IAEA0928 COMTA-IIM.

1. NAME OR DESIGNATION OF PROGRAM:  COMTA-IIM.

3. DESCRIPTION OF PROGRAM OR FUNCTION

COMTA-IIM is a program for integrated fuel performance analysis for free standing cladding with ceramic fuel. The program accepts design, manufacturing and operating parameters as input and gives the state of cladding at end of life. In the package supplied, more emphasis is placed on mechanical analysis and the associated convergence requirements.
The package essentially performs 1-dimensional analysis of a thin slice giving triaxial stress and strain values for elastic, thermal  and creep behaviour of the cladding at each of the points in the supplied power history (Time Vs. heat flux).

4. METHOD OF SOLUTION

COMTA can be divided into two parts. viz. thermal and mechanical. The segment performing the thermal analysis  calculates radial temperature distribution across pellet and clad. This also establishes pellet-cladding mechanical interaction which is fed to the mechanical analysis segment.
For mechanical analysis, a thin slice of cladding is analysed as a plain strain problem. Non-linearity arises because of the presence of neutron induced creep and plasticity in the cladding. Convergence problems arising in performing time integration are tackled by having an elaborate subroutine for time step selection and having an alternate convergence scheme. The program has the Newton-Raphson and Variable Metric methods as two different types of non-linear equation solution algorithms.

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

Currently the program cannot take more than five radial nodes across the clad. This can easily be increased by changing a corresponding parameter in the program.

6. TYPICAL RUNNING TIME

For the sample problem supplied, the program  will not take more than 60 seconds on a machine with 0.3 Wheatstone  rating.

NEA-DB executed the two test cases included in this package on a VAX 8810 computer. Required CPU times were: 2.30 seconds (case 1); 2.85 seconds (case 2).

7. UNUSUAL FEATURES OF THE PROGRAM

The program segment COMTA-IIM performs mechanical analysis only. The thermal analysis part has been greatly simplified and incorporated to study the behaviour of a mechanical segment in isolation. Thus any attempt to use the program for a separate data set may lead to erroneous results.

8. RELATED AND AUXILIARY PROGRAMS:

10. REFERENCES

- S. Basu et al.
  COMTA' A Computer Code for Fuel Mechanical and Thermal Analysis
  paper C3/11 in Proceedings of SMIRT-S,
  Berlin, Aug. 1979.
- K.N. Vyas et al.
  Convergence Behaviour of Non-Linear Equation Solvers in Fuel
  Performance Analysis Codes.
  CNS Conference on Numerical Methods in Nuclear Engineering,
  Montreal, Sept. 1983.

- BARC Reactor Projects Division:
  Convergence Scheme for Computer Code COMTA (Code for Mechanical
  and Thermal Analysis)
  (Received November 1987)

11. MACHINE REQUIREMENTS

The program does not exceed 64 KB of total memory space (including data segment and program segment). However any attempt to increase the radial nodes across the clad will increase the total memory requirement beyond 64 KB.

13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED

Developed on PDP- 11/34 under RSX-11/M and currently also running on SINTRAN-III (J) for ND-560 Machine.

VMS V5.0-1 (VAX 8810).

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:

15. NAME AND ESTABLISHMENT OF AUTHORS

          K.N. Vyas and S. Basu
          Reactor Projects Division
          Engg. Hall-7
          Bhabha Atomic Research Centre
          Bombay-400085, India

File name	File description	Records
IAEA0928_01.001	info.file	47
IAEA0928_01.002	COMTA FORTRAN-77 source	1485
IAEA0928_01.003	Sample data 1	11
IAEA0928_01.004	Output of sample case 1	230
IAEA0928_01.005	Sample data 2	11
IAEA0928_01.006	Output of sample case 2	230