lc=5.0;

Point( 1)={ 0.0, 0.0,  0.0,lc};
Point( 2)={15.0, 0.0,  0.0,lc};
Point( 3)={20.0, 0.0,  0.0,lc};
Point( 4)={25.0, 0.0,  0.0,lc};

Point( 5)={15.0, 5.0,  0.0,lc};
Point( 6)={20.0, 5.0,  0.0,lc};
Point( 7)={ 0.0,15.0,  0.0,lc};
Point( 8)={15.0,15.0,  0.0,lc};
Point( 9)={ 0.0,25.0,  0.0,lc};
Point(10)={25.0,25.0,  0.0,lc};

Line(1)={1,2};
Line(2)={2,3};
Line(3)={3,4};
Line(4)={5,6};
Line(5)={7,8};
Line(6)={9,10};

Line(7)={1,7};
Line(8)={7,9};
Line(9)={2,5};
Line(10)={5,8};
Line(11)={3,6};
Line(12)={4,10};

Line Loop(13)={1,9,10,-5,-7};
Line Loop(14)={2,11,-4,-9};
Line Loop(15)={3,12,-6,-8,5,-10,4,-11};

Plane Surface(16)={13};
Plane Surface(17)={14};
Plane Surface(18)={15};

h1=15.0;

Extrude {0, 0, h1} { Surface{16}; }
Extrude {0, 0, h1} { Surface{17}; }
Extrude {0, 0, h1} { Surface{18}; }

h2=10.0;

Extrude {0, 0, h2} { Surface{ 45}; }
Extrude {0, 0, h2} { Surface{ 67}; } 
Extrude {0, 0, h2} { Surface{109}; }

Color Red{Volume{1};}
Color Blue{Volume{3,4,6};}
Color Yellow{Volume{2,5};}

Physical Point(100)={1,2,3,4,5,6,7,8,9,10};

// 11 for reflective, 12 for vacuum , 13 for zero flux boundary condition //

// 1 for core, 2 for reflector, 3 for control rod, 4 for empty //

Physical Surface(11)={16,17,18,44,92,135,183,28,54,80,119,145,171};
Physical Surface(13)={88,179,84,175,136,158,200};

Physical Volume(1)={1};//
Physical Volume(2)={3,4,6};
Physical Volume(4)={2,5};