# Fatal Error in MCNP6

#### muthboravy

Hello everyone here,

I do need your help in this matter, please kindly help me solve this problem. I am new to this forum and now am seeking for help.

I am new to MCNP code, and I run MCNP6 code using BURN card and it give me fatal error say "Model required. Cannot use memory reduction option".

the whole input are below

C FUEL ASSEMBLY 17x17
C ==== fuel, Universe 1 =====================
1 1 -10.176 -1 u=1 vol=105.30977 imp:n=1
3 2 -6.56 1 -3 u=1 imp:n=1
4 3 -0.998207 3 u=1 imp:n=1
c ===== Guide Tube Uinverse 4================
6 3 -0.998207 -10 u=4 imp:n=1
7 2 -6.56 10 -11 u=4 imp:n=1
8 3 -0.998207 11 u=4 imp:n=1
c ===== Instructmentation Tube Universe 5====
10 3 -0.998207 -10 u=5 imp:n=1
11 2 -6.56 10 -11 u=5 imp:n=1
12 3 -0.998207 11 u=5 imp:n=1
c ========= SLOBA 15% Universe 3=============
13 5 -3.52 -50 u=3 vol=25.13274 imp:n=1
14 6 -0.001205 50 -51 u=3 vol=60.88407 imp:n=1
15 2 -6.56 51 -52 u=3 vol=4.712389 imp:n=1
16 5 -3.52 52 -53 u=3 vol=14.89115 imp:n=1
17 6 -0.001205 53 -54 u=3 vol=11.42193 imp:n=1
18 2 -6.56 54 -55 u=3 vol=25.31963 imp:n=1
19 3 -0.99827 55 u=3 vol=176.3183586 imp:n=1
c ===== Lattice Assembly ====================
100 3 -0.998207 -12 13 -14 15 4 -5 u=10 lat=1 imp:n=1 &
fill=-8:8 -8:8 0:0 &
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 & $1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 &$ 2
1 1 3 1 1 4 1 1 4 1 1 4 1 1 3 1 1 & $3 1 1 1 4 1 1 1 1 1 1 1 1 1 4 1 1 1 &$ 4
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 & $5 1 1 4 1 1 4 1 1 4 1 1 4 1 1 4 1 1 &$ 6
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 & $7 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 &$ 8
1 1 4 1 1 4 1 1 5 1 1 4 1 1 4 1 1 & $9 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 &$ 10
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 & $11 1 1 4 1 1 4 1 1 4 1 1 4 1 1 4 1 1 &$ 12
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 & $13 1 1 1 4 1 1 1 1 1 1 1 1 1 4 1 1 1 &$ 14
1 1 3 1 1 4 1 1 4 1 1 4 1 1 3 1 1 & $15 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 &$ 16
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 \$ 17
101 3 -0.998207 -16 17 -18 19 4 -5 fill=10 imp:n=1
102 2 -6.56 -20 21 -22 23 4 -5 #101 imp:n=1
103 0 20:-21:22:-23:-4:5 imp:n=0

c ========= Fuel Pin ==========
c /////surface card//////
c ======fuel pin======
1 cz 0.4095
2 cz 0.4175
3 cz 0.4750
c ===surface===
*4 pz -100
*5 pz 100
C =========guide tube=======
10 cz 0.57
11 cz 0.61
C ===========Lattice===================
12 px 0.627
13 px -0.627
14 py 0.627
15 py -0.627
C ====Assembly=====
16 px 10.659
17 px -10.659
18 py 10.659
19 py -10.659
c =====Surround of assembly===========
*20 px 10.75
*21 px -10.75
*22 py 10.75
*23 py -10.75
c ======SLOBA geometry================
50 cz 0.2000
51 cz 0.3700
52 cz 0.3800
53 cz 0.4100
54 cz 0.4316
55 cz 0.4760

C ======== Data Card ==========
kcode 1000 1.0000 50 200
ksrc 10.032 0 0 -10.032 0 0
0 10.032 0 0 -10.032 0
10.032 10.032 0 -10.032 -10.032 0
BURN TIME 0.1 0.2 0.3 0.4 1 2 10 15 25
POWER 1.0
MAT 1
MATVOL 86552.05632
BOPT 1 14 1
OMIT=1 8 90233 90234 91232 93235 93236 93239 94236 94237
C ======== Material Card ======
c UO2 d=10.17g/cc
m1 92235 -0.0436342
92238 -0.837866
8016 -0.1185
c --- cladding Zircaloy-4 d=6.560 g/cc ----------
m2 8016 -0.001196
24000 -0.000997
26000 -0.001994
40000 -0.981858
50000 -0.013955
c -------water d=1g/cc
m3 1001 -0.111894 8016 -0.888106
c -------He gas d=0.000166
c m4 2004 -1.0
c -------SLOBA 15% B4C-Al2O3 d=3.520 g/cc
m5 5010 -0.023470
5011 -0.093910
8016 -0.400130
24000 -0.449860
6000 -0.032600
c -------Air d=0.001205g/cc
m6 6000 -0.000124
7014 -0.755268
8016 -0.231781
18000 -0.012827
==================================================

please kindly help, and i couldn't find the problem at all.

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#### PF_Help_Bot

Thanks for the thread! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post? The more details the better.

#### OmnipotentEntity

I also ran into this problem. My source file is a bit more complex, but it boiled down to the following problem:

1. Physics models were disabled. Why? Dunno. It seems like literally every source file I write I get this message.
2. An isotope without tables was encountered.
3. In order to estimate the behavior of this isotope under radiation it needs to have physics models enabled or a lookup table in the burn up.

In your out file there should be a line telling you what zaid of the isotope(s) it's choking on, for me this happened to be 64151 (which is a stable isotope of Gadolinium apparently, I never specified it in my input file, but I guess as part of the burnup calculation it was generated.)

Here's my omit block:

OMIT=-1 114,6014,7016,8018,9018,10021,10022,12023,
12027,13026,13028,14027,14031,16031,16037,
17034,17036,17038,18037,18039,18041,18042,
19042,19038,19043,20039,20041,20045,20047,
21044,21046,21047,21048,2045,22051,223047,
23048,23049,23050,23052,23053,23054,24049,
24051,24052,24055,24056,25051,25052,25053,
25054,25056,25057,25058,26053,26055,26059,
26060,27057,27060,27061,27062,27063,28057,
28063,28065,29062,29064,29066,30064,30065,
30066,30067,30068,39087,39092,39093,40088,
40089,40097,41091,41092,41093,41096,41097,
41098,41099,41100,42093,42091,42101,43097,
43098,44097,54127,56131,58137,64151,90231,
90234,90233,91230,91232,93235,93236,94243,
94244,94236,94237,95240,95244,97245,97246,
97247,97248

#### dboozer

I haven't tried to run your code, but one thing that may be helpful is to specify which cross section libraries you want to use. You'll need to consult the manual to see which ones match your problem best, but you'll probably be fine in using .80c.

So for each ZAID, try this: for Hydrogen, instead of using 1001, use 1001.80c. For O-16, use 8016.80c. Etc etc.

#### DEvens

Gold Member
OK, this is a very old thread. But I just learned the answer. You need to use the MPHYS card to turn on model physics.

MPHYS ON

By default it's off. The error message is pretty weird.

"Fatal Error in MCNP6"

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