Sets of nuclides of interest are saved in files with the “.nucx” extension. They contain a set of “nuclide” elements (one for each nuclide in the set), enclosed by a single “nuclides” element:
<nuclides name=str> <nuclide>str</nuclide> ... </source>
The “nuclides” element has one attribute “name” containing the name of the set of nuclides. Each of “nuclide” elements contain the name of the nuclide as the value.
<nuclides name="Eu"> <nuclide>Eu-152</nuclide> <nuclide>Eu-154</nuclide> <nuclide>Eu-155</nuclide> <nuclide>Eu-156</nuclide> </source>