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NESC0508 MUCHA1/MUCHA2

MUCHA1, Fuel Rod Pair Thermohydraulics During LOCA and ECCSA for LWR
MUCHA2, Primary Coolant Thermohydraulics During LOCA and ECCS for LWR

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1. NAME OR DESIGNATION OF PROGRAM:  MUCHA1/MUCHA2
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2. COMPUTERS
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Program name Package id Status Status date
MUCHA1/MUCHA2 NESC0508/01 Tested 01-JUL-1975

Machines used:

Package ID Orig. computer Test computer
NESC0508/01 IBM 370 series IBM 370 series
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3. DESCRIPTION OF PROBLEM OR FUNCTION

MUCHA1 predicts the thermal and hydraulic behavior of any two reactor fuel rods and their associated parallel flow channels during a loss-of-coolant accident using as boundary conditions plenum fluid conditions determined by MUCHA2 or  a system-oriented code. MUCHA2 predicts the thermal and hydraulic behavior of the primary coolant within the reactor pressure vessel during a loss-of-coolant accident. The heated core is represented by two equivalent fuel rods and their associated parallel flow channels. A plenum model has been developed to predict the upper and lower plenum fluid conditions throughout the accident sequence for use as boundary conditions for the parallel core channels.
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4. METHOD OF SOLUTION

In MUCHA1 an explicit, finite-difference technique is used to solve the conservation equations describing the fluid behavior in the parallel core channels. Fluid thermodynamic properties are determined from property tables using an explicit, finite-difference technique. In MUCHA2 an explicit finite-difference technique is used to solve the conservation equations describing the fluid behavior in parallel core channels and plena. Fluid thermodynamic properties are determined from property tables incorporated in the code. Heat conduction in the fuel rod is determined using an explicit, finite-difference technique.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

In MUCHA1 the two fuel rods can be represented by up to a total of 15 radial nodes. Each fuel rod and its associated flow channel may be represented by  up to 12 axial segments. MUCHA2 applies the same restrictions to each pair of equivalent fuel rods.
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6. TYPICAL RUNNING TIME

MUCHA1 running time varies between 200 to 300 times real time, using 2-foot axial segments in each flow channel. Doubling the number of axial segments will increase the running time by approximately a factor of 4. MUCHA2 running time varies between 200 to 400 times real time, using 2-foot axial segments in each flow channel. Doubling the number of axial segments will increase the running time by approximately a factor of 4.
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7. UNUSUAL FEATURES OF THE PROGRAM

With MUCHA1 the thermal and hydraulic behavior of any two fuel rods and their associated flow channels can be predicted during all phases of a loss-of-coolant accident. MUCHA2 provides a detailed description of the core and plenum thermal-hydraulic behavior during all phases of a loss-of- coolant accident, including the emergency core coolant injection phase.
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8. RELATED AND AUXILIARY PROGRAMS

MUCHA1 requires as input time- dependent  plenum  fluid  conditions determined  by  MUCHA2  or  a
system-oriented code.
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9. STATUS
Package ID Status date Status
NESC0508/01 01-JUL-1975 Tested at NEADB
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10. REFERENCES:
NESC0508/01, included references:
- R.A. Cudnik:
  ECCSA and MUCHA - Computer Codes for the Analysis of Emergency
  Core Cooling Systems
  BMI-1916 (September 1971).
- Battelle 6400 Programming Bulletin, No. 11,
  UNILIN (March 21, 1967).
- Battelle 6400 Programming Bulletin, No. 12,
  BILIN1 (March 24, 1967).
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11. MACHINE REQUIREMENTS

MUCHA1 requires 120K (octal) memory and one tape for restart capability. MUCHA2 requires 120K (octal) memory, one tape for restart capability, and one tape for storing plenum boundary conditions.
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12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
NESC0508/01 FORTRAN-IV
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13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:   SCOPE 3.3.
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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

MUCHA1
and MUCHA2 require the use of CDC6400 FORTRAN function subprograms UNILIN and BILIN1. UNILIN performs linear interpolation from a table of values of y versus x. BILIN1 performs linear interpolation from a table of values of z versus x and y. MUCHA1 calls UNILIN from HTCHG  and MUCHA2 calls it from HTCHG, FLUID, and PLENA. MUCHA1 calls BILIN1 from PHISQ and MUCHA2 also calls it from PHISQ.
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15. NAME AND ESTABLISHMENT OF AUTHORS

                 Ronald A. Cudnik
                 Columbus Laboratories
                 Battelle Memorial Institute
                 505 King Avenue
                 Columbus, Ohio  43201
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16. MATERIAL AVAILABLE
NESC0508/01
File name File description Records
NESC0508_01.001 DATA LIBRARY (BCD) 1829
NESC0508_01.002 MUCHA1 SOURCE PROGRAM (EBCDIC) F4 1931
NESC0508_01.003 MUCHA1 SAMPLE PROBLEM DATA 435
NESC0508_01.004 MUCHA1 JCL 1
NESC0508_01.005 MUCHA1 SAMPLE PROBLEM PRINTED OUTPUT 1819
NESC0508_01.006 MUCHA2 SOURCE PROGRAM (EBCDIC) F4 3191
NESC0508_01.007 MUCHA2 SAMPLE PROBLEM DATA 68
NESC0508_01.008 MUCHA2 JCL 1
NESC0508_01.009 MUCHA2 SAMPLE PROBLEM PRINTED OUTPUT 961
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17. CATEGORIES
  • G. Radiological Safety, Hazard and Accident Analysis

Keywords: accidents, coolants, heat transfer, reactor safety, thermodynamics, water.