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NEA-1125 HEXANN-EVALU.

HEXANN-EVALU, Neutron Irradiation of Reactor Pressure Vessels

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1. NAME OR DESIGNATION OF PROGRAM:  HEXANN-EVALU.
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2. COMPUTERS
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Program name Package id Status Status date
HEXANN-EVALU NEA-1125/01 Tested 01-DEC-1993

Machines used:

Package ID Orig. computer Test computer
NEA-1125/01 CDC CYBER 170 CRAY Y-MP
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3. DESCRIPTION OF PROGRAM OR FUNCTION

HEXANN-EVALU calculates the neutron irradiation of a pressure vessel surrounding a nuclear reactor core composed of hexagonal assemblies. The area outside the  core may contain hexagonal shielding assemblies of non-multiplying materials, a core liner and annular material zones.
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4. METHOD OF SOLUTION

The Monte Carlo method is used. The neutrons start at the core boundary with a given distribution in space, angle and energy. The angular distribution is calculated by HEXANN itself  from data describing the spacial distribution of the neutron source  in the core. Survival biasing is used in all collisions. To increase efficiency the following options are included: regionwise importance, Russian roulette, low energy Russian roulette, splitting, path stretching with explicit exponential transform and automatic importance correction.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

30-degree symmetry assumed
Maximum number of energy groups = 30
Maximum group number change in downscattering = 19
No upscattering
Maximum number of materials = 10
Maximum number of cylindrical surfaces = 20
Maximum number of source faces (hexagon faces at edge of core in   30-degree sector)= 20
Vacuum boundary conditions are used at the top, bottom and outer   boundary
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6. TYPICAL RUNNING TIME

About 1,000 seconds on a Cyber 173 for 30,000 neutron histories and 3 response functions. About 10 such runs are needed to accumulate reasonably good statistics.
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7. UNUSUAL FEATURES OF THE PROGRAM

The history tracing and estimation are handled by separate programs (HEXANN and EVALU, respectively). The user specifies those cylindrical surfaces or regions where estimation is to be performed, and every time an assigned surface is crossed, or a free flight or collision is played in an assigned region, a record containing all the information relevant to the event is written on the "History Tape", which passes information from HEXANN to EVALU. EVALU prints either the flux as such (in a number of groups, if desired) or some reaction rate obtained by weighting the flux with an energy-dependent function. Axial and/or azimuthal flux or reaction rate distributions can be obtained (but not distributions varying independently in both the azimuthal and axial coordinates; the dependence on these is assumed to be separable). To get different reaction rates, run EVALU repeatedly.
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8. RELATED AND AUXILIARY PROGRAMS

The program TRIGON-PVND provides the neutron source distribution in the horizontal plane needed to provide the azimuthal position and angular distribution of starters. Cross section data from the BUGLE-80 library are prepared by the program BUGLER. The axial distribution and energy spectrum of neutrons leaving the core can be calculated by any appropriate program.
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9. STATUS
Package ID Status date Status
NEA-1125/01 01-DEC-1993 Screened
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10. REFERENCES:
NEA-1125/01, included references:
- Ivan Lux:
  HEXANN-EVALU - A Monte Carlo Program System for Pressure Vessel
  Neutron Irradiation Calculation
  VTT-TUTK-210 (August 1983).
- Notes on the Use of HAXANN-EVALU.
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11. MACHINE REQUIREMENTS

70 kilowords fast memory + disc or drum storage. Clock required. The maximum length of a file determines how many neutron histories can be treated in a single run. The current version of the program assumes a limit of 96,000 records of 20 words each.
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12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
NEA-1125/01 FORTRAN-IV EXTENDED
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13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:  Standard NOS. Random number routine needed.
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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:
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15. NAME AND ESTABLISHMENT OF AUTHORS

          Ivan LUX
          Nuclear Engineering Laboratory
          Technical Research Centre of Finland
          P.O. Box 169
          SF-00181 Helsinki, Finland

Contact   Frej Wasastjerna
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16. MATERIAL AVAILABLE
NEA-1125/01
File name File description Records
NEA1125_01.001 Information file 78
NEA1125_01.002 JCL for first case (NEADB) 15
NEA1125_01.003 HEXANSC HEXANN in symbolic form 3214
NEA1125_01.004 EVALUSC EVALU in symbolic form 1341
NEA1125_01.005 XLIB26 Cross section lib. 26-group 3121
NEA1125_01.006 HEXTES1 JCL 26-group test case 1 (author) 30
NEA1125_01.007 HEXTES2 JCL 26-group test case 2 (author) 34
NEA1125_01.008 HEXTEST jcl 7-group test case (author) 23
NEA1125_01.009 HEXIN1 HEXANN input 26-group test case 1 103
NEA1125_01.010 HEXIN2 HEXANN input 26-group test case 2 103
NEA1125_01.011 ZHEXTES HEXANN input 7-group test case 122
NEA1125_01.012 EVALDP1 EVALU input dpa eval. test case 1 15
NEA1125_01.013 EVALDP2 EVALU input dpa eval. test case 2 15
NEA1125_01.014 ZEVATES EVALU input dpa eval 7-group t.c 12
NEA1125_01.015 EVALFM1 EVALU input 54Fe(n,p)54Mn case 1 15
NEA1125_01.016 EVALFM2 EVALU input 54Fe(n,p)54Mn case 2 15
NEA1125_01.017 EVALFX1 EVALU input flux eval. case 1 7
NEA1125_01.018 EVALFX2 EVALU input flux eval. case 2 7
NEA1125_01.019 HEXOUT1 Output of first run 2982
NEA1125_01.020 HEXOUT2 Output of second run 378
NEA1125_01.021 HEXOUT Output of 7-group test case 857
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17. CATEGORIES
  • G. Radiological Safety, Hazard and Accident Analysis

Keywords: Monte Carlo method, neutron flux, pressure vessels, reaction rates.