I have 3 points to ask about:
first, can open MC define more than 1 types of fuels in pebble bed reactors, may be 2 or 3 types of pebbles, with random packing for the pebbles?
second, if the core region is divided to different subregions, each subregion has the same volume but with different shapes, but contains the same type of pebbles for each subregion, does this problem applicable in open MC?
third, if we want to pack pebbles but with regular lattice, like BCC of FCC, how can we do this taking into consideration that it is 3D and number of pebbles may exceed 300000 pebble?