NESC0790 NUBOW-2D/INEL.

1. NAME OR DESIGNATION OF PROGRAM:  NUBOW-2D/INEL

3. DESCRIPTION OF PROBLEM OR FUNCTION

This program solves the two- dimensional mechanical equilibrium configuration of a core restraint system, which is subjected to radial temperature and flux gradients, on a time increment basis. At each time increment, the code calculates the irradiation creep and swelling strains for each duct from user-specified creep and swelling correlations. Using the calculated thermal bowing, inelastic bowing and the duct dilation, the corresponding equilibrium forces, beam deflections, total beam displacements, and structural reactivity changes are calculated.

4. METHOD OF SOLUTION

The calculational history is defined by a constant time increment which should be determined from the system peak flux. Each row is represented by one single duct. All the ducts are subdivided into equal number of segments, and each segment is divided into the same number of equal area cells. Linear radial temperature distribution across the segments and flats is assumed. The thermal bow is linearly proportional to temperature difference. Parabolic flux distribution across each duct is assumed. Based on the assumption that constant force acts on the beam during the small time increment, using the cell temperature and fluences and creep and swelling correlations, the creep and swelling strains are calculated for each cell. Then these strains are numerically integrated along each beam to give the beam prebow shape. The new equilibrium forces and deflections are obtained by block relaxation. The structural reactivity changes are calculated by numerical integration along the beam.

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

Maxima of

    25 beam segments
    16 rows
     6 load points
   144 cells
All the ducts are treated as thin shell hexagons, and only the radial direction effects of creep and swelling are considered. The peak fluence increment must be less than or equal to 2.5 x 10**21 n/cm**2 for the purpose of determining the time increment.

6. TYPICAL RUNNING TIME

Running time depends on the complexities of the user-specified input data. Finer subdivisions take more computer time. For a problem with 16 rows, 21 nodes, and 30 cells, approximately 3 seconds are required for each time increment.

7. UNUSUAL FEATURES OF THE PROGRAM:

8. RELATED AND AUXILIARY PROGRAMS

The calculational procedure and the block relaxation method of NUBOW-2D Inelastic are essentially the same as in NUBOW (NESC Abstract 643). Subroutines have been added to calculate time histories of inelastic changes in bowing shapes and forces induced by creep and swelling in reactor fuel assemblies (ducts).

10. REFERENCES:

- B.K. Cha, G.A. McLennan and P.J. Fulford:
NUBOW-2D INELASTIC: A Fortran Program for Static Two-Dimensional Structural
Analysis of Bowed Reactor Cores, Including Effects of Irradiation Creep and
Swelling.  ANL-CT-77-34  (June 1977).

11. MACHINE REQUIREMENTS

250K bytes of storage are used. The program requires a card reader, a line printer, and two disk units for temporary storage of inelastic strain data. If the restart option is desired, another disk or tape unit is used for restart file data.

13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:  OS/370.

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

The program inelastic strain data are stored on FORTRAN logical unit numbers 10 and 12 using DCB=(RECFM=VBS,BLKSIZE=3000). If the restart option is chosen, FORTRAN logical unit 8 is used to hold the restart file. TLEFT, an installation-dependent routine which provides the job time remaining in hundredths of a second, permits the exercise of the restart option when 7 seconds or less remain. In the package a substitute TLEFT returns a constant value. This routine will have to be replaced with an appropriate local routine to implement the restart facility.

15. NAME AND ESTABLISHMENT OF AUTHORS

                 B. K. Cha and G. A. McLennan
                 Components Technology Division
                 Argonne National Laboratory
                 9700 South Cass Avenue
                 Argonne, Illinois  60439

source program
test-case data
report  ANL-CT-77-34  (June 1977)