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 1. Name of Experiment:
    VENUS-3 LWR-PVS Benchmark Experiment (1988)

 2. Purpose and Phenomena Tested:
    Mock-up of the pressure vessel internals representative of a 3 Loop Westinghouse

    Methods to reduce Lead Factor and to improve its prediction were investigated,
    taking into account axial source distribution. As proposed for some early built
    reactors, at the most critical corners of the core periphery part of the fuel
    length was replaced by the Partial Length Shielded Assemblies thus reducing the
    Lead Factor at the level of the pressure vessel horizontal welding.
    Pin-to-pin pitch was typical for 17x17 PWR fuel assemblies. 

    The LWR-PVS-BENCHMARK experiment in VENUS was aimed at validating the analytical 
    methods needed to predict the azimuthal variation of the fluence in the pressure

 3. Description of the Source and Experimental Configuration:
    The VENUS Critical Facility is a zero power reactor located at CEN/SCK, Mol

    The Partial Length Shielded Assemblies were loaded at the corners of the 
    core periphery. The shielded part was obtained by replacing part of the 
    fuel length by a stainless steel rod. For benchmarking this improvement, 
    the VENUS-3 core has been built with 3/0-SS rods at the periphery (the 
    3/0-SS rods were made of half a length of stainless steel and half a length
    of 3.3 % U-235 enriched UO2 fuel).

    The core is made of 16 "15x15" subassemblies, instead of "17x17" ones 
    (the pin-to-pin pitch remains typical of the "17x17" subassembly). 

    The second water gap and the pressure vessel are not simulated; a validation
    of the calculation up to the thermal shield was considered as acceptable;
    the complete simulation in the radial direction was indeed investigated in
    a slab geometry with the PCA mock-up. 

    Except for the baffle- and the reflector minimum-thickness, the thicknesses 
    have been somewhat reduced to fit the VENUS geometry.

    The angular shape of the core barrel is such that both quadrant and 
    octagonal symmetries are achieved with acceptable reflecting conditions 
    (in stainless steel) at 0, 45 and 90 respectively. 

    The angular shape of the thermal shield, so-called Neutron Pad was limited 
    by the available space (it is moreover removable); the quadrant and octagonal 
    symmetries are also achieved with reflecting conditions in water at 0 and 90 
    and with reflecting conditions in stainless at 45. This geometry was moreover 
    considered as representative of some BABCOCK & WILCOX designs. 

    The exact dimensions and the material compositions are given in ven3-exp.htm.
    The data were taken from [6].

    The power distributions are measured precisely through gamma activity
    measurements at the measurement positions shown on ven3-f7.gif.
    The relative uncertainty of the neutron fission source with regard to absolute
    power is below 4% and the uncertainty of source space distribution is between
    1.5% and 4%. The missing points were determined through interpolation procedure
    RECOG-ORNL performed at the NEA. The interpolation procedure is described in [7].
    The input and output data for the RECOG code are also provided here, see e.g.
    recog1.inp and recog1.out. The complete 3-D map of the neutron source power
    distribution is given in venus3.src. The corresponding uncertainty estimations,
    defined as a difference between the measured values and those calculated by
    the RECOG code, are included in venus3.err.

    The reference measured fission rate is 8.845E9 (+-4%) fissions/sec/pin/quadrant
    and should be used as a multiplication factor for converting the provided
    normalised 3D neutron source to the source at 100% power( the total fission
    rate value per quadrant was obtained from absolute measurements at several
    locations using U-235 miniature fission chambers; this measurement yielded a
    value of 5.652E12 fissions per second per core quadrant which then was divided
    by 639 pins per quadrant yielding 8.845E9 fissions/sec/pin/quadrant).

 4. Measurement System and Uncertainties:
    Measurement locations: the 21 and 45 angles, which correspond to the 
    maximum - and minimum fast fluxes respectively, were provided with 
    experimental holes. In particular, access holes were accommodated at 21 and 
    at the centre with a view to performing neutron- and gamma-spectrometry. 
    Detectors used: Ni-58(n,p), In-115(n,n') and Al-27(n,alpha) reaction rates were
    measured at several points in the reactor. The measurement positions and the 
    corresponding results are given in venus3.res and r_rates.xls, expressed in
    terms of the measured reaction rates. This was preferred to equivalent fission
    fluxes since involving only (or to higher degree) the measured values. 

    If preferred the equivalent fission fluxes can be found in [9] and [11]. Note 
    however that the equivalent fission fluxes were derived by dividing the reaction
    rates by the fission averaged detector cross-sections measured at MOL (see
    report of Maerker/ORNL [12]):

    Ni-58(n,p): 0.1085 b
    In-115(n,n'): 0.1903 b
    Al-27(n,alpha): 0.706E-3 b

    The above values were used for all the measurement positions in the VENUS-3

    The literature cites the relative uncertainty of the neutron fission source with
    regard to absolute power below 4% and the source space distribution between 1.5%
    and 4%. The relative uncertainty of the individual measured reaction rates is
    given as 3% and the estimated composite of all measurement uncertainties of the
    fission equivalent fluxes is below 5%. However the information related to the
    dosimeter activity measurements is not sufficient.

 5. Description of Results and Analysis:
    Calculations were performed by the ANISN, DORT, TORT and MCNP-4 codes. The
    analyses performed in the scope of the NEA Nuclear Science Committee organised
    blind benchmark intercomparison are described in details in [9] and [10]. The
    following computational models using TORT and MCNP4B inputs are included here:

    - mcnp4b.inp: MCNP4B input for VENUS-3, provided by J. Marian, Instituto de
      Fusion Nuclear (DENIM), Madrid, Spain.
    - gipv3.inp, tortv3.inp: input data for the GIP cross-section preparation
      (using BUGLE-96 ENDF/B-VI data, not provided here) and TORT 3D transport
      calculation, prepared at NEA.
    - gip-enea.inp, tort_rtz.inp, tort_xyz.inp: input data for GIP (using BUGLE-96
      ENDF/B-VI cross-sections, not provided here), TORT r-theta-z and TORT xyz
      calculations, provided by M. Pescarini et al., ENEA Bologna, Italy.

    The cross-section sensitivity and uncertainty analysis using the SUSD3D code to
    evaluate the neutron flux uncertainties is described in [7] and [8]. 

 6. Special Features:

 7. Author/Organizer
    Experiment and analysis:
    L. Leenders, A. Fabry, et al.
    SCK-CEN, Belgium

    Compiler of data for Sinbad:
    I. Kodeli
    OECD/NEA, 12 bd. des Iles,
    92130 Issy les Moulineaux, France
    e-mail: ivo.kodeli@oecd.org

    Reviewer of compiled data:

 8. Availability:

 9. References:
    [1] LWR Pressure Vessel Surveillance Dosimetry Improvement Program Review 
        Meeting, NBS, Maryland, Oct.26-30, 1981: Exploratory calculations
        carried out at WESTINGHOUSE, S. ANDERSON in cooperation with 
        G. GUTHRIE (HEDL).  
    [2] A. FABRY, VENUS-3 PLSA Conceptual Design Considerations, CEN/SCK Note 
        AF/sa 380/87-02, Feb.2, 1987
    [3] Design Studies of VENUS-3, a Benchmark Experiments of PLSA calculational
        procedures to be performed in the VENUS critical Facility at Mol.  
    [4] LWR Pressure Vessel Surveillance Dosimetry Program "Activities, Status
        and Scheduling", March 29-April 2, 1982.
    [5] M. L. Williams et al., "Calculation of the Neutron Source Distribution 
        in the VENUS PWR Mockup Experiment," Proceedings of ehe Fifth 
        ASTM-EURATOM Symposium on Reactor Dosimetry, Volume 2, 711-718, 
        Geesthacht, F.R.G., September 24-28, 1984. 
    [6] L. Leenders, LWR-PVS Benchmark Experiment VENUS-3, Core description 
        and Qualification, FCP/VEN/01, SCK/CEN, September 1, 1988. 
    [7] I.Kodeli, E. Sartori, Analysis of VENUS-3 Benchmark Experiment, 
        Proc. Reg. Meeting on Nuclear Energy in Central Europe, Catez, Slovenia
        (Sept. 7-10, 1998)
    [8] I. Kodeli, Multidimensional Deterministic Nuclear Data Sensitivity
        and Uncertainty Code System, Method and Application, 
        Nucl. Sci. Eng., 138, 45-66 (2001)
    [9] Prediction of Neutron Embrittlement in the Reactor Pressure Vessel,
        OECD/NEA report 2000
    [10] M. Pescarini, R. Orsi, M.G. Borgia, T. Martinelli, ENEA Nuclear Data
         Centre Neutron Transport Analysis of the VENUS-3 Shielding Benchmark
         Experiment, Report KT-SCG 00013 (2001)
    [11] Bok-Ja Moon, VENUS-3 PWR UO2 Core 3-Dimensional Benchmark Experiment,
         IRPhE Project Compilation
    [12] R. E. Maerker, Analysis of the VENUS-3 Experiments, NUREG/CR-5338 
         ORNL/TM-11106, Oak Ridge National Laboratory, August 1989.

10. Data and Format:

 FILE  FILENAME                               bytes  Description                                           
 ---- ------------   ------- ------------------------------------------------ 
  1   ven3-abs.htm    14,579 This information file                                 
  2   ven3-exp.htm    42,620 Description of Experiment & material compositions     
  3   venus3.src     106,782 VENUS3 Neutron Source Distribution                    
  4   venus3.err     106,799 Neutron Source Uncertainty Information                
  5   venus3.res      19,048 Measured Reaction Rates                               
  6   r_rates.xls     43,008 Measured Reaction Rates                               
  7   mcnp4b.inp     204,478 MCNP4B input (provided by J. Marian, DENIM)           
  8   gipv3.inp       11,442 GIP Input for XS Preparation (prepared at NEA)        
  9   tortv3.inp      96,500 TORT Input for 3D Calculation (prepared at NEA)       
 10   gip-enea.inp    38.560 Input for GIP (provided by M.Pescarini et al., ENEA)  
 11   tort_xyz.inp   577,080 Input for TORT xyz Calculation (provided by ENEA)     
 12   tort_rtz.inp 1,535,873 Input for TORT r-theta-z Calc. (provided by ENEA)     
 13   recog1.inp      30,403 RECOG Input for Source Interpolation (Ax.level 1)          
 14   recog1.out     141,053 RECOG Output -  Source Interpolation (Ax.level 1)          
 15   recog2.inp      30,403 RECOG Input for Source Interpolation (Ax.level 2)          
 16   recog2.out     141,053 RECOG Output -  Source Interpolation (Ax.level 2)          
 17   recog3.inp      30,403 RECOG Input for Source Interpolation (Ax.level 3)          
 18   recog3.out     141,032 RECOG Output -  Source Interpolation (Ax.level 3)          
 19   ven3-f1.gif     53,749 Fig. 1: Vertical cross section of VENUS3 facility     
 20   ven3-f2.gif     87,408 Fig. 2: Core description (horizontal cross section)   
 21   ven3-f3.gif     62,764 Fig. 3: Top view of VENUS core                        
 22   ven3-f4.gif     53,398 Fig. 4: Vertical cross sectional view of VENUS3 core  
 23   ven3-f5.gif     55,325 Fig. 5: VENUS3 model (horizontal cross section)       
 24   ven3-f6.gif     75,050 Fig. 6: VENUS3 model (vertical cross section)         
 25   ven3-f7.gif     14,520 Fig. 7: xy coordinates of measured power distribution 
 26   venus3-6.pdf   934,625 Reference 6                                            
 27   catez98.pdf    356,653 Reference 7                                           
 28   nea2128.pdf  2,949,681 Reference 9                                           
 29   enea.pdf     2,768,257 Reference 10                                          

    Figures are included in GIF digitized page image form.

SINBAD Benchmark Generation Date: 02/2004
SINBAD Benchmark Last Update: 02/2004