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NESC0901 PAD.

PAD, Coupled Neutronics, Thermohydraulics in 1-D Spherical, Cylindrical, Planar Geometry

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1. NAME OR DESIGNATION OF PROGRAM:  PAD.
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2. COMPUTERS
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Program name Package id Status Status date
PAD NESC0901/01 Arrived 08-AUG-2001

Machines used:

Package ID Orig. computer Test computer
NESC0901/01 CDC 7600
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3. DESCRIPTION OF PROBLEM OR FUNCTION

The Pajarito Dynamics (PAD) program models dynamic systems with interactive neutronics, thermo-  dynamics, and hydrodynamics in one-dimensional spherical, cylin- drical, and planar geometries. The program has been applied to prompt critical excursions in various fissioning systems (solution,  metal, LMFBR, etc.) as well as to nonfissioning systems. PAD appli-  cations have included: controlled (nondestructive) and damaging reactor transient experiments, hypothetical LMFBR disassembly and recriticality accidents, hypothetical criticality accidents invol- ving the handling and processing of various forms of fissile mate- rials, and nonneutronic systems employing only the thermodynamic and hydrodynamic aspects of the program.
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4. METHOD OF SOLUTION

A system is divided into discrete, contiguous regions, or mass points. The neutronics is comprised of one- dimensional Sn transport calculations for determining the spatial power profile and material motion reactivity feedback and analytic models for input and temperature feedback reactivities. Equation-of- state models in the program describe the thermodynamics of solids, liquids, and vapors and also phase transitions. Heat transfer bet- ween two materials at a mass point is considered. The hydrodynamics  (acceleration, velocity, position) proceeds in a Lagrangian coordi-  nate system. The neutronic-thermodynamic-hydrodynamic cycle is repeated stepwise in space and time until the desired calculational  endpoint is reached.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

Maxima of -
   100 hydrodynamic regions
    40 materials
    16 neutron energy groups
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6. TYPICAL RUNNING TIME

A 16-group, S4, 20 mesh-point model of an LMFBR running for 10,000 iterations (time-steps) an including 50 Sn  calculations with a total of 20,000 inner iterations requires about  two minutes of CDC7600 time. The longest running sample problem requires approximately 95 CP seconds on the CDC7600.
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7. UNUSUAL FEATURES OF THE PROGRAM:
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8. RELATED AND AUXILIARY PROGRAMS

The internal geometric reactivity change is based on DTF4 (NESC Abstract 209). PAD disassembly calcu-  lations for a representative LMFBR model have been compared with those obtained from the FX2-POOL and VENUS2 (NESC Abstract 511) programs.
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9. STATUS
Package ID Status date Status
NESC0901/01 08-AUG-2001 Masterfiled Arrived
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10. REFERENCES

- T.P. McLaughlin, D.M. Peterson, and W.R. Stratton,
  Energy Release from Molten-Fuel Recriticality Accidents, Transac-
  tions of the American Nuclear Society, Vol. 18, pp. 198-199, June
  23-27, 1974.
- T.P. McLaughlin,
  Prelimanary Topical Report on Comparison Reactor Disassembly
  Calculations,
  LA-6106-MS, November 1975.
- T.P. McLaughlin,
  Effects of Neutron Streaming and Geometric Models on Molten Fuel
  Recriticality Accidents,
  LA-6127-MS, November 1975.
NESC0901/01, included references:
- D.M. Peterson, W.R. Stratton, and T.P. McLaughlin:
  PAD: A One-Dimendional, Coupled Neutronic-Thermodynamic
  Hydrodynamic Computer Code
  LA-6540-MS, (December 1976).
- PAD Tape Description and Implementation Information
  NESC Note 82-21 (October 1, 1981).
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11. MACHINE REQUIREMENTS

PAD requires system input and output units and a bulk storage device (e.g., disk or tape) on which four coded files may be defined. Each file should have a 32,000 (octal), 60-bit word capacity. PAD requires approximately 140K (octal) words of storage for execution on a CDC7600.
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12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
NESC0901/01 FORTRAN-IV
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13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:  SCOPE 2.1.5
(CDC7600).
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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

PAD was developed for the CDC RUN compiler with the rounded arithmetic option. Sample problem 2 terminates abnormally if rounded arithmetic is not used. Memory must be preset to zero prior to execution. Dummy routines are included in the package in place of several LANL com- puting environment routines. The dummy routines and their functions  are: XIT, an error interception routine; XITFIX, a routine to pro- vide the application program with the job status, program counter and program status words; GETHPK, a routine to provide the hardware  exchange package; DMPPK, which prints the exchange package; DMP, a routine to dump small core memory locations; and GETQ, which pro- vides various job parameters such as the job time limit, to the calling program.
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15. NAME AND ESTABLISHMENT OF AUTHOR

Authors      D.M. Peterson, W.R. Stratton, and
             T.P. McLaughlin

Contact      H.M. Forehand, Jr.
             Los Alamos National Laboratory
             P.O. Box 1663
             Los Alamos, New Mexico 87545
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16. MATERIAL AVAILABLE
NESC0901/01
source program   mag tapePAD Source Program (FTN)                   SRCTP
test-case data   mag tapeInput S. P. 1, Nonphysical Test Case       DATTP
test-case data   mag tapeInput S. P. 2, Nonneutronic Work Calcul.   DATTP
test-case data   mag tapeInput S. P. 3, Sodium Hammer Energetics    DATTP
test-case data   mag tapeInput S. P. 4, Sample Metal System-Cylin.  DATTP
test-case data   mag tapeInput S. P. 5, Sample Metal System Axial   DATTP
source program   mag tapeLISTIT Source Program (FTN)                SRCTP
test-case data   mag tapeGlossary of PAD COMMON Variable Names      DATTP
test-case data   mag tapePAD Input Specifications                   DATTP
source program   mag tapePAD CDC UPDATE Source Program              SRCTP
test-case output listing Sample Output                              OUTLS
test-case output listing Sample Problem Output (5 Microfiches)      OUTLS
report                   LA-6540-MS (1976)                          REPPT
prog. note               NESC Note 82-21 (October 1, 1981)          NOTPT
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17. CATEGORIES
  • F. Space - Time Kinetics, Coupled Neutronics - Hydrodynamics - Thermodynamics

Keywords: discrete ordinate method, excursions, feedback, hydrodynamics, one-dimensional, reactivity, temperature, thermodynamics.