<?xml version='1.0' encoding='utf-8'?>
<model>
  <materials>
    <material depletable="true" id="1" name="UO2">
      <density units="g/cm3" value="10.0"/>
      <nuclide ao="1.0" name="U235"/>
      <nuclide ao="2.0" name="O16"/>
    </material>
    <material id="2" name="light water">
      <density units="g/cm3" value="1.0"/>
      <nuclide ao="2.0" name="H1"/>
      <nuclide ao="1.0" name="O16"/>
      <sab name="c_H_in_H2O"/>
    </material>
  </materials>
  <geometry>
    <cell id="1" material="1" region="-1" universe="1"/>
    <cell id="2" material="2" region="1" universe="1"/>
    <cell id="3" material="1" region="-2" universe="2"/>
    <cell id="4" material="2" region="2" universe="2"/>
    <cell fill="3" id="5" universe="4"/>
    <cell fill="5" id="6" region="3 -4 5 -6" universe="6"/>
    <lattice id="3">
      <pitch>1.2 1.2</pitch>
      <outer>1</outer>
      <dimension>2 2</dimension>
      <lower_left>-1.2 -1.2</lower_left>
      <universes>
2 1 
1 1 </universes>
    </lattice>
    <lattice id="5">
      <pitch>2.4 2.4</pitch>
      <dimension>2 2</dimension>
      <lower_left>-2.4 -2.4</lower_left>
      <universes>
4 4 
4 4 </universes>
    </lattice>
    <surface coeffs="0.0 0.0 0.4" id="1" type="z-cylinder"/>
    <surface coeffs="0.0 0.0 0.5" id="2" type="z-cylinder"/>
    <surface boundary="reflective" coeffs="-2.4" id="3" name="minimum x" type="x-plane"/>
    <surface boundary="reflective" coeffs="2.4" id="4" name="maximum x" type="x-plane"/>
    <surface boundary="reflective" coeffs="-2.4" id="5" name="minimum y" type="y-plane"/>
    <surface boundary="reflective" coeffs="2.4" id="6" name="maximum y" type="y-plane"/>
  </geometry>
  <settings>
    <run_mode>eigenvalue</run_mode>
    <particles>1000</particles>
    <batches>10</batches>
    <inactive>5</inactive>
  </settings>
  </model>
