niess / gdnp

Convert a GDML geometry to an MCNP card

GDNP

(GDML to MCNP converter)

Warning : this is a work in progress. See the Contributing section.

Description

The gdnp.py Python script converts a GDML geometry description to an MCNP card. Usage is as following:

./gdnp.py FILE.GDML

This will dump the result to stdout. Optionally, an output file can also be provided as 2^nd argument:

./gdnp.py FILE.GDML MCNP.CARD

An example of converted geometry is available in the examples folder. The corresponding input GDML is also provided.

Note that the script is implemented in bare Python 2.7, i.e. without dependencies. However, note also that it was only tested on Linux so far.

Contributing

Currently, the converter only supports a limited number of GDML geometries: tube (closed, centered), ellipsoid and intersection. Rotations are not implemented as well. In addition, the materials data needs to be manually filled in at the end of the card. Note that the materials index are properly mapped, though.

Additional geometries can be added by defining a convert_gdml_{{volume}} function, where {{volume}} must be substituted by the GDML name of the volume to convert. This function must return the MCNP bounding surfaces of the volume as a list of tuples. See for example the convert_gdml_tube function. The snippet below illustrates the syntax by converting a GDML centered Orb:

def convert_gdml_orb(volume, placement):
    """Convert a centered GDML orb to MCNP surfaces
    """
    r = volume["r"]
    if (placement[0] != 0) or (placement[1] != 0) or (placement[2] != 0):
        raise NotImplemented("offset orb")
    else:
        return [(-1, "SO", r)]

Each line of the returned list corresponds to a bounding surface. Note that the first item of the surface definition must indicate the surface sign for being inside the volume, see e.g. pages 3 and 4 of the MCNP primer.

License

The gdnp.py utility is under the MIT license. See the provided LICENSE file.