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Dogleg Duct Streaming Experiment with 14 MeV Neutron Source

 1. Name of Experiment:
    Dogleg Duct Streaming Experiment with 14 MeV Neutron Source (2004)

 2. Purpose and Phenomena Tested:
    The experiment [1] was conducted at the FNS facility at JAERI to study the
    neutrons streaming through doubly bent ducts and estimate the uncertainties
    of calculations for the design of fusion reactors such as ITER, as well as to
    demonstrate the capability of the Monte Carlo transport calculations in the
    design of the fusion reactor shielding. 

 3. Description of the Source and Experimental Configuration:
    Two target rooms are available at FNS. The target that provides a neutron
    yield as large as about 4.0E12 n/s at full beam current was used in the
    experiment. The layout of the room is shown in Fig. 1 The experimental assembly
    was constructed in the wall separating the two target rooms. The assembly
    consists of an iron slab 1700 mm in height, 1400 mm in width, and 1800 mm
    in thickness. A doubly bent duct 300 mm x 300 mm in cross section was shaped
    through the assembly. The geometrical configuration of the dogleg duct
    streaming experiment is shown in Fig. 2. The first horizontal leg of the duct
    was set as high as the D-T neutron source. The second leg was connected
    vertically to the first with a right angle, and the third was horizontally
    to the second. The lengths of the legs were 1150 mm, 600 mm and 650 mm,

 4. Measurement System and Uncertainties:
    Neutron spectra above 2 MeV were measured at several positions by a
    spherical NE213 scintillation spectrometer 40 mm in diameter. The two-gain
    method was adopted in the electronics system to make a wider energy range
    available. Neutron and gamma-ray signals were separated by a pulse shape
    discrimination technique based on the differences in rise time of the
    signal. The pulse height spectrum of recoil protons which represent neutron
    events was unfolded with the FORIST code [2] to obtain the neutron energy
    spectrum. The reactions of 93Nb(n,2n)92mNb, 115In(n,n')115mIn and
    197Au(n,g)198Au were employed as neutron activation dosimeters. The first
    reaction is effective to evaluate the 14 MeV neutron flux, the second is
    sensitive to fast neutrons above 1 MeV, and the third helps to understand
    the amount of the thermal and epithermal neutron flux.

 5. Description of Results and Analysis:
    Reaction rates measured with activation foils in the bent duct and on the
    back surface of the assembly are shown in Table 1 and Fig. 4 under the same
    normalisation as the spectrum. It is observed that the reaction rates of
    93Nb(n,2n)92mNb and 115In(n,n')115mIn caused mainly by fast neutrons
    prominently decrease after the duct bends, while those of 197Au(n,g)198Au
    do not show clear change around the bends.

    Measured neutron spectra are shown in Table 2 and Fig. 3. The D-T neutron
    source intensity was normalised to unity. Positions #3, #5 and #7 are
    located in the duct (see Fig. 2). The spectra become softer with increasing
    path along the duct from the inlet. The spectrum at position #9 is higher
    than at position #7, because the position #9 is located on the extension
    of the first leg and the shield between positions #3 and #9 is only 50 cm.
    It is noteworthy that the 14 MeV peak at position #9 is even larger than
    that at position #7.

    The experiment was analysed by the Monte Carlo codes MCNP-4B and -4C [3]
    using the nuclear data libraries FENDL/2 [4] and JENDL-3.3 [5]. The 
    agreement between the calculated and measured values is generally within
    the Monte Carlo statistical errors, proving that the codes and the nuclear
    data libraries are sufficiently reliable and accurate to estimate streaming
    effects in the shielding design of fusion reactors.

 6. Special Features:

 7. Author/Organizer
    Experiment and analysis:
    Yuichi MORIMOTO, Kentaro OCHIAI, Takashi NISHIO, Masayuki WADA,
    Michinori YAMAUCHI(*) and Takeo NISHITANI(**)
    *Japan Atomic Energy Research Institute, Tokai-mura, Naka-gun, 
    Ibaraki-ken 319-1195, Japan
    E-mails: (*)yamauchi@fnshp.tokai.jaeri.go.jp

    Compiler of data for Sinbad:
    S. Kitsos
    OECD/NEA, 12 bd des Iles, 92130 Issy les Moulineaux, France
    E-mail: stavros.kitsos@free.fr

    Reviewer of compiled data:
    I. Kodeli
    OECD/NEA, 12 bd des Iles, 92130 Issy les Moulineaux, France
    E-mail: ivo.kodeli@oecd.org

 8. Availability:

 9. References:
        T. NISHITANI, "Dogleg Duct Streaming Experiment with 14 MeV
        Neutron Source", J. Nucl. Sci. Technol., supplement 4, 
        p. 42-45 (March 2004).
    [2] M. Matzke and K. Weise, "Neutron spectrum unfolding by the Monte
        Carlo method", Nucl. Inst. Meth., A234, 324 (1985).
    [3] J.F. Briesmeister (Ed.), MCNP - a general Monte Carlo n-particle
        transport code, version 4C, LA-13709-M, Los Alamos National
        Laboratory (2000).
    [4] A. B. Pashchenko, Summary Report of IAEA Consultants' Meeting on
        Selection of Basic Evaluations for the FENDL-2 Library,
        INDC(NDS)-356 (1996).
    [5] K. Shibata, et al., "Japanese Evaluated Nuclear Data Library
        Version 3 Revision-3: JENDL-3.3," J. Nucl. Sci. Technol., 39,
        1125 (2002).
    [6] F. Maekawa, C. Konno, et al., "Investigation of Prediction
        Capability of Nuclear Design Parameters for Gap Configuration in
        ITER through Analysis of the FNS Gap Streaming Experiment",
        J. Nucl. Sci. Technol., Supplement 1, 263 (2000).
    [7] C. Konno, F. Maekawa, et al., "Experimental Investigation on
        Streaming due to a Gap between Blanket Modules in ITER", J. Nucl.
        Sci. Technol., Supplement 1, 540 (2000).
    [8] C. Konno, F. Maekawa, et al., "Overview of Straight Duct Streaming
        Experiments for ITER", Fusion Eng. Des., 51-52, 797 (2000).

10. Data and Format:

         Filename       Size[bytes]  Content
    ------------------ ----------- -------------
    1  fnsstr-a.htm        10.450   This information file
    2  fnsstr-e.htm        13.506   Description of the experiment
    3  fns-str-f1.gif      21.009   Fig. 1: Layout of the target room
    4  fns-str-f2.gif      14.008   Fig. 2: Schematic view of the experimental assembly
    5  fns-str-f3.gif      10.930   Fig. 3: Neutron spectra measured at positions #3, #5, #7 and #9
    6  fns-str-f4.gif       9.300   Fig. 4: Reaction rates measured in the duct and behind the assembly
    7  fns-str-f5.gif       7.233   Fig. 5: Spectra measured and calculated with FENDL/2 at pos. #3
    8  fns-str-f6.gif       7.111   Fig. 6: Spectra measured and calculated with FENDL/2 at pos. #5
    9  fns-str-f7.gif       7.195   Fig. 7: Spectra measured and calculated with FENDL/2 at pos. #7
    10 fns-str-f8.gif       7.259   Fig. 8: Spectra measured and calculated with FENDL/2 at pos. #9
    11 fns-str-f9.gif       6.727   Fig. 9: C/E values of 93Nb(n,2n)92mNb reaction rates in the duct
                                            and behind the assembly
    12 fns-str-f10.gif      6.887   Fig. 10: C/E values of 115In(n,n')115mIn reaction rates in the duct
                                             and behind the assembly
    13 fns-str-f11.gif      8.104   Fig. 11: C/E values of 197Au(n,g)198Au reaction rates in the duct
                                             and behind the assembly
    14 mcnp-F2.inp         25.596   Input data for MCNP4B and 4C calculations (FENDL/2 library)
    15 mcnp-J33.inp        25.751   Input data for MCNP4B and 4C calculations (JENDL-3.3 library)
    16 fns-str-r.xls       32.768   Measured and calculated reaction rates in Microsoft Excel(tm) format
    17 fns-str-s.xls      208.896   Measured and calculated neutron spectra in Microsoft Excel(tm) format 
    18 fns-str.pdf        344.683   Reference [1]

    File fnsstr-e.htm contains the following tables:

      Table 1:    Measured reaction rates
      Table 2:    Measured neutron spectra at positions 3, 5, 7 and 9

    Figures are included in GIF format.