Problem with moderator temperature branch to cold conditions

User feedback and discussion on methods for group constant generation in Serpent 2
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topefo
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Problem with moderator temperature branch to cold conditions

Post by topefo » Sun May 26, 2019 9:46 pm

Hi all!

When I try to use the branch functionality in Serpent2 to cold conditions, i.e. Tm = 294 K,
I get an error message. Only when I change this temperature to 300 K or above, this case
goes through successfully with the input below:

% --- Moderator water (313 K):

mat water -0.99222 tmp 313.0 moder lwtr 1001 rgb 0 0 255
1001.03c 0.66667
8016.03c 0.33333

branch brch_CT_300
xenon 1 % Xenon from restart file
samarium 1 % Samarium from restart file
stp water -0.99222 300 lwtr lwe7.00t lwe7.02t
stp boron 1.00000 300

Am I missing something here, can one NOT specify the lowest temperature of the temperature
interval of scattering data below?

lwe7.00t lwe7.00t 3 0 0 1.007825 294 0 ./acedata/sssth1
lwe7.02t lwe7.02t 3 0 0 1.007825 350 0 ./acedata/sssth1

I also tried also 295 K without success.

Cordially,
Petri

topefo
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Re: Problem with moderator temperature branch to cold conditions

Post by topefo » Sun May 26, 2019 9:57 pm

After some thoughts I just wonder, although the error message refers to the water material, the boron could be the problem here
as the lowest temperature of boron is 300 K.

topefo
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Re: Problem with moderator temperature branch to cold conditions

Post by topefo » Sun May 26, 2019 10:28 pm

Unfortunately, removing the boron from the branch definition did not resolve the problem.

Ville Valtavirta
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Re: Problem with moderator temperature branch to cold conditions

Post by Ville Valtavirta » Mon May 27, 2019 9:11 am

Hi Petri,

I think this problem might be related to the fact that the basic cross sections are at 300 K (the .03c) and Serpent will not (cannot) adjust those below 300 K. You could use zero kelvin cross section data (.00c) if your cross section library includes it. Otherwise it is a bit difficult to go from 300 K to 294 K.

-Ville

topefo
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Re: Problem with moderator temperature branch to cold conditions

Post by topefo » Mon May 27, 2019 8:45 pm

Thanks Ville for your fast response!

Ok, so the basic XS data has preference over the bound scattering data. Good to know, thanks!

Cordially,
Petri

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