<?xml version="1.0"?>
<materials>

  <material id="1">
    <density value="10" units="g/cc" />
    <nuclide name="U235" ao="1.0" />
  </material>

  <material id="2">
    <density value="0.1" units="g/cc" />
    <nuclide name="H1" ao="0.1" />
  </material>

</materials>
