Rotational Symmetry in MCNPX core design

[Perwaz Hussain]

Designing a PWR core in MCNPX for burnup using 4 folds rotational symmetry to reduce computational time of the core, taking reflective boundary conditions on rotational symmetry planes. should the power be reduced to 1/4th of original power (3000 MWth) in burnup card or does the reflective boundary condition demands to give power as for the whole core i.e. 3000 MWth?

 

[rpp]

Short answer - reduce the power by 1/4th. MCNPX doesn't know enough about your geometry to know that you are only modeling 1/4 of the core.
(for example, you could be running 1/8th of a core with reflective boundary conditions).

There are codes that are specifically designed for modeling LWR cores. For these codes, you usually input the full-core power and the code
automatically adjusts the power depending on the symmetry. Read the code documentation for confirmation.