sometime between updates 2.1.12 and 2.1.13. I'll look into it tomorrow.
- Jaakko

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Re: Running gamma transport simulation

Post by Jaakko Leppänen » Sat Sep 21, 2013 10:14 am

You need two fixes to get the gamma transport simulation going:

1) In unionizegrid.c, line 470, replace if-statement:

Code: Select all

 if (na > 0)
with:

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 if ((long)RDB[DATA_NEUTRON_TRANSPORT_MODE] == YES)
 
2) At the beginning of cachexs.c, add lines:

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 if ((long)RDB[DATA_NEUTRON_TRANSPORT_MODE] == NO)
   return;
- Jaakko

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Re: Running gamma transport simulation

Post by Jaakko Leppänen » Sat Sep 21, 2013 10:22 am

BTW, you can check your source by running the calculation with command line option "-tracks <N>". The code runs the first <N> source neutrons and plots their tracks in the geometry plots (or more precisely, the 2D projections of the tracks).
- Jaakko

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Re: Running gamma transport simulation

Post by markdehart » Sun Sep 22, 2013 6:01 am

This gets me into the iterations, but then it stops after just a couple of batches and tells me gbuf is too small. I bumped up gbuf to 100 and it told me it was limited to 10. I set it to 10 but then it again stops and tells me it needs to that it is too small.

I tried -tracks 1000 and that part ran, but no plots were generated.

Mark

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