Section I

I. Files and Procedures

A. Input files for initiate-run and continue runs (1-21,1-28,3-1)

Initiate-Run

 MESSAGE block followed by blank line delimiter     (optional)                  (1-21)
    title card     (required - one line of 80 characters or less)
    cell cards
 blank line delimiter
    surface cards
 blank line delimiter
    data cards
 blank line terminator (recommended but not required unless other data follows)
    anything else may be put after blank line terminator, but will not be used

Continue (requires a RUNTPE file) (3-2)

 CONTINUE 
 data cards allowed in a continue run 
      (CTME,DBCN,DD,FQ,IDUM,KCODE,LOST,MPLOT,NPS,PRDMP,PRINT,RDUM,ZA,ZB, and ZC)
 blank line terminator (recommended)
    anything else may be put after blank line terminator, but will not be used

B. MCNP execution line (1-29)

mcnp options files
examples:

MCNP execution line options and useful combinations{IXR} (1-30)

 I       set up the problem specified in the INP file and check for input errors
 X       get the cross section tables required by the problem
 R       run the problem
 P       plot the problem geometry from INP or RUNTPE files
 Z       plot the problem results from RUNTPE or MCTAL files
 
 IXR     set up the problem, get cross sections, and run the problem {default}
 IP      set up the problem and plot the geometry from an INP file
 IX      set up problem and check for INP and material cross section errors
 IPXRZ   do everything possible

 C m     perform a continue run starting with dump m (omitting m uses last dump)
 CN      continue run but write each dump immediately after fixed data on RUNTPE
 D       destroy a drop file if one is created and MCNP terminates normally
 DBUG n  write DBCN debug information every n histories
 FATAL   run the problem even if fatal input errors are found
 NOTEK   terminal has no graphics capabilities - plot output to local film files
 PRINT   create the full full output file (same as a blank PRINT card)
 TASKS m use m CPUs to run this problem (requires multitasked MCNP version)

C. Input and output file names (1-29,B-3)

 COM=     plot input command file
 COMOUT=  output plot command file
        
 DUMN1=   dummy file name
 DUMN2=   dummy file
        
 INP=     problem specifications (not in the MESSAGE block)
 MCTAL=   tally output file
        
 OUTP=    output for printing
 PLOTM=   graphics metafile
 PTRAC=   particle tracks file
        
 RSSA=    binary surface source read file
 RUNTPE=  binary problem start-restart data
        
 SAMFIL   binary memory access pattern analysis
 SRCTP=   binary kcode source distribution
        
 WSSA=    binary surface source write file
 WXXA     binary surface source scratch file
        
 XSDIR=   cross-section tables directory
        
 name or n=file  creates file names with letters appended to end of file:
          fileo=OUTP
          filem=MCTAL
          filer=RUNTPE
          files=SRCTP

D. Units for MCNP quantities (1-19)

 length in centimeters
 energies in MeV
 time in shakes (1e-8 seconds)
 temperatures in MeV (kT)
 densities: atomic in atoms/bn-cm, mass in gm/cc
 cross sections in barns (1e-24 cm^2)

E. MCNP interrupts (1-31)

 (ctrl c)         MCNP problem status
 (ctrl c)s            MCNP problem status
 (ctrl c)m            make interactive tally plots
 (ctrl c)q            terminate MCNP normally after current history
 (ctrl c)k            kill MCNP immediately

F. Procedures and commands to run specific types of problems (5-1,5-64)

1. Fixed source problem (1-21,5-1,5-10,5-50)

define types of particles to be run in problem using the MODE command (1-24,3-19)
specify SDEF source (or user sub SOURCE(4-50) (SRCDX(4-51) for pt detectors)) (3-39)
use tips for correct and efficient problems (1-31)
inspect tally fluctuation chart bin for ten statistical check results (2-106)

form statistical confidence intervals for precision of the result (2-105)

example INP file for a point cf-252 fixed source in a water cylinder:

 point cf-252 fission source in a cylinder of water
 c     begin cell cards for fixed source sample problem
 1 1 -1.  -1 -2 3             $ cylinder of water
 2 0       1:2:-3             $ all space outside the cylinder
 c       end cell cards for fixed source sample problem

 c    begin surface specifications 
 1 cy  20.                    $ cylinder about the y axis
 2 py  10.                    $    top plane of water cylinder
 3 py -10.                    $ bottom plane of water cylinder
 c      end surface specifications

 c    begin data section
 mode n p                      $ this is a coupled neutron-photon problem
 sdef erg=d1 pos=0 0 0 cel=1   $ define a cf-252 pt source at the origin
 sp1 -3 1.025 2.926            $ use a watt fission spectrum for cf-252
 imp:n,p  1 0
 m1  1001 .66667  8016 .33333  $ define h2o using h and o atom fractions 
 mt1 lwtr                      $ use h2o S(a,b) thermal neutron treatment
 f1:n  1 2 3 (1 2 3)   $ neutron current tally over all sufaces and total
 f11:p 1 2 3 (1 2 3)   $  photon current tally over all sufaces and total
 f4:n  1               $ tally the average neutron flux in water cylinder
 f14:p 1               $ tally the average  photon flux in water cylinder
 nps  40000            $ run 40000 neutron histories in this calculation
 print                 $ print everything about the calculation
 c      end data section

2. Keff criticality eigenvalue problem (2-141,5-64)

use the seven entries on the KCODE command to define # of keff cycles, etc. (3-57)
requires KSRC or SDEF card or SRCTP file for the initial spatial fission source(3-58)
use enough settle cycles to reach fundamental spatial mode(see printed plots) (2-149)
use tips for correct and efficient problems (1-31)
a CONTINUE run requires only the RUNTPE file (3-2)
inspect cell sampling, keff data normality, batched data, and printed plots (2-149)

form statistical confidence intervals for precision of the keff result (2-148)

example keff INP file for GODIVA:

 godiva: skip 10 and run a total of 110 keff cycles with 1000 neutrons per cycle
 1    1  -18.74  -1  imp:n=1   $ enriched uranium sphere (godiva)
 2    0           1  imp:n=0   $ all space outside the sphere

 1    so 8.741                 $ radius of the godiva sphere

 kcode 1000 1.0 10 110         $ kcode defines a criticality calculation
 ksrc  0 0 0                   $ initial keff spatial dist is point at origin
 m1    92235 -93.71  92238 -5.27  92234 -1.02  $ define u with weight fractions

Todd Postma (tapostma@nuc.berkeley.edu)