Zaidtaher,
You have a problem with importance definition, I just specify the importance for each cell, that give me no fatal error. You still have to check, volumes and materials.
AP-1000 Core
c -----------------------CELL CARD---------------------------------------------
c
1 1 -10.97 -1 -8 9 u=2 imp:n=1 $FUEL Type 1
2 2 -0.004 1 -2 -8 9 u=2 imp:n=1 $GAP
3 3 -6.7 2 -3 -8 9 u=2 imp:n=1 $CLAD
4 4 -1 3 -4 5 -6 7 -8 9 u=2 imp:n=1 $MODIRATOR
5 0 4 :-5 :6 :-7 :8 :-9 u=2 imp:n=1
6 0 -10 11 -12 13 -8 9 fill=1 u=10 imp:n=1
7 0 10 :-11 :12 :-13 :8 :-9 imp:n=1
8 0 -4 5 -6 7 u=1 lat=1 $ROW 1
fill=-8:8 -8:8 0:0
2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 $ROW 1
2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 $ROW 2
2 2 2 2 2 0 2 2 0 2 2 0 2 2 2 2 2 $ROW 3
2 2 2 0 2 2 2 2 2 2 2 2 2 0 2 2 2 $ROW 4
2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 $ROW 5
2 2 0 2 2 0 2 2 0 2 2 0 2 2 0 2 2 $ROW 6
2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 $ROW 7
2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 $ROW 8
2 2 0 2 2 0 2 2 0 2 2 0 2 2 0 2 2 $ROW 9
2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 $ROW 10
2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 $ROW 11
2 2 0 2 2 0 2 2 0 2 2 0 2 2 0 2 2 $ROW 12
2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 $ROW 13
2 2 2 0 2 2 2 2 2 2 2 2 2 0 2 2 2 $ROW 14
2 2 2 2 2 0 2 2 0 2 2 0 2 2 2 2 2 $ROW 15
2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 $ROW 16
2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 $ROW 17
imp:n=1
9 7 -10.97 -1 -8 9 u=4 imp:n=1 $FUEL Type 2
10 2 -0.004 1 -2 -8 9 u=4 imp:n=1 $GAP
11 3 -6.7 2 -3 -8 9 u=4 imp:n=1 $CLAD
12 4 -1 3 -4 5 -6 7 -8 9 u=4 imp:n=1 $MODIRATOR
13 0 4 :-5 :6 :-7 :8 :-9 u=4 imp:n=1
14 0 -10 11 -12 13 -8 9 fill=3 u=11 imp:n=1
15 0 -4 5 -6 7 u=3 lat=1 $ROW 1
fill=-8:8 -8:8 0:0
4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 $ROW 1
4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 $ROW 2
4 4 4 4 4 0 4 4 0 4 4 0 4 4 4 4 4 $ROW 3
4 4 4 0 4 4 4 4 4 4 4 4 4 0 4 4 4 $ROW 4
4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 $ROW 5
4 4 0 4 4 0 4 4 0 4 4 0 4 4 0 4 4 $ROW 6
4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 $ROW 7
4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 $ROW 8
4 4 0 4 4 0 4 4 0 4 4 0 4 4 0 4 4 $ROW 9
4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 $ROW 10
4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 $ROW 11
4 4 0 4 4 0 4 4 0 4 4 0 4 4 0 4 4 $ROW 12
4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 $ROW 13
4 4 4 0 4 4 4 4 4 4 4 4 4 0 4 4 4 $ROW 14
4 4 4 4 4 0 4 4 0 4 4 0 4 4 4 4 4 $ROW 15
4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 $ROW 16
4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 $ROW 17
imp:n=1
16 8 -10.97 -1 -8 9 u=6 imp:n=1 $FUEL Type 3
17 2 -0.004 1 -2 -8 9 u=6 imp:n=1 $GAP
18 3 -6.7 2 -3 -8 9 u=6 imp:n=1 $CLAD
19 4 -1 3 -4 5 -6 7 -8 9 u=6 imp:n=1 $MODIRATOR
20 0 4 :-5 :6 :-7 :8 :-9 u=6 imp:n=1
21 0 -10 11 -12 13 -8 9 fill=5 u=12 imp:n=1
23 0 -4 5 -6 7 u=5 lat=1 $ROW 1
fill=-8:8 -8:8 0:0
6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 $ROW 1
6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 $ROW 2
6 6 6 6 6 0 6 6 0 6 6 0 6 6 6 6 6 $ROW 3
6 6 6 0 6 6 6 6 6 6 6 6 6 0 6 6 6 $ROW 4
6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 $ROW 5
6 6 0 6 6 0 6 6 0 6 6 0 6 6 0 6 6 $ROW 6
6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 $ROW 7
6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 $ROW 8
6 6 0 6 6 0 6 6 0 6 6 0 6 6 0 6 6 $ROW 9
6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 $ROW 10
6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 $ROW 11
6 6 0 6 6 0 6 6 0 6 6 0 6 6 0 6 6 $ROW 12
6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 $ROW 13
6 6 6 0 6 6 6 6 6 6 6 6 6 0 6 6 6 $ROW 14
6 6 6 6 6 0 6 6 0 6 6 0 6 6 6 6 6 $ROW 15
6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 $ROW 16
6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 $ROW 17
imp:n=1
24 6 -5 -1 -8 9 u=7 imp:n=1 $Control Material(black)
25 2 -0.004 1 -2 -8 9 u=7 imp:n=1 $Gap
26 3 -6.7 2 -18 -8 9 u=7 imp:n=1 $Clad
27 4 -1 18 -4 5 -6 7 -8 9 u=7 imp:n=1 $MODIRATOR
28 0 -10 11 -12 13 -8 9 u=9 lat=1 $ROW 1
fill=-4:4 -4:4 0:0
10 11 10 11 10 11 10 12 0 $ROW 1
0 10 11 10 11 10 12 12 0 $ROW 2
0 0 10 11 10 11 12 0 0 $ROW 3
0 0 0 10 11 12 12 0 0 $ROW 4
0 0 0 0 12 12 0 0 0 $ROW 5
0 0 0 0 0 0 0 0 0 $ROW 6
0 0 0 0 0 0 0 0 0 $ROW 7
0 0 0 0 0 0 0 0 0 $ROW 8
0 0 0 0 0 0 0 0 0 $ROW 9
imp:n=1
29 0 -19 20 -21 22 -8 9 fill=9 imp:n=1
30 0 19 :-20 :21 :-22 :8 :-9 imp:n=0
1 cz 0.4095
2 cz 0.41775
3 cz 0.47475
4 px 0.63
5 px -0.63
6 py 0.63
7 py -0.63
8 pz 215
9 pz -215
10 px 10.71
11 px -10.71
12 py 10.71
13 py -10.71
18 cz 0.43625
19 px 96.39
20 px -96.39
21 py 96.39
22 py -96.39
mode n
kcode 500 1.000000 50 1500
ksrc 0.000000 0.000000 0.000000
m1 92238. 0.855 $ type 1
92235. 0.045 8016. 0.1
m2 8016. 1 $ He2
m3 40090.70c 0.038189 $ Zirlo
40091.70c 0.008328 40092.70c 0.01273 40094.70c 0.0129
40096.70c 0.002078 50112.70c 7e-006 50114.70c 5e-006
50115.70c 3e-006 50116.70c 0.00011 50117.70c 5.8e-005
50118.70c 0.000183 50119.70c 6.5e-005 50120.70c 0.000247
50122.70c 3.5e-005 50124.70c 4.4e-005 41093.70c 0.000757
40090.71c 0.475264 40091.71c 0.101628 40092.71c 0.15534
40094.71c 0.157424 40096.71c 0.025362 50112.71c 9e-005
50114.71c 6.1e-005 50115.71c 3.1e-005 50116.71c 0.001344
50117.71c 0.00071 50118.71c 0.002239 50119.71c 0.000794
50120.71c 0.003011 50122.71c 0.000428 50124.71c 0.000535
41093.71c 0.009243
m4 8016. 0.66 $H2O
1001. 0.66
m5 6000.60c -0.0003 $ Structure Material
14000.60c -0.005 15031.60c -0.000225 16000.60c -0.00015
24050.60c -0.00793 24052.60c -0.159031 24053.60c -0.018378
24054.60c -0.004661 25055.60c -0.01 26054.60c -0.039996
26056.60c -0.644764 26057.60c -0.015026 26058.60c -0.002039
28058.60c -0.06234 28060.60c -0.024654 28061.60c -0.001085
28062.60c -0.003504 28064.60c -0.000917
m6 5010. 0.8 $ Control Material
6000. 0.2
m7 92235.66c 0.11 $ type 2
92238.66c 0.22 8016.62c 0.67
m8 92235.66c 0.07755 $ type 3
92238.66c 0.25245 8016.62c 0.67
f5:n 0 0 0 0.1