NESC0700 MELT3

1. NAME OR DESIGNATION OF PROGRAM:  MELT3

3. DESCRIPTION OF PROBLEM OR FUNCTION

MELT3 is a multichannel, neutronics, thermal-hydraulics digital computer program developed to investigate the transient behavior of a fast reactor during postulated transient overpower conditions. Reactivity feedback resulting from Doppler broadening, coolant density change and expulsion, bulk core expansion, and fuel movement are explicitly taken into account. The bulk of the modeling detail has been addressed to the in-vessel portion of the reactor plant, although the friction and inertial aspects of up to three separate closed primary loops can be simulated. A wide variety of accident conditions may be investigated. Particular modeling emphasis has, however, been placed on the simulation capabilities required for an unprotected transient overpower accident sequence.

4. METHOD OF SOLUTION

The energy equations are solved by a Crank- Nicholson type implicit scheme. The momentum equations are solved by an iterative implicit scheme.

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

Calculations for up  to 20 channels (e.g., 20 pins representative of subassembly clusters) and 20 axial segments within the fuel region may be performed simultaneously. A total of 10 different axial coolant flow zones having different flow areas (comprising a total of 75 nodes) can be explicitly modeled in the axial direction. Radial heat transfer calculations within each pin axial segment are performed using up to 12 radial fuel nodes (including one surface node), 3 cladding nodes (including inner and outer surface nodes), a coolant  node, and a structural node.

6. TYPICAL RUNNING TIME

Typical CDC7600 run times for cases using essentially full geometric detail are approximately 0.6 second per channel for steady-state calculations, 0.2 second per channel per time-step up to the time of cladding failure, and 0.4 second per channel per time-step after cladding failure. These time estimates appear to increase by about a factor of two for the CDC CYBER74.

7. UNUSUAL FEATURES OF THE PROGRAM

A zero neutron lifetime approximation is available to allow large time-steps to be taken during slow-moving portions of the transient. Protection is included, however, to assure that failure criteria levels are not overshot.

8. RELATED AND AUXILIARY PROGRAMS

MELT3 is a continuation of the MELT code series with MELT1 and MELT2 being its predecessors. MELT3 has significant modeling improvements over the two previous codes, particularly with regard to system hydraulics. It also has incorporated as a subroutine, the SIEX code (NESC Abstract 673) for  steady-state fuel pin simulation.

10. REFERENCES

- D.S. Dutt and R.B. Baker:
  SIEX, A Correlated Code for the Prediction of Liquid Metal Fast
  Breeder  Reactor (LMFBR) Fuel Performance
  HEDL-TME 74-55 (September 1974).

- Alan E. Waltar, et al.:
  MELT-III, A Neutronics, Thermal-hydraulics Computer Program for
  Fast Reactor Safety Analysis
  HEDL-TME 74-47 (December 1974).

11. MACHINE REQUIREMENTS

With dummy plot routines, the steady-state program requires 111,000 (octal) words of storage and 4 logical units. The transient program requires 161,000 (octal) words of storage and approximately 300K (decimal) words of peripheral storage on 9 logical units for wrapup and plotting.

13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:  SCOPE 3.4 (CDC6600,CYBER74), SCOPE 2.1 (CDC7600).

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

  File
STEADY, which is written by the steady-state program, is mandatory input for the transient program. The transient program requires the  FORTRAN Extended Record Manager File Processing System. Plotting capability is provided to supplement the printed output, but plots are not necessary for MELT3 operation. The sample problems may be executed while using the dummy CalComp plot routines supplied with the package. A more efficient alternative is to supply dummy subroutines for PLOT, PLOTS, and DRAW in the steady-state program, and a dummy subroutine for XPLOTX in the transient program. Both the steady-state and the transient program assume that the operating system will zero the memory at load time.

15. NAME AND ESTABLISHMENT OF AUTHORS

                 Alan E. Waltar, et al.
                 Hanford Engineering Development Laboratory
                 Westinghouse Hanford Company
                 Richland, Washington  99352
                 Richard J. Shields
                 Computer Sciences Corporation
                 Richland, Washington  99352

File name	File description	Records
NESC0700_01.001	INFORMATION	5
NESC0700_01.002	SOURCE PROG. FOR STEADY STATE CALCULATION	3173
NESC0700_01.003	SOURCE PROG. FOR TRANSIENT CALCULATION	8560
NESC0700_01.004	DUMMY PLOT ROUTINES	45
NESC0700_01.005	SAMPLE INPUT FOR STEADY STATE CALCULATION	190
NESC0700_01.006	SAMPLE INPUT FOR TRANSIENT CALCULATION	80
NESC0700_01.007	SAMPLE INPUT FOR RESTART CALCULATION	40
NESC0700_01.008	JCL	30
NESC0700_01.009	PRINTED OUTPUT FOR STEADY STATE CALCULATION	2350
NESC0700_01.010	PRINTED OUTPUT FOR TRANSIENT CALCULATION	2297
NESC0700_01.011	PRINTED OUTPUT FOR RESTART CALCULATION	2279