NEA-0594 SYNTH-C.

1. NAME OR DESIGNATION OF PROGRAM:  SYNTH-C. (SYNTH-C-STEADY and SYNTH-C-TRANS.)

3. DESCRIPTION OF PROBLEM OR FUNCTION

SYNTH-C-STEADY and SYNTH-C- TRANS solve respectively the steady-state and time-dependent few- group neutron diffusion equations in three dimensions x,y,z in the presence of fuel temperature and thermal-hydraulic feedback. The neutron diffusion and delayed precursor equations are approximated by a space-time (z,t) synthesis method with axially discontinuous trial functions. Three thermal-hydraulic and fuel heat transfer models are available viz. COBRA-3C/MIT model, lumped parameter (WIGL) model and adiabatic fuel heat-up model.

4. METHOD OF SOLUTION

The steady-state and time-dependent synthesis equations are solved respectively by the Wielandt's power method and by the theta-difference method (in time), both coupled with a block factorization technique and double precision arithmetic. The thermal-hydraulic model equations are solved by fully implicit fin-  ite differences (WIGL) or explicit-implicit difference techniques with iterations (COBRA-EC/MIT).

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

Except for the few-  group limitation, the programs have no other fixed limitation so the ability to run a problem depends only on the available com- puter storage.

6. TYPICAL RUNNING TIME

The sample problem (2 groups, 1 precursor group, 19 x 19 x 21 mesh points, 4 trial functions), described in the report, took 20 secs. for the steady state calculation and 7 min. for the time-dependent calculation (180 time steps) on an IBM 370/158.

7. UNUSUAL FEATURES OF THE PROGRAM

The complexity of the problem that can be dealt with. For example BWR problems with 2 neutron groups, 1 precursor group, 200 planar regions or channels, 10 axial  regions, 4 trial functions and up to 100 x 100 x 100 mesh points could be run with a storage requirement of about 1000 K bytes and a still reasonable running time.

8. RELATED AND AUXILIARY PROGRAMS

The SQUID-SYN program, which solves the multigroup neutron diffusion equations in two-dimensions (rec- tangular or cylindrical geometry), can be used to generate trial and weight functions that can be tested for linear independence by the GRAMMA program. The LIBGEN program can be used for further pro-  cessing of the library files (collections of trial and weight func-  tions) that are to be fed into the SYNTH programs. All of these programs are described in the reference report quoted in item 10.

10. REFERENCES:

- E. Brega, F. Di Pasquantonio and E. Salina:
  Three-Dimensional Transient Analysis in Thermal Power Reactors: An
  Extensive Comparison Between Finite Difference and Space-Time
  Synthesis Methods
  Reprint Annals of Nuclear Energy, Vol. 5 pp. 117-132
  (Recieved 7 October 1977)
- E. Brega and E. Salina:
  SYNTH-C - A Program for the Neutron and Thermal-Hydraulic Dynamic
  Analysis of Large Power Reactors in Three Space Dimensions
  ENEL-DSR-CRTN N5-19 (December 1979)
- F. Di Pasquantonio, E. Brega and E. Salina:
  The SYNTH Code for Three-Dimensional Static and Transient Analysis
  of LWR Cores
  ENEL-DSR-CRTN N5-22 (April 1980)

11. MACHINE REQUIREMENTS

About 300,000 bytes are required to store the load module of either SYNTH program. This figure can be con- siderably reduced by a suitable overlay organisation, also indicated in the reference report.

Moreover, a labeled COMMON that can be easily modified to fit the remaining part of the available core storage, contains all of the variables with data-dependent dimensions. Five peripheral storage devices (discs or tapes) are needed, of which one is a library of trial functions and another is for input/output of restart data.

13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:  IBM System/ 370, G1 compiler.

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:

15. NAME AND ESTABLISHMENT OF AUTHOR

          E. Brega
          ENEL-CRTN
          Bastioni di Porta Volta 10
          Milan
          Italy.

          E. Salina
          A.R.S. Spa
          Viale Maino 35
          Milan
          Italy.

File name	File description	Records
NEA0594_01.001	INFORMATION	17
NEA0594_01.002	SQUID SOURCE	5151
NEA0594_01.003	SQUID INPUT	228
NEA0594_01.004	SQUID OUTPUT	4858
NEA0594_01.005	GRAMMA SOURCE	952
NEA0594_01.006	GRAMMA INPUT	6
NEA0594_01.007	GRAMMA OUTPUT	269
NEA0594_01.008	LIBGEN SOURCE	726
NEA0594_01.009	LIBGEN INPUT	10
NEA0594_01.010	LIBGEN OUTPUT	719
NEA0594_01.011	STEADY SOURCE	5198
NEA0594_01.012	STEADY INPUT	177
NEA0594_01.013	STEADY OUTPUT	1885
NEA0594_01.014	TRANS SOURCE	6136
NEA0594_01.015	TRANS INPUT	32
NEA0594_01.016	TRANS OUTPUT	7999
NEA0594_01.017	ORIGINAL JCL	148
NEA0594_01.018	NEA JCL	119
NEA0594_01.019	TITIME SOURCE	11