Fission Yield Data Manipulation

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Fission Yield Data Manipulation

Postby TeaEye5400 » Tue Feb 27, 2018 2:48 pm

Hello!

I am a learning to use Serpent as a part of my university course. For the purposes of an investigation, I want to learn a bit more about how Serpent reads and interprets the fission yield data it is given. More specifically, how is the energy dependence of yields accounted for in the condensation of the energy groups?

Thanks in advance!
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Re: Fission Yield Data Manipulation

Postby Jaakko Leppänen » Thu Mar 01, 2018 2:08 pm

Do you mean fission neutron yields or fission product yields?

Neutron production cross sections ("nu-sigma_fission") are condensed into multi-group constants similar to reaction cross sections.

Fission product yields are provided at two or three energies (thermal, fast, high-energy), and Serpent essentially performs linear interpolation between the data. Fission product yields are not condensed into multiple energy groups (apart from fission product poisons, if requested by the "set poi" card).
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Re: Fission Yield Data Manipulation

Postby TeaEye5400 » Thu May 17, 2018 12:39 pm

Hi Jaakko,

Thanks for the reply!

It is still not clear how the fission rate weighted average fission yield value is calculated to be then used in burnup matrix.
One would need a multi-group flux and fission cross section to collapse the (linearly) energy dependent fission yield into one group.
Is this a correct interpretation of the Serpent approach?

Can you please point me to the subroutine in Serpent source where this operation is performed?

Thanks again!
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Re: Fission Yield Data Manipulation

Postby Jaakko Leppänen » Thu May 17, 2018 2:24 pm

It gets pretty complicated. Basically Serpent creates duplicates corresponding to each yield, and calculates their transmutation cross sections separately. The reaction rates are scored in scoretransmuxs.c, line 225 onwards.
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