last modified: 01-FEB-2002 | catalog | categories | new | search |

NESC0491 MOD5

MOD-5, Time-Dependent MultiGroup Slowing-Down Neutron Spectra and Keff Calculation, Green Function Method

top ]
1. NAME OR DESIGNATION OF PROGRAM:  MOD5
top ]
2. COMPUTERS
To submit a request, click below on the link of the version you wish to order. Only liaison officers are authorised to submit online requests. Rules for requesters are available here.
Program name Package id Status Status date
MOD-5 NESC0491/01 Arrived 01-FEB-2002

Machines used:

Package ID Orig. computer Test computer
NESC0491/01 IBM 360 series
top ]
3. DESCRIPTION OF PROBLEM OR FUNCTION

MOD5 calculates the time- and
energy-dependent evolution  of the neutron density  in homogeneous
media   following  initiation   of  a)   a  monoenergetic   source
distributed  over  a finite  time  interval,  or  b) a  source  of
arbitrary  spectrum with  a delta-function  distribution in  time.
Effectively the  code produces Green's  function solutions  to the
slowing-down  equation in  discrete  numerical  form.  Leakage  is
treated in the diffusion approximation.  The program a) calculates
spectra and energy  moments at selected times  following the burst
of  source  neutrons,  b)  evaluates  the  time-dependent  neutron
density and slowing-down density at selected energies and computes
moments   of  these   densities,   c)  calculates   time-dependent
distributions of capture,  leakage and first fission,  and moments
of these  distributions, d)  calculates steady-state  central core
neutron  flux and  leakage flux  in detail  and in  group-averaged
form, and e) calculates parameters such as keff.
top ]
4. METHOD OF SOLUTION

The  code  is  based  on  a  discrete  Markov
slowing-down model developed  by the author.  The  energy range of
interest in the  slowing-down region is divided  into an arbitrary
number of states and a Markov  matrix is constructed which defines
the probabilities for transition from one state to another in some
finite time  interval.  The neutron  density (defined as  a vector
over  the  state  structure)  is evolved  in  time  by  repetitive
multiplication of the  density vector into the  transition matrix.
Currently cross  sections are  derived from  the 26-group  Russian
set.  Capture,  fission, and leakage  events are accounted  for in
three absorbing states.
top ]
5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

Maxima of -
     5 isotopes
    71 real energy states
   201 virtual energy states
    26 broad groups for input cross sections
   400 time-steps
    21 time moments
    10 groups from which inelastic scattering can take place
The program has  been modified to handle up to  701 virtual energy
states and 201 real states.
top ]
6. TYPICAL RUNNING TIME

On  the  IBM360/67  the   running  time  in
seconds is given approximately  by the formula t = 0.004  n * nv +
10 where n  is the number of real  states and nv is  the number of
virtual states.
top ]
7. UNUSUAL FEATURES OF THE PROGRAM

(a) Elastic scattering transition probabilities are calculated         with a new stochastic algorithm, reference 1.
(b) The state structure can be calculated by the code to provide         optimal (most accurate) treatment of elastic scattering.
(c) Calculation times may be greatly reduced by allowing the         transition matrix to follow the neutron distribution.
This traveling array technique may also allow a much finer         state structure for a given core capacity.
(d) A unique transition matrix generating technique provides  transition matrices that are consistent, accurate, and         stable regardless of energy range or time-step width.
top ]
8. RELATED AND AUXILIARY PROGRAMS

SLOAD arranges the  cross section
library in  proper format and loads  it on the  appropriate direct
access device.
top ]
9. STATUS
Package ID Status date Status
NESC0491/01 01-FEB-2002 Masterfiled Arrived
top ]
10. REFERENCES

T.  J.  Williamson  and  R.  W.  Albrecht,  A  Direct
Stochastic  Model  for  Neutron Moderation,  Nuclear  Science  and
Engineering, Vol. 37, pp. 41-58, 1969.
             T. J. Williamson and R.  W. Albrecht, Calculations of
Neutron  Time-Energy Distributions  in  Heavy Moderators,  Nuclear
Science and Engineering, Vol. 42, pp. 89-111, 1970.
            L. P.  Abagyan, et  al., Group  Constants for  Nuclear
Reactor Calculations, Consultants Bureau, 1964.
             T. J. Williamson, MOD5 User's Manual, NPS-61WN71061A,
1971.
top ]
11. MACHINE REQUIREMENTS

175K  bytes memory,  normal input,  output,
program, and  punch units,  6 cylinders  of IBM2314  or equivalent
direct-access storage
top ]
12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
NESC0491/01 FORTRAN-IV
top ]
13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:   IBM360 CP-CMS.
top ]
14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:
top ]
15. NAME AND ESTABLISHMENT OF AUTHOR

                 T. J. Williamson
                 Physics Department, Code 61WN
                 Naval Postgraduate School
                 Monterey, California  93940
top ]
16. MATERIAL AVAILABLE
NESC0491/01
source program   mag tape                                           SRCTP
test-case data   mag tape                                           DATTP
test-case output mag tape                                           OUTTP
report                                                              REPPT
top ]
17. CATEGORIES
  • E. Space-Independent Kinetics

Keywords: multigroup, scattering, slowing-down, spectra, stochastic processes, time dependence.