[back to index] [experiment]

SINBAD ABSTRACT NEA-1552/23

KENS p-500 MeV shielding experiment at KEK



 1. Name of Experiment:
    ------------------
    Shielding Experiment using 4m Concrete at KEK Spallation Neutron
    Source Facility (KENS) (2002-2004)


 2. Purpose and Phenomena Tested:
    ----------------------------
    Penetration of up to 500 MeV neutrons, generated on a thick tungsten
    target bombarded by 500 MeV protons, through an ordinary concrete shield
    of 4-m-thickness was studied to check the accuracies of the transmission
    and activation calculation codes.


 3. Description of Source and Experimental Configuration:
    ----------------------------------------------------
    A high-energy neutron source produced in the forward direction from a thick
    tungsten target bombarded by 500 MeV - 5 microA protons was arranged at the
    KENS spallation neutron source facility. Figure 1 shows the vertical and
    horizontal cross sections of the high-energy neutron irradiation room of KENS
    arranged for a shielding experiment. The description of the whole geometry,
    together with the information on the corresponding dimensions, as well as the
    details of the target assembly, shield and the source term simulation, are
    given in file kens-geo.pdf. 
    Using a 0-degree beam course downstream of the target, high-energy neutron
    source produced in the forward direction is available from the beam exit
    (20-cm-width by 15-cm height), which is located 2.5-m away from the center
    of the tungsten target, while a 1.3-m-thick iron beam shutter is open.
    An ordinary concrete shield (see Table 1) of 4-m thickness was assembled in
    contact with the beam exit of the neutron irradiation room, and 7 slots
    reaching the beam axis inside the concrete shield were equipped in every
    40-80 cm thickness for irradiation sample insertion. In a 21-cm wide by 4.5-cm
    thick rectangular slot (slot-1) in the front surface of the shield and in
    6 cylindrical slots of 10.6-cm diameter (slots 2-7) inside the shield,
    shielding plugs filled with the same concrete were inserted during the
    experiment. Acryl capsules containing irradiation samples can be attached at
    the bottom of the plugs, and then placed on the beam axis inside the shield
    from the top of the target station by using a 10-ton crane. The slot-8 is
    located at the end of the 4-m thick shield.
    The angular and energy distributions of neutrons produced from the target
    assembly, calculated using the MARS14 code, is shown in Fig. 2. It can be
    seen that the ratio of the high-energy neutron component in the hundreds of
    MeV region in the 0-degree spectrum is larger than those of other angles.
    The calculated forward neutron spectrum at 0 degree is tabulated in Table 2
    and in the MARS input source routine beg1_src.f. It can be used as a source
    term for the neutron transmission calculation through a 4-m-thick concrete.
    The MARS14 source calculation is described in [2].

 4. Measurement System:
    ------------------
    Activation detectors of bismuth, aluminum, indium and gold foils were
    inserted into 8 slots inside the shield, and attenuations of neutron reaction
    rates were obtained by measurements of gamma-rays from the activation
    detectors. Because of large neutron intensities gradients, a variety of
    detector sizes and thicknesses were employed, as shown in Table 3 and Fig. 3.
    The capsules containing activation detectors were attached to the bottom of
    the shield plugs and were inserted into the 7 slots in the shield from the
    top of the target station. After one week of irradiation, all the detectors
    were removed from every slot and the spectra of gamma-rays from radioactive
    nuclides produced at activation detectors were measured by Ge detectors. The
    half lives, gamma-ray energies and their emission ratios for radioactive
    products, which were analyzed in this work, are tabulated in Table 4. The
    efficiencies of the Ge-detector, which include the self-absorption effect,
    were calculated with the EGS4 code for every detector type and size. From
    analyses of the photo peak counts of each gamma-ray, the following activation
    reaction rates were obtained:

    Reaction            Threshold[MeV]
    209Bi(n,9n)201Bi    61.73 
    209Bi(n,8n)202Bi    53.98 
    209Bi(n,7n)203Bi    45.31 
    209Bi(n,6n)204Bi    37.99 
    209Bi(n,5n)205Bi    29.63 
    209Bi(n,4n)206Bi    22.56 
    27Al(n,alpha)24Na    3.25 
    27Al(n,X)22Na       ~30 
    27Al(n,X)7Be        ~100 
    115In(n,ní)115mIn   ~0.5 
    198Au(n,gamma)197Au Thermal

    The reaction rates were estimated using one or a few gamma-rays from the
    radioactive products, and the reaction rates in the same slot agreed within
    about 10%, independently of gamma-rays analyzed or detector sizes used.

    For the cross section data for activation reactions See graph.


 5. Description of Results and Analysis:
    -----------------------------------
    The numerical data of the neutron dose are given in Table 5.

    Experiment Analysis:
    The experiment was simulated by the authors using the Monte-Carlo MARS14 code.
    The MARS14 input data used in this analysis include besides the main input
    (mars.inp) also 2 subroutines:
    beg1_src.f: source routine
    reg1.f: geometry routine

    The transport calculations are presented in Refs. [1] and [2]. The comparisons
    between the calculated and measured reaction rates of 209Bi(n,xn)210-xBi (x=4-8),
    27Al(n,alpha)24Na, 115In(n,ní)115mIn and 198Au(n,gamma)197Au for all slots
    inside the shield is shown in Figure 5. Except some underestimations for the
    209Bi(n,8n)202Bi reaction, which has a threshold of 54 MeV, the calculations
    generally gave good agreements with the experiment within a factor of 3.
    In the latest analysis shown in Figure 5 the self-shielded response function
    for Au-197(n,gamma) was used, which improved the C/E agreement with respect
    to the one given in Refs. [1] and [2].
     

 6. Special Features:
    ----------------
    None


 7. Author/Organizer:
    ----------------
    Experiment and analysis:
    Noriaki Nakao
  (Former Institution)
    High energy Accelerator Research Organization (KEK)
    Oho 1-1, Tsukuba, Ibaraki 306-0801, Japan
  (Present address)
    Accelerator Physics / Accelerator Division,
    Fermi National Accelerator Laboratory,
    MS220, P.O.Box 500,  Batavia, IL 60510-0500, USA
    Phone:1-630-840-3315    Fax:1-630-840-6039

    Compiler of data for Sinbad:
    I. Kodeli
    OECD/NEA, 12 bd des Iles, 92130 Issy les Moulineaux, France

    Reviewer of compiled data:
    Noriaki Nakao
    Accelerator Physics / Accelerator Division,
    Fermi National Accelerator Laboratory,
    MS220, P.O.Box 500,  Batavia, IL 60510-0500, USA
    Phone:1-630-840-3315    Fax:1-630-840-6039


 8. Availability:
    ------------
    Unrestricted


 9. References:
    ----------
    [1] [PPT Presentation] N. Nakao, H. Yashima, M. Kawai, K. Oishi, H. Nakashima,
        K. Masumoto, H. Matsumura, S. Sasaki, M. Numajiri, T. Sanami, Q. Wang,
        A. Toyoda, K. Takahashi, K. Iijima, K. Eda, S. Ban, H. Hirayama, S. Muto,
        T. Nunomiya, S. Yonai, D. R. H. Rasolonjatovo, K. Terunuma, K. Yamauchi,
        P. K. Sarkar, E. Kim, T. Nakamura and A. Maruhashi, "Arrangement of
        high-energy neutron irradiation field and shielding experiment using 4 m
        concrete at KENS", Proc. 10th Int. Conf. on Radation Shielding  (ICRS10),
        Madeira, Portugal, May 9-14, 2004; Radiat. Prot. Dosim. Vol.116, No.1-4,
        pp553-557 (2005).

    [2] N. Nakao, H. Yashima, M. Kawai, K. Oishi, H. Nakashima, S. Sasaki, K. Masumoto,
        M. Numajiri, T. Sanami, H. Matsumura, Q. Wang, A. Toyoda, K. Iijima,
        K. Takahashi, S. Ban, H. Hirayama, S. Muto, T. Nunomiya, S. Yonai,
        D.R.H. Rasolonjatovo, K. Terunuma, T. Nakamura, E. Kim, P. K. Sarkar
        and A. Maruhashi, "KENS Shielding Experiment (1) - Measurement of Neutron
        Attenuation through 4m Concrete Shield Using a High Energy Neutron
        Irradiation Room", Proc. 2nd iTRS Int. Symposium on Radiation Safety
        and Detection Technology (ISORD-2), Tohoku University, Sendai, JAPAN,
        July 24-25, (2003); J. Nucl. Sci. Technol. Suppl.4, p.22 (2004)

        Radioactive Spallation Products by High Energy Neutrons:
    [3] [Web paper] H. Matsumura, K. Masumoto, N. Nakao, Q. Wang, A. Toyoda, M.
        Kawai, T. Aze and M. Fujimura, "Characteristics of high-energy neutrons
        estimated using the radioactive spallation products of Au at the 500-MeV
        neutron irradiation facility of KENS", Proc. 10th Int. Conf. on Radation
        Shielding (ICRS10), Madeira, Portugal,May 9-14, 2004 ; Radiat. Prot.
        Dosim. Vol.116, No.1-4, pp1-5 (2005). 

        Activation products inside concrete:
    [4] [Web paper] K. Oishi, N. Nakao, K. Kosako, H. Yamakawa, H. Nakashima,
        M. Kawai, H. Yashima, T. Sanami, M. Numajiri, T. Shibata, H. Hirayama, T.
        Nakamura, "Measurement and analysis of induced activities in concrete
        irradiated using high-energy neutrons at KENS neutron spallation source
        facility", Proc. 10th Int. Conf. on Radation Shielding (ICRS10), Madeira,
        Portugal,May 9-14, 2004 ; Radiat. Prot. Dosim., Vol.115 No.1-4, pp623-629
        (2005). 

        Target Fragmentation by High Energy Neutron:
    [5] H. Matsumura, T. Sanami, K. Masumoto, N. Nakao, A. Toyoda, M. Kawai,
        T. Aze, H. Nagai, M. Takada and H. Matsuzaki, "Target dependence of
        beryllium fragment production in nuetron- and alpha-induced nuclear
        reactions at intermediate energies", Radiochim. Acta 93 (2005) pp497-501. 

        Shielding Experiment with Activation Detector and Imaging Plate:
    [6] Q. Wang, K. Masumoto, A. Toyoda, N. Nakao, M. Kawai and T. Shibata, "KENS
        Shielding Experiment (2) - Measurement of the Neutron Spatial Distribution
        inside and outside of a Concrete Shield using an Activation Foil and an
        Imaging Plate Technique", Proc. The 2ns iTRS International Symposium on
        Radiation Safety and Detection Technology (ISORD-2), Tohoku University,
        Sendai, JAPAN, July 24-25, (2003); J. Nucl. Sci. Technol. Suppl.4, p.26
       (2004) 

        Shielding Experiment 2003 Detail Report (Japanese):
    [7] H. Yashima and N. Nakao, "Deta Analysis for Neutron Reaction Rates of
        Activation Detectors in KENS Shielding Experiment - Experiment on January
        2003-", KEK Internal 2003-10 (Feb. 2004).


10. Data and Format:
    ---------------

    DETAILED FILE DESCRIPTIONS
    --------------------------
     Filename             Size[bytes]   Content
    --------------------- ----------- -------------
  1 kenssh-a.htm               15,450 This information file
  2 kenssh-e.htm                9,915 Tables with numerical data
  3 mars.inp                      404 Input data for MARS14 code
  4 beg1_src.f                  5,726 Source routine for the MARS calculation
  5 reg1.f                      7,256 Geometry routine for the MARS calculation
  6 KENS-geo.jpg              216,539 Fig. 1: Experimental Geometry [jpg] 
  7 KENS-geo.pdf              174,192 Fig. 1: Experimental Geometry (target, shield
                                              and source term simulation) [PDF] 
  8 KENS-source.xy.xls         26,624 Tab. 2: Neutron source distributions (in XLS format)
  9 KENS-source.jpg           146,960 Fig. 2: MARS14 neutron source spectra for
                                              different directions
 10 kens-foil.jpg              75,815 Tab. 3: Activation detector arrangement inside concrete
 11 KENSdetectors.jpg         431,610 Fig. 3: Detectors used in the experiment
 12 act-xs.jpg                155,433 Fig. 4: Activation cross section data
 13 KENS-exp.xls               12,800 Tab. 5: Measured reaction rates (in XLS format)
 14 KENS-results.jpg          171,230 Fig. 5: Comparison calculation-measurement 
 15 rpd116-KENS-Nakao.pdf     315,953 Ref. [1]
 16 PPT-KENS-ICRS10.pdf     1,319,402 Ref. [1] - ppt presentation
 17 Proc-ISORD2-nakao.pdf     490,065 Ref. [2]


    File kenssh-e.htm contains the following table:

      Table 1: Composition and Density of Concrete.
      Table 2: Neutron source distributions.
      Table 3: Activation detector arrangement inside the concrete shield.
      Table 4: Activation reactions and physical properties of gamma-rays.
      Table 5: Measured reaction rate distributions.

   Figures are included in the JPG and PDF formats.

SINBAD Benchmark Generation Date: 08/2006
SINBAD Benchmark Last Update: 08/2006