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NEA-0808 DIFFUSION-ACE.

DIFFUSION-ACE, 3-D Neutron Diffusion by Leakage Iteration Method

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1. NAME OR DESIGNATION OF PROGRAM:  DIFFUSION-ACE.
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2. COMPUTERS
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Program name Package id Status Status date
DIFFUSION-ACE NEA-0808/01 Tested 03-JAN-1986

Machines used:

Package ID Orig. computer Test computer
NEA-0808/01 FACOM M-200 IBM 3081
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3. DESCRIPTION OF PROBLEM OR FUNCTION:  Three dimensional neutron diffusion.
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4. METHOD OF SOLUTION

Leakage iteration method is applied. For this method, a reactor is divided into several layers along the Z axis and into several rectangular channels perpendicular to the x-y plane.

A one-dimensional neutron flux calculation is performed for each channel with the radial leakage coefficient. A two-dimensional neutron flux calculation is then made for each layer with the axial  leakage determined from the one-dimensional calculation.

The one- and two-dimensional leakage will be iterated until the consistency is attained between the two.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

Number of energy groups is fixed to be 2 or 3.
Maximum number of channels along X axis is 10.
Maximum number of channels along Y axis is 10.
Maximum number of blocks along Z axis is 12.
Maximum number of channels at which one-dimensional calculation is performed is 79.
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6. TYPICAL RUNNING TIME

Typical running time of the example case of JPDR quater core (72/4 assemblies) is 150 sec CPU with the computer  FACOM-M200.
NEA-0808/01
NEA-DB has tested the program on IBM 3081D. To execute  the test case included in the package required 202 seconds of CPU time.
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7. UNUSUAL FEATURES OF THE PROGRAM

In this program, the leakage iterative method is applied which has the following characteristics: a. A fine-mesh difference approximation technique is applied only  to the channels and layers. Therefore, it is not necessary to  calculate the neutron fluxes at all fine-mesh points in the core     and thus the computer time is reduced.
If the block which is formed by a channel and a layer, is a  12 cm cube and the mesh width is 2 cm, the number of fine-mesh     points is 6x6x6=216.
In the present method, however, the number of mesh points is  6+(6x6)=42, that is about one-fifth of the former. The terms  connecting the channel and layer calculations are only the  neutron leakage and the neutron source, which reduce the     computer memory required.

b. Since the neutron leakage from a block is calculated by a fine-  mesh difference approximation, the discretization error is     minimized.

c. When only one fine-mesh point is located in each block, this  method becomes the same as a fine-mesh difference approximation.  In this case, the iterative scheme corresponds to one of the  variants of the Peaceman-Rachford iterative method. Therefore,  it is possible to establish the condition under which the  consistency is achieved between the axial and radial leakages in  the same manner as ADI (alternative direction implicit iterative  method due to Peaceman and Rachford), and it is easy to compare  the results with those obtained from conventional fine-mesh  difference approximation methods. The computer code can be used     for calculating both the collapsed flux and the fine-mesh flux.
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8. RELATED AND AUXILIARY PROGRAMS

CELL-ACE: Burnup dependent cell constants calculation program for LWR.
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9. STATUS
Package ID Status date Status
NEA-0808/01 03-JAN-1986 Tested at NEADB
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10. REFERENCES

- Y. Naito, M. Maekawa and K. Shibuya:
  "A Leakage Iterative Method for Solving the Three-Dimensional
   Neutron Diffusion Equation"
  Nucl. Sci. Eng. 58 (1975).
- Y. Naito, M. Maekawa and M. Toba:
  "Computer code system CELL-ACE for Burn-up Dependent Averaged Few
   Group Constants Over the Cell in LWR"
  JAERI-M 7544 (1978).
NEA-0808/01, included references:
- Y. Naito, M. Maekawa and K. Shibuya:
  A Three-Dimensional Neutron Diffusion Calculation Code
  DIFFUSION-ACE
  JAERI 1262 (July, 1979).
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11. MACHINE REQUIREMENTS:
NEA-0808/01
To run the test case on IBM 3081D, 792 Kbytes of main storage are required.
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12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
NEA-0808/01 FORTRAN-IV
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13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:  OS - IV F4.
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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:
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15. NAME AND ESTABLISHMENT OF AUTHOR

          Yoshitaka Naito
          Division of Reactor Safety Evaluation Laboratory
          Japan Atomic Energy Research Institute
          Tokai-Mura
          Naka-gun
          Ibaraki-ken
          Japan
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16. MATERIAL AVAILABLE
NEA-0808/01
File name File description Records
NEA0808_01.003 INFORMATION FILE 81
NEA0808_01.004 DIFFUSION-ACE JCL USED IN TESTING 71
NEA0808_01.005 DIFFUSION-ACE FORTRAN SOURCE 4779
NEA0808_01.006 SAMPLE PROBLEM INPUT 55
NEA0808_01.007 PRINTED OUTPUT FOR SAMPLE PROBLEM 2693
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17. CATEGORIES
  • C. Static Design Studies

Keywords: diffusion equations, iterative methods, neutron diffusion equation, neutron flux, three-dimensional.