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NAÏADE 1 Graphite Benchmark (60cm)

 1. Name of Experiment: 
    Fontenay aux Roses 60cm NAÏADE 1 Graphite Benchmark

 2. Purpose and Phenomena Tested: 
    Determination of the fission neutron transport in graphite for penetration
    up to 50 cm for the fast neutrons and up to 120 cm for the thermal neutrons.

 3. Description of the Source and Experimental Configuration: 
    The source is a fission plate irradiated by a beam of purely thermal neutrons
    coming from the graphite reflector of the ZOE heavy water reactor located in
    France at Fontenay aux Roses. The plate is 1 square meter and the thickness
    of the fissile part is 2 cm. It consists of 9 square tiles 0.333 m along the
    side, made of natural uranium claded with 1 mm of aluminum. Behind the fission
    plate, which generates fission neutrons, there is a large experimental area
    (27 cubic meter) in which the graphite block is placed. A boral screen
    separated the fission plate from the experimental area to avoid thermal
    neutron backscattering. The graphite block thickness was 140 cm and its
    section was 2.00m x 2.00m enclosed in a steel frame 1 cm in thickness and
    surrounded by a concrete shield.

    The absolute fission neutron source distribution is determined by Monte Carlo
    calculation (TRIPOLI 4) using the thermal neutron flux measurements (Mn-55)
    for the source term. This determination take into account all fissions (U-235
    and U-238) provided by the neutron diffusions in the converter itself, in
    structures and in the mock-up (sub critical system with a source of thermal
    neutrons). In this experiment, the diaphragm diameter was 60 cm. In the
    graphite block a central hole of diameter 5cm can be stopped up with graphite
    plugs of various thicknesses; the irradiated dosimeters are positioned
    between the plugs.

 4. Measurement System and Uncertainties: 
    The following detectors were used:

    1. S-32(n,p) 
    2. Rh-103(n,n’) 
    3. P-31(n,p) (2 sets of measurements)
    4. 3 sets of measurements with silicon diodes (WIGNER effect)
    5. Mn-55(n,gamma) under cadmium
    6. Mn-55(n,gamma) (bare metal)
    7. 2 sets of measurements using Au-197(n,gamma) under cadmium, one at short
       distance, the other at longer distance with overlap
    8. 2 sets of measurements using the In-115(n,gamma) under cadmium.

    All dosimeters were calibrated in well known fluxes depending on their
    characteristics: Maxwellian thermal flux at 27°C in a reference block,
    fission spectrum with correction tacking into account the diffusion effects
    altering slightly the pure fission spectrum, constant flux per unit of

    The graphite specific gravity was 1.65 g/cm3. Measurements were carried out
    to determine the absorption cross-section for thermal neutrons by the
    graphite used in this experiment. 
    The precision of the fission plate power varies between 1% when the measurements
    are made close together in time (a few days) and 5% when the measurements are
    separated by several months. During the dosimeter irradiation, the observed
    stability is (delta P)/P = 0.5%. The dosimeter position uncertainty estimated
    by the experimental team itself is ±0.1cm.

    Note of the data compiler:
    It is possible to provide an estimation of the total dispersion (reactor
    power, detector position and calibration, counting) of several conventional
    fluxes because some measurements have been made during successive irradiations
    at the same location and for the same detector (P-31, Silicon diodes, In-115/Cd).
    We found:
    - Total dispersion on P-31: ±7.5%
    - Total dispersion on silicon measurements ±4.2%
    - For the In-115/Cd dosimeter, 80% of the measurements lead to a dispersion
      less than ±3% and one measurement gives ±22%.

 5. Description of Results and Analysis: 
    All results are expressed in conventional fluxes. (Equivalent fission flux,
    flux per unit of lethargy, equivalent thermal flux at 2200m/s). The
    corresponding mean cross section or integral of resonance are given. The
    measured experimental results are given on the converter axis for several
    distances. A calibrated dosimeter reassessment resulting from the nuclear
    data improvements was made recently (2003-2004) and published.

    The interpretation using the French CEA Monte-Carlo code TRIPOLI 4 was made
    on this graphite benchmark. A background noise evaluation was also determined
    using at the same time TRIPOLI 4 calculations and fast and epithermal neutron
    flux measurements without converter plate. The two corresponding input data
    sets are included.

 6. Special Features: 

 7. Author/Organizer 
    Experiment and Analysis:
    M. Lott, P. Pepin, L. Bourdet, G. Cabaret, J. Capsie, M. Dubor, M. Hot,
    C Goulet;
    CEA (French Atomic Energy Commission), DPA/DEP/SEPP,
    92260 Fontenay aux Roses

    Compilation of data for Sinbad and experiment interpretation using TRIPOLI 4:
    J.C. Nimal
    CEA Centre de Saclay DEN/DM2S/SERMA/LEPP,
    91191 Gif sur Yvette Cedex; France

    Reviewer of compiled data:
    I. Kodeli
    OECD/NEA, 12 bd des Iles, 92130 Issy les Moulineaux, France

 8. Availability: 

 9. References: 
    [1] M. Lott, P. Pepin, L. Bourdet, G. Cabaret, J. Capsie, M. Dubor, M. Hot,
        C. Goulet: Etude expérimentale de l’atténuation des neutrons dans
        différents matériaux de protection à l’aide du dispositif NAÏADE I du
        réacteur ZOE, Note CEA 1386, Dec. 1970
    [2] J. Brisbois, M. Lott, G. Manent:
        Mesure des flux de neutrons thermiques intermédiaires et rapides au moyen
        de détecteurs par activation, Rapport CEA R 2491, August 1964.
    [3] J.P. Both, Y.K. Lee, A. Mazzolo, O. Petit, Y. Peneliau, B. Roesslinger,
        M. Soldevila: TRIPOLI-4 – A Three Dimensional Polykinetic Particle
        Transport Monte Carlo Code, SNA’2003, Paris, September 2003.
    [4] J.P. Both, A. Mazzolo, Y. Peneliau, O. Petit, B. Roesslinger:
        Notice d’utilisation du code TRIPOLI-4.3 : code de transport de particules
        par la methode de Monte Carlo,  rapport CEA-R-6043, 2003.
    [5] J.P. Both, A. Mazzolo, Y. Peneliau, O. Petit, B. Roesslinger:
        User manual for version 4.3 of the TRIPOLI-4 Monte Carlo method particle
        transport computer code, rapport CEA-R-6044, 2003.
    [6] J.C. Nimal: Nouvelles interprétations des expériences NAÏADE 1, 1ere
        Partie : Expériences sur le fer et le graphite, rapport NEA/NSC/DOC(2005)15,
        JT00194885, 25-Nov-2005.
    [7] J.C. Nimal: New interpretation of the NAÏADE 1 experiments, Part 1: the
        Iron and Graphite Experiments, 
        Report NEA/NSC/DOC(2005)15, JT00194842, 24-Nov-2005.
    [8] J.C. Nimal: New interpretation of NAIADE benchmarks,
        Proc. ANS 14th Biennial Topical Meeting of the Radiation Protection and
        Shielding Division, Carlsbad, New Mexico, USA. April 3-6, 2006

 10. Data and Format: 

        Filename    Size[bytes] Content 
    --------------- ----------- ------------- 
 1 naiade-c.htm                           9.234 This information file  
 2 NSCDOC_2005_15 EN.pdf              2.170.594 Description of Experiment, Ref. [7]  
 3 NSCDOC_2005_15 FR.pdf              1.084.441 Description of Experiment, Ref. [6] (in French)  
 4 RPSD2006-JCN.pdf                     578.237 Ref. [8]
 5 naiadegraph_60_fission.data           53.319 TRIPOLI 4 input (direct flux)
 6 bruitdefond_graphite_60_fission.data  54.827 TRIPOLI 4 input (background scattering)

SINBAD Benchmark Generation Date: 12/2006
SINBAD Benchmark Last Update: 12/2006