# MCNP6 Fatal Error and warnings

#### khary23

Hello,
I am working through the MCNP6 manual and am experiencing the following error as well as warning when trying to run the sample problem from the manual.
The fatal error I get is
"fatal error. 1 entries not equal to number of cells = 4."
From the IMP card. My entry for that card is
IMP:N 1 1 1 0
which is exactly what they have in the manual.
After that I get the following error.

bad trouble in subroutine ixsdir of imcn

data file xsdir does not exist"
But I do see xsdir in the MCNP_DATA directory so I am a bit confused about that. I have upload the output file with the errors in case I have not properly explained whats going on.

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#### PSRB191921

hi
for your fatal error it is because you have twice "imp:n". one in line 22 and the other line 23. Remove line 22.
In MCNP6 "Xsdir" must be named "xsdir_mcnp6.1" so renamed the file "xsdir". But it is Strange I think that MCNP6 was not install correctly.

#### khary23

This is very strange. As you can see from the screen shot below IMP:N is only in line 24. I think I will uninstall and reinstall and see if that helps. Thanks for your help.

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#### PSRB191921

sorry,
too difficult to read. Can you copy/paste your file (or put a ascii file) ?

#### khary23

Here it is a a notepad file. Thank you for looking at it.

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#### khary23

I wanted to add that I looked and the file "xsdir_mcnp6.1" does exist in the MCNP_DATA folder.

#### PSRB191921

first you have 2 imp:n !
in block 1
Sample Problem Imput Deck
C cell cards for sample problem
1 1 -0.0014 -7 IMP:N=1
2 2 -0.786 -8
3 3 -1.060 1 -2 -3 4 -5 6 7 8
4 0 -1:2:3:-4:5:-6
C end of cell cards for sample problem

must have
1 1 -0.0014 -7 $IMP:N=1 second you have a cukie cutter : instead of C Surface Cards C Begining of surfaces for cube 1 PX -5$ 5cm negitive of x=0
2 PX 5 $5cm positive of x=0 3 PY 5 4 PY -5 5 PZ -5 6 PZ 6 C End of Cube surfaces C Begin Sphere Surfaces 7 S 0 -4 -2.5 0.5$ oxygen sphere
8 S 0 4 4 0.5 \$ iron sphere
C End sphères

you msut have :
5 PZ 5
6 PZ -6

and after it's ok (see file)

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#### khary23

I have no idea how the IMP:N=1 got into the cell card, thank you so much for pointing it out!

One last question why is
5 PZ -5
6 PZ 6
incorrect and

5 PZ 5
6 PZ -6
Correct?

#### PSRB191921

One last question why is
5 PZ -5
6 PZ 6
incorrect and

5 PZ 5
6 PZ -6
Correct?
because you write in block 1 :
3 3 -1.060 1 -2 -3 4 -5 6 7 8
so "-5" is on the left of geometry "5 PZ -5" but "PZ -5" is the left plan of your geometry
and 6 is on the right of geometry "6 PZ 6" but "PZ 5" is the right plan of your geometry

#### PSRB191921

is it ok with my modification ?

#### khary23

because you write in block 1 :
3 3 -1.060 1 -2 -3 4 -5 6 7 8
so "-5" is on the left of geometry "5 PZ -5" but "PZ -5" is the left plan of your geometry
and 6 is on the right of geometry "6 PZ 6" but "PZ 5" is the right plan of your geometry
That makes complete sense. Thank you

#### khary23

"MCNP6 Fatal Error and warnings"

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