Add mass into Volume Calculation

[cfichtlscherer]

Description

Determine the weight of the cell in the volume calculation.

Implementation

In vol_calc.atoms, the total number of atoms present in each cell is already provided. To approximate the total weight, we can utilize the number of nucleons, which is indicated in the nuclide names. The overall weight can be calculated by first determining the molar quantity of each nuclide, then multiplying this by the respective number of nucleons for each nuclide, and finally summing these values. This method provides an effective way to estimate the total atomic weight within the cells.

Compatibility

I think there will be no compatibility issue.

My feeling would be that this could be helpful feature for many users, but I am happy for all thoughts on that.