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NESC0380 GATT

GATT, 3-D Few-Group Neutron Diffusion for Power Distribution in Hexagonal Reactor Core for HTGR

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1. NAME OR DESIGNATION OF PROGRAM:  GATT
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2. COMPUTERS
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Program name Package id Status Status date
GATT NESC0380/01 Tested 01-NOV-1975

Machines used:

Package ID Orig. computer Test computer
NESC0380/01 IBM 370 series IBM 370 series
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3. DESCRIPTION OF PROBLEM OR FUNCTION

GATT  is a  three-dimensional
few-group  neutron diffusion  theory program  for calculating  the
detailed spatial  flux and  power distribution  for reactors  with
hexagonal  core   configuration.   The  program  uses   a  uniform
triangular  mesh  in the  horizontal  mesh  planes and  assumes  a
relatively simple region structure in the axial direction.  It was
designed to represent the special patch-type core structure of the
HTGR reactor as closely as possible.
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4. METHOD OF SOLUTION

GATT makes use of  the direct block inversion
technique for multidimensional reactor calculations (see reference
3).  This  method leads  to an improved  convergence of  the inner
spatial flux  iteration.  The  outer fission  source iteration  is
accelerated by an asymptotic source extrapolation which is applied
periodically to damp out the next higher eigenmode.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

GATT        allows
downscattering from one group into the next and a maxima of -
        81 z-planes
   104,487 mesh points
         4 energy groups
        40 macroscopic cross section sets (mixtures)
It is assumed that all fission neutrons are born in group 1.
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6. TYPICAL RUNNING TIME

A  four-group  problem   with  42,000  mesh
points, representing a 330 MW(e) HTGR reactor, with four fully and
three partially-inserted control rods requires 80 minutes.
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7. UNUSUAL FEATURES OF THE PROGRAM:
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8. RELATED AND AUXILIARY PROGRAMS

GAUGE (NESC Abstract  339) is the
two-dimensional counterpart of GATT.
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9. STATUS
Package ID Status date Status
NESC0380/01 01-NOV-1975 Tested at NEADB
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10. REFERENCES

H. Kraetsch  and   M.  R.  Wagner,  GATT,   A  Three-
dimensional  Few-group  Neutron  Diffusion Theory  Program  for  a
Hexagonal-Z Mesh, GA-8547, January 1, 1969.
             M.  R. Wagner,  GAUGE,  A  Two-dimensional Few  Group
Neutron Diffusion-depletion Program for a Uniform Triangular Mesh,
GA-8307, March 1968.
             H. Kraetsch  and M.  R. Wagner,  The Block  Inversion
Method, A  New Approach to Multidimensional  Reactor Calculations,
Transactions of  the American  Nuclear Society,  Vol. 10,  p. 173,
1967.
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11. MACHINE REQUIREMENTS

65K  memory and  10 files  of drum  storage
with a total of 500,000 words capacity
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12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
NESC0380/01 FORTRAN-IV
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13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:   EXEC2.
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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

    It
is not possible to use tape units in place of drum storage.
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15. NAME AND ESTABLISHMENT OF AUTHORS

                 H. Kraetsch and M. R. Wagner
                 General Atomic Company
                 P. O. Box 81608
                 San Diego, California  92138
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16. MATERIAL AVAILABLE
NESC0380/01
File name File description Records
NESC0380_01.001 SOURCE PROGRAM 3462
NESC0380_01.002 SAMPLE PROBLEM DATA 37
NESC0380_01.003 SAMPLE PROBLEM PRINTED OUTPUT 2454
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17. CATEGORIES
  • C. Static Design Studies

Keywords: HTGR reactors, diffusion, few-group, hexagonal configuration, neutron flux, power distribution, three-dimensional.