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NEA-0623 LOCA-MARK-2.

LOCA-MARK-2, Fuel Temperature and Clad Temperature in HWR Steam Generator LOCA

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1. NAME OR DESIGNATION OF PROGRAM:  LOCA-MK-2 - A program for calcu- lating fuel and cladding temperatures in SGHWR following a loss- of-coolant accident.
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2. COMPUTERS
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Program name Package id Status Status date
LOCA-MARK-2 NEA-0623/01 Tested 01-MAY-1980

Machines used:

Package ID Orig. computer Test computer
NEA-0623/01 IBM 3033 IBM 3033
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3. DESCRIPTION OF PROBLEM OR FUNCTION

A feature of the Steam Generating Heavy Water Moderated Reactor is the provision of a spray cooling system on which major reliance is placed to limit fuel cladding temperatures during a loss-of-coolant accident.
LOCA-MK-2, which has been written to compute SGHWR fuel temperatures in a loss-of-coolant accident, therefore models conditions in which  blowdown cooling is only of marginal interest and where the major sources of heat removal are spray mechanisms and radiation. LOCA-MK-2 models the fine details of the fuel cluster, and zircaloy  oxidation and radiation.
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4. METHOD OF SOLUTION

The code assumes that heat transfer depends entirely on spray mechanisms and radiation. The heat transfer history of an accident is divided into three parts:

-  Convective heat transfer, terminated by dryout.
-  Low radiative heat transfer.
-  Spray cooling of the cluster.

LOCA-MK-2 performs a 1-D transient conduction calculation for a typical pin of each ring; temperature is found as a function of radius from the centre of the fuel.

The solution of the conduction equation is by an implicit method and is therefore stable for all sizes of time steps.

The variation of neutron flux after the accident is determined from the conventional six precursor group single point kinetics equations.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM:
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6. TYPICAL RUNNING TIME:  A few seconds on the ICL 4/70.
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7. UNUSUAL FEATURES OF THE PROGRAM

Distinctive features that differ from other accident sequence codes such as RELAP-UK are treatment of radiation and detailed modelling of the fuel cluster.
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8. RELATED AND AUXILIARY PROGRAMS:
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9. STATUS
Package ID Status date Status
NEA-0623/01 01-MAY-1980 Tested at NEADB
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10. REFERENCES

- J.D. Matthews, B.R. Gill:
  LOCA-MK-2: A Program for Calculating Fuel and Cladding
  Temperatures in SGHWR Following a Loss-of-Coolant Accident
  AEEW-R 1231 (1979).
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11. MACHINE REQUIREMENTS:  Less than 70 K bytes of core storage.
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12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
NEA-0623/01 FORTRAN-IV
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13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:
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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:
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15. NAME AND ESTABLISHMENT OF AUTHOR

          J. D. Matthews, B. R. Gill
          SGHWR Development Division
          AEE Winfrith
          Dorchester, Dorset
          United Kingdom.
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16. MATERIAL AVAILABLE
NEA-0623/01
File name File description Records
NEA0623_01.001 INFORMATION FILE 12
NEA0623_01.002 SOURCE 782
NEA0623_01.003 INPUT DATA AND JCL 13
NEA0623_01.004 S.P.OUTPUT 947
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17. CATEGORIES
  • G. Radiological Safety, Hazard and Accident Analysis
  • H. Heat Transfer and Fluid Flow

Keywords: cladding, fuel element clusters, fuels, heat transfer, heavy water moderated reactors, loss-of-coolant accident, reactor safety, sprays, temperature, zircaloy.