Dear community,

I want to define a geometry in MCNP with several levels of universes and fills, say:

c cells

10 100 -1 -1 u=1

11 0 1 u=1

c

30 0 -2 fill=1 u=2

31 0 2 u=2

c

40 0 -3 fill=2

41 0 3

Universe 1 consists of cells 10 and 11 and fills cell 30. Cells 30 and 31 make up universe 2 and fill cell 40. (I have not tested the above piece of code for errors but I hope you got the idea.)

Now I want to define an identical geometry where the material in cell 10 is changed from 100 to 200. Is there a way to do this?

"20 like 10 but mat=200 u=3" is possible, of course. However, then the entire remaining code must be copied (with adapted cell and universe numbers) in order to make up new universes. Is there something like "50 like 40 but ***mat of cell 10 within cell 30 within cell 40***=200"?

An alternative solution could be to define the material of 10 as a distribution depending on which higher-level cell cell 10 will be in (like mat=Fcel D1; SI1 L 50 40; SP1 100 200). But I do not see a way to access the cell numbers of higher level either.