Hafnium Metastable

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jesse.johns
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Joined: Wed Apr 20, 2011 5:19 am

Hafnium Metastable

Post by jesse.johns » Sat Feb 18, 2017 8:44 pm

Hello,

I'm running some depletion/activation calculations on a hafnium target, and I'm noticing that at least Hf-179m is a few orders of magnitude these than expected. Also, once I added in metastable cross-sections - the the isomeric flag, etc, the depletion routine lost track of the metastables completely. Beyond modifying the ACE and XSDATA files, what other considerations do I need to make to improve the depletion routine for these metastable states?

I can provide a sample input, my xsdata addtions on request.

Thank you,

Jesse

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Jaakko Leppänen
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Re: Hafnium Metastable

Post by Jaakko Leppänen » Sun Feb 19, 2017 9:09 pm

The default branching ratio for Hf-179 neutron capture is 99.1% to the ground state. Serpent 2 has an option to change the default values:

http://serpent.vtt.fi/mediawiki/index.p ... set_isobra

What do you mean that the depletion routine lost track completely? Do you get zero concentrations or is the nuclide missing completely in the .out output file?
- Jaakko

jesse.johns
Posts: 114
Joined: Wed Apr 20, 2011 5:19 am

Re: Hafnium Metastable

Post by jesse.johns » Mon Feb 20, 2017 7:17 pm

Hi Jaakko,

Thank you for the response.

So, I've include new cross-sections in the following fashion in my material deck:

Code: Select all

   72179.80c  4.59837192797259E-05
   72379.10c  0.0
which, I added like so in the xsdata file - I also had to edit the naming convention in the ACE:

Code: Select all

  72377.10c  72377.10c  1  72177  1  175.423200  293  0  /scratch/datafiles/Serpent/xsdata/tendl/Hf177m-n.ace
Then, in the .out it shows up a couple of times...:

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   89   0  72179.80c     80c  TRA   72 179 0  178.95028   294.0       stable  IBAD--T-I------R----  hafnium 179 (Hf-179)
   90   0  72379.10c     10c  TRA   72 179 1  177.40860   293.0  3.71263E-02  IB----T--------R----  hafnium 179m (Hf-179m)
  314   1  721790        10c  DEC   72 179 0  178.94574   293.0       stable  -BAD-----------R----  hafnium 179 (Hf-179)
  315   2  721792        10c  DEC   72 179 2  178.94574   293.0  3.20261E-07  -B-D-----------R----  hafnium 179m (Hf-179m)
  316   2  721792        80c  DEC   72 179 2  178.94574   294.0  3.20261E-07  -B-D-----------R----  hafnium 179m (Hf-179m)
  
Notable, the first isomeric state of 179m gets converted to the second metastable state? Noting that 179n (the second metastable) is really what we're trying to capture since it's half-life is ~25 days. I just find it a little strange that adding the cross-sections causes some issue.

But, in the depletion output there's no Hf179m:

Code: Select all

4.59837E-05 4.59871E-05 4.59922E-05 4.60180E-05 4.61547E-05 4.63290E-05 4.66771E-05 4.73849E-05 4.81077E-05 4.88407E-05 4.95947E-05 % Hf179
0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 % Hf179m
However, without having included the cross-section (vanilla Serpent data), it shows up in the .out it looks like:

Code: Select all

     87   0  72179.80c     80c  TRA   72 179 0  178.95028   294.0       stable  IBAD--T-I------R----  hafnium 179 (Hf-179)
314   1  721790        10c  DEC   72 179 0  178.94574   293.0       stable  -BAD-----------R----  hafnium 179 (Hf-179)
269   2  721792        80c  DEC   72 179 2  178.94574   294.0  3.20261E-07  -B-D-----------R----  hafnium 179m (Hf-179m)
And in the depletion output, the activity calculated - which should be equivalent to Hf181...:

Code: Select all

0.00000E+00 7.34738E-05 4.35684E-04 5.13253E-03 2.36896E-02 5.40949E-02 8.06392E-02 8.58060E-02 1.20636E-01 1.73453E-01 1.89165E-01 2.33855E-01 2.24755E-01 1.97938E-01 2.83241E-01 2.49209E-01 2.78823E-01 2.53719E-01 2.05171E-01 2.67640E-01 3.41435E-01 1.67330E-01 2.72564E-01 3.62109E-01 % Hf179m
0.00000E+00 7.32999E+08 1.83108E+09 7.32608E+09 3.53161E+10 6.79467E+10 1.25534E+11 1.30758E+11 1.74328E+11 2.15785E+11 2.51203E+11 2.81210E+11 3.28202E+11 3.61972E+11 4.02903E+11 4.16279E+11 4.33667E+11 4.48615E+11 4.50778E+11 4.52986E+11 4.54199E+11 4.55454E+11 4.58162E+11 4.60647E+11 % Hf181
Mass density:

Code: Select all

0.00000E+00 1.19936E-21 7.11192E-21 8.37814E-20 3.86699E-19 8.83023E-19 1.31632E-18 1.40066E-18 1.96921E-18 2.83138E-18 3.08785E-18 3.81736E-18 3.66880E-18 3.23106E-18 4.62351E-18 4.06799E-18 4.55139E-18 4.14160E-18 3.34913E-18 4.36884E-18 5.57344E-18 2.73143E-18 4.44923E-18 5.91092E-18 % Hf179m
0.00000E+00 2.04743E-08 5.11462E-08 2.04634E-07 9.86459E-07 1.89791E-06 3.50645E-06 3.65236E-06 4.86939E-06 6.02735E-06 7.01667E-06 7.85485E-06 9.16744E-06 1.01107E-05 1.12540E-05 1.16276E-05 1.21133E-05 1.25308E-05 1.25912E-05 1.26529E-05 1.26868E-05 1.27219E-05 1.27975E-05 1.28669E-05 % Hf181
I'll hunt around a little bit more in the meantime with the option you provided.

jesse.johns
Posts: 114
Joined: Wed Apr 20, 2011 5:19 am

Re: Hafnium Metastable

Post by jesse.johns » Tue Feb 21, 2017 5:48 pm

Also, to note, the branching ratio to Hf179m from Hf178 (n,g) is about 38% based on my chart of the nuclides. So, I changed it via:

Code: Select all

set isobra 721792 102 0.62
Is that correct?
ZAIn : isotope ZAI (10000 x Z + 10 x A + I)
MTn : ENDF reaction MT
FGn : fraction of reactions leading to the ground state of the product nuclide
I'm am confused a bit by what FGn is referring to - the product nuclide of the isobar decay or the product of the parent nuclide 72178? I would expect - (1 - branching ratio of Zr178 (n,g) Zr179m)? But the the actual language would suggest that I should put 1.0, since the decay of Hf179m goes to Hf179 ground state 100% of the time.

With the change above, I still get very little production. I also tried JEFF3.11.

I appreciate any clarification.

jesse.johns
Posts: 114
Joined: Wed Apr 20, 2011 5:19 am

Re: Hafnium Metastable

Post by jesse.johns » Fri Mar 24, 2017 5:11 pm

Well, I just wanted to vindicate Serpent on this - we just measured our samples and there was no Hf-179n. I did some additional calculations and I wasn't able to predict the Hf-179n that a few other (nominally trusted) codes predicted.

Cheers!

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