last modified: 20-OCT-1982 | catalog | categories | new | search |

NEA-0821 RELAP/REFLA(MOD0).

RELAP/REFLA, Core Reflooding During PWR LOCA

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1. NAME OR DESIGNATION OF PROGRAM:  RELAP/REFLA(MOD0).
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2. COMPUTERS
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Program name Package id Status Status date
RELAP/REFLA NEA-0821/01 Tested 20-OCT-1982

Machines used:

Package ID Orig. computer Test computer
NEA-0821/01 IBM 3033 IBM 3033
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3. DESCRIPTION OF PROBLEM OR FUNCTION

RELAP/REFLA has been developed  to describe the behaviour of the reflooding core during the postulated loss-of-coolant accident of pressurized water reactors. The program calculates fluid conditions in the system such as flow,  pressure, mass inventory, and quality; thermal conditions in the core such as surface temperatures, quench front propagation and heat fluxes. Temperatures and heat fluxes are also calculated for dissipating elements. In addition to describing reflood phenomena in PWRs, the program is sufficiently versatile to describe transients in experimental test facilities which is simulating the PWR reflood.
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4. METHOD OF SOLUTION

User must define the geometric features of the  system to be analyzed as well as an appropriate set of initial conditions at the beginning of the reflood, i.e., at BOCREC. Initial conditions to be specified include the following: axial distribution in the core, heat generation rate, system pressure, core inlet subcooling and steam generator secondary conditions. ECC injection rate, decay power and containment pressure history are time dependent boundary conditions to be specified. RELAP/REFLA then solves the thermal-hydraulics in the reflooding core and other parts of the reactor system. In the latter calculation, an integral form of the fluid conservation equations and state equations applied to each user-defined control volume are solved. Core inlet conditions derived from the system calculation are utilized as boundary conditions in core calculations. Thermal and hydraulic properties of the core are brought back into the system calculation, so that feedback from the system can affect the reflood process.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

Maxima of
9  minor edit variables
20  time-step cards
20  trip control cards
70  junctions (flow paths) between volumes
5  bubble parameter sets
5  time-dependent volume descriptions on cards
12  pumps
50  control volumes
10  check valve types
5  normalized leak-area-versus-time curves
20  fill system curves
50  heat slabs
20  heat slab geometries
7  heat slab materials

Fixed modes:
1 control volume each for heated core, downcomer lower plenum and     upper plenum
10  core section heat slabs
90  axial fine meshes in core
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6. TYPICAL RUNNING TIME

To model 3 to 5 minutes real time of a reflooding problem for a PWR consisting of 25 to 35 fluid volumes requires from 0.5 to 2 hours or more of FACOM-M200 CP time.
NEA-0821/01
NEA-DB executed the test case on IBM 3033 in 320 sec.
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7. UNUSUAL FEATURES OF THE PROGRAM

RELAP4's fully-implicit integration technique is maintained for the loop calculation, but the explicit scheme is applied for the core thermal-hydraulic analysis and coupling between core and loop calculation. The following features of the RELAP4/MOD3 are also preserved without modification: heat conduction in materials, the moment flux term in  the hydraulic equations and a pump model with inertia and friction.  The program also provides special model for the broken cold leg of a PWR in a postulated loss-of-coolant accident.
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8. RELATED AND AUXILIARY PROGRAMS

A plotter program for the RELAP4 codes, PLOTR4, can be used to plot some of the variables calculated  in the RELAP part of RELAP/REFLA. A program, with extended capability to plot variables from the REFLA part, i.e. detailed core reflood information, is under preparation for release.
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9. STATUS
Package ID Status date Status
NEA-0821/01 20-OCT-1982 Tested at NEADB
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10. REFERENCES

- Y. Murao, "An Analytical Study of the Thermo-Hydrodynamic
  Behavior of the Reflood Phase During a LOCA", KFK-2545 (1977).
NEA-0821/01, included references:
- K. Fujiki, T. Shimooke and Y. Murao:
  RELAP/REFLA (MOD0): A System Reflooding Analysis Computer Program.
JAERI-M 9397 (March 1981).
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11. MACHINE REQUIREMENTS:  1100 kbytes (on FACOM-M200).
1200 kbytes on IBM 3033.
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12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
NEA-0821/01 FORTRAN-IV
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13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:
OS-IV (FACOM-M200). OS/033 (IBM 3033).
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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

The compilation region is about 768 kbytes. The OPT = 2 option should be invoked.
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15. NAME AND ESTABLISHMENT OF AUTHOR

          K. Fujiki, T. Shimooke* and Y. Murao
          Japan Atomic Energy Research Institute
          Tokai-mura, Ibaraki-ken
          Japan

       *  Nuclear Power Engineering Test Center
          Institute for Nuclear Safety
          Mita Kokusai Building, 1-4-28, Mita
          Minato-ku, Tokyo
          Japan
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16. MATERIAL AVAILABLE
NEA-0821/01
File name File description Records
NEA0821_01.001 RELAP/REFLA INFORMATION 94
NEA0821_01.002 RELAP/REFLA SOURCE PART I (FORTRAN-4) 15008
NEA0821_01.003 RELAP/REFLA SOURCE PART II (FORTRAN-4) 15004
NEA0821_01.004 RELAP/REFLA SOURCE PART III (FORTRAN-4) 8812
NEA0821_01.005 IAND, IOK, CLOCKM ROUTINES (FORTRAN-4) 14
NEA0821_01.006 SETB99 (REPLACEMENT FOR ENCODE) (ASSEMBLER) 100
NEA0821_01.007 ICLOCK (ASSEMBLER) 92
NEA0821_01.008 INPUT DATA FOR TEST CASE 338
NEA0821_01.009 OUTPUT OF TEST CASE 3431
NEA0821_01.010 JCL FOR TEST CASE 88
NEA0821_01.011 STEAM TABLE (BINARY) 79
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17. CATEGORIES
  • G. Radiological Safety, Hazard and Accident Analysis
  • H. Heat Transfer and Fluid Flow

Keywords: ECCS, feedback, flow models, fluid flow, loss-of-coolant accident, pwr reactors, reflooding.