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 1. Name of Experiment:
    FNG-ITER Dose Rate Experiment

 2. Purpose and Phenomena Tested:
    The purpose is to validate dose rate calculations for the International
    Thermonuclear Experimental Reactor (ITER). The experiment [1-4] was performed
    at the 14 MeV Frascati Neutron Generator (FNG) on a stainless steel/water
    assembly, in which a neutron spectrum was generated similar to that occurring
    in the ITER vacuum vessel. The mock-up was irradiated at FNG for sufficiently
    long time to create a level of activation which was, after shut down,
    followed by dosemeters for a cooling time assumed to be required for allowing
    personal access. 

 3. Description of Source and Experimental Configuration:
    The 14-MeV d-T Frascati Neutron Generator (FNG, [5]) was the neutron
    source. The angular dependence of the source intensity is presented in
    Figure 1. The angular dependence of the source energy  distribution is
    shown in Figure 2.
    The x-y view of the geometry of the mock-up is outlined in Figure 3. It
    consists of a combination of slabs made from the water equivalent material
    Perspex and the stainless steel SS316 (simulating shield-blanket and vacuum
    vessel) and has a front cross-section area of 100 cm x 100 cm. The total
    thickness of the assembly is 71.83 cm. 
    A cavity was arranged within the block, 119.8 mm (z) x 150 mm (x) x 126.0 mm
    (in the beam direction, y axis), behind a 22.37-cm-thick shield. A void
    channel (27.4 mm inner diameter) was included in front of the cavity to
    study the effect of streaming paths in the bulk shield (Fig.3). The channel
    wall was made of stainless steel AISI316 with 1.3 mm thickness.
    A parallelepiped box was used to locate detectors inside the cavity, with
    2-mm-thick bottom and lateral walls (stainless steel AISI316). 

 4. Measurement System:
    The following quantities are measured :

        a - Shut down dose rate in the cavity centre (continous measurement
            by an active dosemeter)
        b - Dose rate in the cavity centre, integrated measurement by
            thermo-luminescent detectors (TLD-300, GR-200A)
        c - Ni-58(n,p)Co-58 and Ni-58(n,2n)Ni-57 activation reaction rates
            during irradiation, using Ni foils

    The continuous measurement of the dose rate was taken in the cavity centre
    after shut down from half an hour to more than three months of cooling time,
    using a  Geiger-Muller detector (G-M, Mod. 7312 - Vacutec) with a
    Multi-Channel Scaler with variable dwell time (EG&G Ortec). The detector
    (12 mm in diameter, 80 mm in length) was located in the cavity centre in
    front of the open channel (Fig.3). The total experimental uncertainty was
    ± 10% for G-M detector.
    High sensitivity thermoluminescent detectors of the type TLD-300 (CaF2:Tm)
    [6], GR-200A (LiF:Mn, Cu, P) were also used to measure independently the dose
    rate in the cavity centre (close to G-M) at four decay times (8.2, 12.4,
    19.2 and 33.2 days, for time intervals ranging from 18 to 22.5 hours). The
    total error associated with the measurements was ±17%. The dose rates
    measured with TLD in the cavity centre was in agreement within 12% with
    values obtained with the Geiger-Muller detector, within the combined
    experimental uncertainties.

    Activation measurement were carried out using Ni foils located on the
    cavity walls (Figure 4). The goal was to measure the reaction rate of
    Ni-58(n,p) producing the Co-58  (responsible of most of the dose rate in
    the relevant decay time), and the reaction rate of Ni-58(n,2n)  which
    produces the Ni-57 (the second most important contributor to total dose
    rate in the first week after shutdown, after Mn-56 is decayed). The total
    experimental error was ±5%. 

    In May 8-10, 2000 the mock-up was irradiated by 14-MeV neutrons at FNG, for
    a total of 18 hours in three days (Table 5 and Figure 5).
    The total neutron production was 1.815E+15.

 5. Description of Results and Analysis:
    The experiment analysis was performed using a rigorous two-step method (R2S)
    employing the MCNP-4C [7] code with FENDL/MC-2.0 [8] cross sections for
    calculating neutron transport (in a first run) and decay gamma transport (in 
    a second run) in sequential order, and the FISPACT [9] inventory code with
    FENDL/A-2.0 [10] activation cross sections for calculating the decay gamma
    source distribution as a function of irradiation history and cooling time.

    Two different MCNP models of the FNG assembly were employed: one for the
    neutron transport calculation during irradiation (mcnp_n.inp, “irradiation
    model”) and the other one for the decay gamma transport calculation after
    irradiation (mcnp_g.inp, “shut-down model”). In this way  proper account is
    taken of the fact that during the irradiation the central cavity was empty
    and the lateral access was plugged whereas after irradiation the plug was
    removed and the detectors were inserted into the cavity. 

    The neutron flux spectra are calculated in the VITAMIN-J 175 group structure
    for all non-void cells of the “FNG irradiation model” and are routed to FISPACT.
    Activation inventories and decay gamma sources (spectrum and intensity) are then
    calculated for all material cells making use of the associated neutron flux
    spectra. This requires one FISPACT-calculation per cell and material taking
    into account the proper irradiation history. 

    The resulting decay gamma source distribution is then routed back to MCNP. 
    The MCNP decay gamma transport calculation is performed with the “FNG shut-down
    model” (mcnp_g.inp) making proper use of the decay gamma sources as provided
    by the preceding FISPACT calculations for all non-void geometry cells. The
    dose rate in air is calculated in a cell in the cavity centre (cell#651
    simulating the GM detector) using tally f6 of MCNP.

    The description of the irradiation history is given in the FISPACT input
    fisp_620.inp (relative to one cell, e.g. cell#620 of mcnp_n.inp).
    A pre-analysis was carried out in order to investigate the origin of the
    doserate: Figure 6 shows the contributions of major nuclides to the total
    contact dose rate, as calculated by FISPACT at the inner cavity wall. Mn-56
    dominates at short times (i.e. t<1 d), Ni-57 at around 1 d, and then Co-58
    dominates in the time range of practical interest for allowing personal access
    for maintenance purposes. The nuclei  considered in the figure contribute to
    more than 95% of the total dose rate, as shown in the same figure by the
    black line.
    The Ni-58(n,p)Co-58 or Ni-58(n,2n)Ni-57 reaction rates were calculated
    in two ways: 

    1. using a procedure similar to R2S method, i.e. using FISPACT with
       Ni-58(n,p) and (n,2n) cross sections from FENDL/A-2. Statistical errors
       on MCNP flux calculations are ±2.5%.  
    2. calculating the reaction rate is directly in the MCNP run taking the
       Ni-58(n,p) and (n,2n) cross sections from the dosimetry file IRDF-90.2
       [11] and from FENDL/MC-2. Statistical errors on  reaction rate
       calculations are ±2.5%.

    The measured dose rate are given in Table 6 (G-M) and 7 (TLD), and Figure 7.
    The calculated ones are given in Table 10 at cooling times equal to 1, 7,
    15, 30, 60 days.
    The measured Ni-58(n,p)Co-58 and Ni-58(n,2n) reaction rates are given in
    Tables 8 and 9 respectively. The calculated reaction rates are given in
    Tables 11-12.

 6. Special Features:

 7. Author/Organizer:
    Experiment and analysis:

    P. Batistoni, M. Angelone, M. Pillon, L. Petrizzi 
    Centro Ricerche Energie Frascati
    UTS Fusione  
    Via E. Fermi 27
    C.P. 65
    I-00044 Frascati (Rome) 

    Compiler of data for Sinbad:
    P. Batistoni
    Centro Ricerche Energie Frascati
    UTS Fusione  
    Via E. Fermi 27
    C.P. 65
    I-00044 Frascati (Rome) 
    E-mail: batiston at efr406.frascati.enea.it

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

    The experiment and the corresponding analysis was performed in the framework of
    the EFDA (European Fusion Development Agreement) ITER Task (T-426-1998/2000).

 8. Availability:

 9. References:

    [1] P. Batistoni, M. Angelone, L. Petrizzi, M. Pillon, H. Freiesleben,
        D. Richter, K. Seidel, S. Unholzer, Y. Chen, U. Fischer, Experimental
        Validation of Shut-Down Dose Rates, Final Report, June 2001
    [2] P. Batistoni, M. Angelone, L. Petrizzi, M. Pillon, “Benchmark
        Experiment for the validation of shut down activation and dose
        calculation in a fusion device”, Journal of Nuclear Science and
        Technology, Sup. 2, p. 974-977 (August 2001), ND2001.
    [3] P. Batistoni, L. Petrizzi, Task T426 - Neutronics Experiments,
        Experimental Validation of Shut Down Dose Rates, EFF-Doc-726, March 2000
    [4] P. Batistoni, S. Rollet, Y. Chen, U. Fischer, L. Petrizzi, Y.
        Morimoto, “Analysis of dose rate experiment : comparison between
        FENDL, EFF/EAF and JENDL nuclear data libraries”, SOFT 2002
    [5] M. Martone, M. Angelone, M. Pillon, The 14 MeV Frascati Neutron 
        Generator, Journal of Nuclear Materials 212-215 (1994) 1661-1664;
    [6] M. Angelone, P. Batistoni, M. Pillon, and V. Rado:
        Gamma and Neutron Dosimetry using CaF2:Tm Thermoluminescent
        Dosimeters for Fusion Reactor Shielding Experiments (EFF-Doc-614 (1997))
    [7] Briesmeister, J. F. (Ed.), MCNP - A general Monte Carlo n-particle
        transport code, version 4C, Report LA12625, Los Alamos, September
    [8] S. Ganesan and P. K. McLaughlin, FENDL/E - evaluated nuclear data
        library of neutron interaction cross-sections and photon production
        cross-sections and photon-atom interaction cross-sections for fusion
        applications, version 1.0, Report IAEA-NDS-128, Vienna, May 1994.
    [9] R. A. Forrest, J-Ch. Sublet, “FISPACT-99: User manual”, Report UKAEA
        FUS 407, December 1998
   [10] M. Herman, A. B. Pashchenko, Extension and improvement of the FENDL
        library for fusion applications (FENDL-2), Report INDC(NDS)-373, IAEA  
        Vienna, 1997.
   [11] N. P. Kocherov, P. K. McLaughlin, The International Reactor Dosimetry
        File (IRDF-90), Report IAEA-NDS-141, Rev. 2, Oct. 1993.

10. Data and Format:

  FILE     NAME        bytes   Content
  ---- ------------    ------   -------
   1   fngdos-a.htm    16,272  This information file 
   2   fngdos-e.htm    75,464  Description of Experiment 
   3   mcnp_n.inp      49,281  3-D model for MCNP-4C calculations of neutron
                               flux (irradiation model)
   4   mcnp_g.inp      67,976  3-D model for MCNP-4C calculations of dose rate 
                               (decay gamma transport, shut down model)
   5   fisp_620.inp     1,014  Input for FISPACT run (e.g. for cell 620)
   6   fisp_620.flx     1,827  Neutron flux, calculated in mcnp_n.inp, for
                               FISPACT run (e.g. for cell 620)
   7   fisp_620.out   843,563  Output of FISPACT run (e.g. for cell 620)
                               containing decay g-ray spectra to be input in
   8   source.for      45,178  FORTRAN subroutine for MCNP source description
   9   fig1.gif         5,242  Fig. 1: Angular dependence of the source 
  10   fig2.gif         9.505  Fig. 2: Energy/angular dependence of the source 
  11   fig3.gif        16,922  Fig. 3: Geometry of the experimental mock-up 
  12   fig4.gif        10,592  Fig. 4: Nickel activation foil positions in the
  13   fig5.gif        20,177  Fig. 5: Neutron irradiaton time profile
  14   fig6.gif        15,487  Fig. 6: Percent contributions of most important
                               radioisotopes to the total contact dose rate,
                               calculated by FISPACT for cell 620 of mcnp_n.inp.
  15   fig7.gif        13,405  Fig. 7: Measured dose rate in the cavity centre
                               as a function of cooling time.
  16   fig8.gif         9,633  Fig. 8: Geometry of the TiT target
  17   fng-dose.pdf 2,110,390  Ref. 1
  18   nd2001.pdf     330,452  Ref. 2
  19   eff-726.pdf    161,239  Ref. 3
  20   eff-614.pdf    585,759  Ref. 6

    File fngdos-e.htm contains the following tables:

Tab. 1: Angular dependence of the source
Tab. 2: Angular/energy dependence of the source energy distribution 
Tab. 3: Geometrical arrangement of the bulk shielding assembly
Tab. 4: Chemical composition of stainless steel SS316
Tab. 5: Irradiation history
Tab. 6: Measured (E) dose rates inside the cavity (G-M)
Tab. 7: Measured (E) dose rates in the cavity (TLD)
Tab. 8: Measured (E) Ni-58(n,p)Co-58 reaction rates
Tab. 9: Measured (E) Ni-58(n,2n)Co-58 reaction rates       
Tab.10: Calculated dose rate (C) - Comparison between calculated
        and measured values (C/E ratios) 
Tab.11: Comparison between calculated and measured Ni-58(n,p)
        reaction rates (C/E ratios).
Tab.12: Comparison between calculated and measured Ni-58(n,2n)
        reaction rates (C/E ratios).

    The figures are given in gif format.

SINBAD Benchmark Generation Date: 4/2003
SINBAD Benchmark Last Update: 4/2003