Neutron flux spatial distribution

User Support
1

Hello,

I’m trying to determine the neutron flux distribution over an integral small pressurized water reactor (PWR ) core by OpenMC. To investigate that, I created a 2D mesh flux tally cover whole core on XY domain. I got the data from the simulations, but the results look very strange.

I attach the core geometry of this simulation and the calculated neutron flux mesh plot in this letter. Usually, the neutron flux in PWR is high in the centre area and low in the edge area, but this simulation result presents oppositely.

If anyone knows the reason why this situation happened, please let me know. The XML files of material, simulation settings and Tallies were attached in as well, Welcome to check it.

Many Thanks for your help!!

11th_June_no_Gd_thermal_NU_flux_9sources .png

core1.png
core1.png3000×3000 75.8 KB

settings.xml (1.49 KB)

tallies.xml (569 Bytes)

materials.xml (1.3 KB)

2

Hello Yiming,

Double check the values in the materials.xml file. The water nuclides are in a ratio of 2 O per 1 H rather than 2 H per one O. For the fuel, you perhaps want to use “wo” (weight occurrence) rather than “ao” (atomic occurrence). The results are also likely not converged in terms of inactive batches and neutrons per batch. The exact numbers depend a lot on your specific model and what your objectives are, but running a full-core simulation like this will probably require >1 million particles per batch and >100 inactive batches.