HTR-Pebble Simulation

User Support
1

Hi,
I have installed OpenMC and tried to model HTR pebble using Lattice sturcture but it is having 2D latice capability.
Is there any way to model 3D lattice using OpenMC.

Thnak You

2

Hi- you can actually use 3D lattices by specifying three entries on the ‘dimension’, ‘lower_left’, and ‘width’ sub-elements of the element in geometry.xml. My apologies that the user’s manual is not up-to-date in this respect. I will make appropriate changes to reflect the fact that 3D lattices are possible.

Please note that we still do not have hexagonal lattice capability.

Best regards,
Paul

3

Hi,

I was trying to make input for three dim lattice. Following massage I got while running with prepared input.

Input is given as under.

<?xml version="1.0"?>

< geometry>

rectangular 3 3 3 -0.25 -0.25 -0.25 0.125 0.125 0.125 None

Please help me.

Reading settings XML file…
Reading geometry XML file…
Error reading variable - tag = universes
ERROR: Number of universes on does not match size of lattice 5.
ERROR STOP

Backtrace for this error:

  • function __error_MOD_warning (0x43265C)
  • function __input_xml_MOD_read_geometry_xml (0x474C9A)
  • function __input_xml_MOD_read_input_xml (0x47D089)
  • function __initialize_MOD_initialize_run (0x4422E4)
  • in the main program
    from file main.F90
  • /lib64/libc.so.6(__libc_start_main+0xed) [0x3af4e2143d]
4

Hi Indrajeet,
None is not a valid option for the universes tag. The description at http://mit-crpg.github.io/openmc/usersguide/input.html#lattice-element is admittedly confusing when it says Default: None, but this is intended to imply that there is no default value and one must be specified.
So instead of the None option for universes, you should have a matrix of numbers, with each number corresponding to the universe number of the cells you have created. The dimensionality of this matrix is the same as the dimensionality of the lattice you are trying to fill (3x3x3 in this case). For example:

`

2 2 2
2 2 2
2 2 2

2 2 2
2 2 2
2 2 2

2 2 2
2 2 2
2 2 2

`

Having said that, I suspect your input has other issues related to the lack of a universe specified on cell 105 (which makes it default to universe 0, which may or may not be desired), and the fact that no universe (or universes) exist which can fit within one of the lattice elements (for this I would change the universe of cell 104 to 3 perhaps, and use three in the universes definition for lattice 5.

Paul and/or Bryan: Given that this does not seem to be an issue with the code itself, I suggest closing https://github.com/mit-crpg/openmc/issues/223 as wontfix, do you agree?

5

Hello Sir,

In this way, input will be very large for lattice of actual pebble geometry ( say 50x50x50 ). Is there any other procedure for 3D lattice input.

I tried your idea for 5x5x5 lattice and it was working properly. But how to model real problem.

Thank you

6

One way around that is to use ‘nested lattices’. That is, a lattice of lattices. An example can be found in the openmc/examples/lattice/nested/geometry.xml file which you may have, and if not here is the file from GitHub: https://github.com/mit-crpg/openmc/blob/develop/examples/lattice/nested/geometry.xml