<?xml version='1.0' encoding='utf-8'?>
<model>
  <materials>
    <material depletable="true" id="1" name="fuel">
      <density units="g/cc" value="11"/>
      <nuclide ao="1.0" name="U235"/>
    </material>
    <material id="2" name="cladding">
      <density units="g/cc" value="6.44"/>
      <nuclide ao="1.0" name="Zr90"/>
    </material>
    <material id="3" name="water">
      <density units="g/cc" value="1.0"/>
      <nuclide ao="2.0" name="H1"/>
      <nuclide ao="1.0" name="O16"/>
    </material>
  </materials>
  <geometry>
    <cell id="1" material="1" region="-1" universe="1"/>
    <cell id="2" material="2" region="1 -2" universe="1"/>
    <cell id="3" material="3" region="2" universe="1"/>
    <cell fill="1" id="4" universe="2"/>
    <cell fill="3" id="5" region="3 -4 5 -6" universe="4"/>
    <lattice id="3">
      <pitch>4.0 4.0</pitch>
      <dimension>2 2</dimension>
      <lower_left>-4.0 -4.0</lower_left>
      <universes>
2 2 
2 2 </universes>
    </lattice>
    <surface coeffs="0.0 0.0 1.5" id="1" type="z-cylinder"/>
    <surface coeffs="0.0 0.0 1.7" id="2" type="z-cylinder"/>
    <surface boundary="reflective" coeffs="-4.0" id="3" name="minimum x" type="x-plane"/>
    <surface boundary="reflective" coeffs="4.0" id="4" name="maximum x" type="x-plane"/>
    <surface boundary="reflective" coeffs="-4.0" id="5" name="minimum y" type="y-plane"/>
    <surface boundary="reflective" coeffs="4.0" id="6" name="maximum y" type="y-plane"/>
  </geometry>
  <settings>
    <run_mode>eigenvalue</run_mode>
    <particles>100</particles>
    <batches>10</batches>
    <inactive>1</inactive>
  </settings>
  </model>
