User feedback and discussion on methods for group constant generation in Serpent 2
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Jaakko Leppänen
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Post by Jaakko Leppänen » Sun Jun 15, 2014 3:09 pm

I received several comments that calculating the ADF's is something that should be done within the nodal code, to ensure that the homogeneous diffusion flux is calculated using the exact same methods that are used for the global flux solution. I agree that this is clearly the best option, but I also beleive that all codes are not capable of doing this on their own (including the codes we use at VTT). For this reason we decided to add the internal diffusion flux solver, which, of course, doesn't mean that the ADF produced by Serpent have to be used in the calculation. The output also includes:

- Inward, outward and net currents integrated over faces, face mid-points and corners
- Heterogeneous flux integrated over the same regions
- Heterogeneous flux integrated over volume
- Dimensions of the homogenized region and the segments used for calculating corner fluxes

The ADF card itself has an option (since update 2.1.21) to apply symmetries for the geometry, which gets rid of the random noise in the values. This is important in Monte Carlo based group constant generation, since small imbalance in the local symmetry is amplified in the core-level calculation if similar assemblies are loaded in the core in the same orientation.

We will also provide different options on how to apply the boundary conditions in the internal diffusion flux solver. Currently the methodology works for 2D surface types (plane, infinite square and hexagonal prism), and we will start working on 3D surfaces once the current methodology is completed.

Let me know if there is anything missing in the ADF / surface current output.
- Jaakko

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