<?xml version='1.0' encoding='utf-8'?>
<model>
  <materials>
    <material depletable="true" id="1">
      <density units="g/cm3" value="10.0"/>
      <nuclide ao="1.0" name="U235"/>
    </material>
    <material depletable="true" id="2">
      <density units="g/cm3" value="10.0"/>
      <nuclide ao="1.0" name="U238"/>
    </material>
    <material id="3">
      <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="3" region="1" universe="1"/>
    <cell id="3" material="2" region="-2" universe="2"/>
    <cell id="4" material="3" region="2" universe="2"/>
    <cell id="5" material="3" universe="30"/>
    <cell fill="4" id="6" region="-3" rotation="0.0 0.0 45.0" translation="-4.0 0.0 0.0" universe="5"/>
    <cell fill="3" id="7" region="-4" rotation="0.0 0.0 30.0" translation="4.0 0.0 0.0" universe="5"/>
    <cell id="8" material="3" region="-5 3 4" universe="5"/>
    <hex_lattice id="3" n_rings="3">
      <pitch>1.25</pitch>
      <outer>30</outer>
      <center>0.0 0.0</center>
      <universes>
  2
 1 1
1 2 1
 1 1
1 2 1
 1 1
1 1 1
 1 1
  1</universes>
    </hex_lattice>
    <lattice id="4">
      <pitch>1.25 1.25</pitch>
      <outer>30</outer>
      <dimension>4 4</dimension>
      <lower_left>-2.5 -2.5</lower_left>
      <universes>
2 2 2 2 
1 1 1 1 
1 1 1 1 
1 1 1 1 </universes>
    </lattice>
    <surface coeffs="0.0 0.0 0.25" id="1" type="z-cylinder"/>
    <surface coeffs="0.0 0.0 0.5" id="2" type="z-cylinder"/>
    <surface coeffs="-4.0 0.0 4.0" id="3" type="z-cylinder"/>
    <surface coeffs="4.0 0.0 4.0" id="4" type="z-cylinder"/>
    <surface boundary="vacuum" coeffs="0.0 0.0 8.0" id="5" type="z-cylinder"/>
  </geometry>
  <settings>
    <run_mode>eigenvalue</run_mode>
    <particles>1000</particles>
    <batches>5</batches>
    <inactive>0</inactive>
    <source particle="neutron" strength="1.0" type="independent">
      <space type="point">
        <parameters>0.0 0.0 0.0</parameters>
      </space>
    </source>
  </settings>
  </model>
