1. Name of Experiment:
 ------------------
 Leakage Neutron and Gamma Spectra from 40 and 60 cm diameter Silicon
 Sphere Pile With 14 MeV Neutrons (March 1987)

2. Purpose and Phenomena Tested:
 ----------------------------
 The leakage current spectrum from the outer surface of the sphere pile
 with 14 MeV neutrons normalized per source neutron was measured [1], [2],
 [3], [4]. The gamma-rays were produced from (n,xg) reactions.

3. Description of Source and Experimental Configuration:
 ----------------------------------------------------
 The pulsed beam line of the intense 14 MeV neutron source facility
 OKTAVIAN [5] at Osaka University was used. Neutrons were produced
 by bombarding a 370 GBq tritium target with 250 keV deuteron beam.
 The energy spectrum of the neutron source was measured using the same
 detection system as for the leakage spectrum measurement. The spatial
 distribution of the emitted neutrons was measured for the target
 assembly, but for the purpose of the analysis an isotropic neutron
 source distribution is assumed. The neutron source spectrum is
 given in Table 1. The other information about the neutrons emission
 is given elsewhere [6].

 The neutron spectra were measured with the time-of-flight (TOF)
 technique. A tritium neutron producing target was placed at the
 center of the pile. A cylindrical liquid organic scintillator NE-218
 was used as a neutron detector, which was located about 11 m from the
 tritium target and at 55 deg. with respect to the deuteron beam axis.
 A pre-collimator made of polyethylene-iron multi-layers was set between
 the pile and the detector in order to reduce the background neutrons.
 The aperture size of this collimator was determined so that the whole
 surface of the pile facing the detector could be viewed. The details of
 the experimental set-up are shown in Figure 1.

 Gamma-rays were detected with a cylindrical NaI crystal and the
 energy spectra were obtained from the unfolding process of the
 gamma-ray pulse-height spectra, using a response matrix of the
 NaI detector. The detector was located at 5.8 m distance from the
 neutron source and counted the gamma-rays emitted from the sphere.
 The energy spectrum of gamma-rays at the source is shown in Table 2,
 and Figures 4 and 5. Time spectra of neutrons and gamma-rays from the
 sphere were measured simultaneously with the pulse-height spectra by
 means of a TOF technique.

 The pile was made by filling a spherical vessels with grannular silicon.
 The stainless steel (JIS SUS-304) vessel with 61.0 cm outer diameter
 was equipped with a 20 cm inner diameter void at its center and a
 11 cm diameter reentrant hole for the target beam duct. The external
 and the internal vessel thickness was 0.5 cm and 0.2 cm respectively.
 The details of the pile geometry are given in Figure 2. The gamma-ray
 leakage spectrum has been also measured for a 40.0 cm diameter pile
 shown in Figure 3.

 Granular silicon was at least 99.9% pure, with density of 1.29 g/cm3.

 The assumed composition of stainless steel is 18.5 % Chromium,
 70.4 % Iron and 11.1 % Nickel, with density of 7.86 g/cm3.

4. Measurement System:
 ------------------
 A cylindrical liquid organic scintillator NE-218 (12.7 cm-diam,
 5.1 cm-long) was used as a neutron detector. The detector efficiency
 was determined by combining:
 1) the Monte Carlo calculation,
 2) the measured efficiency derived from the TOF measurement of Cf-252
 spontaneous fission spectrum and the Watt's spectrum, and
 3) the measured efficiency from the leakage spectrum from a graphite
 sphere, 30 cm in diameter with the similar detection system.

 To monitor the absolute neutron spectrum per source neutron, a
 cylindrical niobium foil was set in front of the tritium target and
 irradiated during the TOF experiment. From the gamma-ray intensity
 of the induced activity, Nb-92m and the integrated counts of the
 source neutron spectrum, the absolute neutron leakage spectrum can
 be obtained. The formulation of this procedure is described in the
 Oktavian Report [7].

 To measure the gamma spectra, OKTAVIAN was run in the pulsed mode
 with a repetition frequency of 500 kHz. The pulse width was 3 ns in
 FWHM and the difference in flight times between the 14 MeV neutrons
 and the prompt gamma-rays was about 90 ns from the sphere to the
 detector. Since those were enough to separate the gamma-rays from
 the neutron background in the TOF spectra, the desired gamma-rays
 could be discriminated from a neutron background.

 The gamma emission spectra were dominated by the gamma-rays from
 (n,n') and (n,2n) reactions rather than the gamma-rays from
 (n,xg) reaction. The data are therefore available to the assessment
 in the nuclear data for energy distributions of gamma-rays from
 non-elastic scattering by high energy neutrons.


5. Description of Results and Analysis:
 -----------------------------------
 The measured neutron leakage spectrum from a 60 cm diameter silicon
 pile is given in Table 3 and in Figure 6. Numerical data for the
 gamma-ray leakage spectra, measured from a 40 cm and a 60 cm diameter
 silicon piles are given in Tables 4 and 5 and in Figures 7 and 8
 respectively.
 In ref. [9] the neutron leakage spectra measurements from a 40 cm Si
 file are mentioned. Only plots are available in Figure 9, and the energy
 integrated data are given at 4 energy groups in Table 6.

 Error Assessment:

 The experimental errors in the measured neutron spectra include only
 statistical deviation (1 s). The relative error to measure the niobium
 activation foils is less than 1 % (0.4 to 1 %), which is not included.

 In the measured gamma spectra the following sources were included
 in the errors:
 (a) Uncertainty in monitoring absolute fluxes of the source neutrons,
 (b) Errors of the response matrix,
 (c) Statistical deviation (1 s).


 Example of Experiment Analysis:

 The sample inputs for the MCNP-4B code are given in files mcnp60_n.inp
 and mcnp60_g.inp.

 Benchmark calculations with the MCNP code described in ref. [8] were
 performed with FSXLIB-J3 and BMCCS library, and adopted ENDF/B-III for
 silicon. Measured and calculated spectra are shown in Figures 6, 7 and 8.

 More recent benchmark calculation has been performed in ref. [9] by
 MCNP-4A code with JENDL-3.2, JENDL-FF, FENDL-1 and FENDL-2 (ENDF-VI)
 libraries. Calculated and measured spectra for the 40 cm diameter
 silicon pile are shown in Figure 9, and for the 60 cm diameter silicon
 pile in Figures 10, 12 and 13. Recent results by A. Trkov using the
 MCNP-4B code and the EFF-3/ENDF/B-VI evaluations are given in Figure 11.
 Neutron spectra calculated by FENDL-1 (=BROND2) are larger than the
 experimental data. Calculated spectra with ENDF/B-VI and EFF-3 show
 good agreement with the experimental data. Gamma-ray spectrum
 calculated by FENDL-1 gives smaller than the measured spectrum, while
 both JENDL-FF and ENDF/B-VI predict adequately the measured spectrum.

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


7. Author/Organizer:
 ----------------
 Chihiro Ichihara, Katsuhei Kobayashi:
 Research Reactor Institute, Kyoto University
 Noda, Sennan-gun, Osaka 590-04, Japan

 Shu A. Hayashi:
 Institute for Atomic Energy, Rikkyo University
 2-5-1 Nagasaka, Yokosukas Kanagawa 240-01, Japan

 Itsuro Kimura:
 Department of Nuclear engineering, Faculty of Engineering,
 Kyoto University
 Yoshida-honmachi, Sakyo-ku, Kyoto 606, Japan

 Junji Yamamoto, Akito Takahashi, T. Kanaoka, I. Murata, K. Sumita:
 Department of Nuclear Engineering, Faculty of Engineering,
 Osaka University
 2-1, Yamada-oka, Suita, Osaka 565, Japan

 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:
 A. Trkov
 IAEA/Nuclear Data Section
 Wagramerstrasse 5, P.O.Box 100, A-1400 Vienna, Austria
 E-mail : A.Trkov@iaea.org

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


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


9. References:
 ----------

 [1] Ichihara C., et al.: Proc. Int. Conf. on Nucl. Data for Sci.
 and Technol., Mito, Japan, pp.319-322 (1988).
 [2] Ichihara C., et al.: Proc. Second Specialists' Meeting on Nucl.
 Data for Fusion Reactors (1991), JAERI-M 91-062 (1991).
 [3] Yamamoto J. et al.: "Gamma-Ray Emission Spectra from Spheres with
 14 MeV Neutron Source", JAERI-M 89-026, 232 (1989).
 [4] Yamamoto J. et al.: "Integral Experiment on Gamma-Ray Production
 at OKTAVIAN", JAERI-M 91-062, 118 (1991).
 [5] Sumita K., et al.: Proc. 12th SOFT, Vol. 1 (1982)
 [6] Yamamoto J. et al.: "Numerical Tables and Graphs of Leakage Neutron
 Spectra from Slabs of Typical Shielding Material with D-T Neutron
 Source", OKTAVIAN-Report A-8305, Dept. of Nuclear Eng.,
 Osaka University (1983).
 [7] Takahashi A., et el.: OKTAVIAN Report, C-83-02 (1983).
 [8] Sub Working Group of Fusion Reactor Physics Subcommittee:
 Collection of Experimental Data for Fusion Neutronics Benchmark,
 JAERI-M-94-014, Feb. 1994.
 [9] Fujio Maekawa, Masayuki Wada, Chihiro Ichihara, Yo Makita,
 Akito Takahashi, Yukio Oyama:
 Compilation of Benchmark Results for Fusion Related Nuclear Data,
 JAERI-Data/Code 98-024, Nov. 1998.


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

 DETAILED FILE DESCRIPTIONS
 --------------------------
 Filename Size[bytes] Content
 ---------------- ----------- -------------
 1 oksi-abs.htm 14.722 This information file
 2 oksi-exp.htm 19.247 Description of experiment
 3 oksi-f1.gif 13.827 Figure 1: Experimental arrangement of the OKTAVIAN Facility
 4 oksi-f2.gif 9.887 Figure 2: 60 cm diameter vessel (Type-III)
 5 oksi-f3.gif 7.345 Figure 3: 40 cm diameter vessel (Type-II)
 6 oksi-f4.gif 10.398 Figure 4: Gamma-ray emission spectrum from the neutron
   source
 6 oksi-f5.jpg 41.826 Figure 5: Gamma-ray source spectrum from MCNP input and 
   Table 2
 7 oksi-f6.gif 12.094 Figure 6: Neutron spectra from Si 60 cm pile, ref. [8]
 8 oksi-f7.gif 9.797 Figure 7: Gamma-ray spectra from Si 40 cm pile, ref. [8]
 9 oksi-f8.gif 10.441 Figure 8: Gamma-ray spectra from Si 60 cm pile, ref. [8]
10 oksi-f9.gif 25.898 Figure 9: Neutron spectra from Si 40 cm pile - ENDF/B-VI, 
   ref. [9]
11 oksi-f10.gif 13.918 Figure 10: Neutron spectra from Si 60 cm pile, ref. [9]
11 oksi-f11.jpg 66.385 Figure 11: Neutron spectra from Si 60 cm pile - EFF-3, 
   ENDF/B-VI (by A. Trkov)
12 oksi-f12.gif 18.042 Figure 12: Gamma-ray spectra from a Si 60 cm pile, ref. [9]
13 oksi-f13.gif 17.599 Figure 13: Gamma-ray spectra from a Si 60 cm pile - 
   ENDF/B-VI, ref. [9]
14 mcnp60_n.inp 7.715 Input for MCNP4B neutron calculations - Si 60 cm pile
   (by F. Maekawa, modifications A. Trkov)
15 mcnp60_g.inp 1.878 Input for MCNP4B gamma calculations - Si 60 cm pile 
   (by F. Maekawa)
16 j94-014.pdf 34.067.821 Reference
17 j98-024.pdf 12.837.046 Reference

 File oksi-exp.htm contains the following tables:

 Table 1: Neutron source spectrum for silicon
 Table 2: Gamma-ray energy spectrum at the source
 Table 3: Measured neutron leakage spectrum from a Si sphere of 60 cm diameter
 Table 4: Measured gamma-ray leakage spectrum from a Si sphere of 40 cm diameter
 Table 5: Measured gamma-ray leakage spectrum from a Si sphere of 60 cm diameter
 Table 6: Integrated neutron flux from Si spheres of 40 and 60 cm diameter

 Figures are included in GIF and JPG formats.

SINBAD Benchmark Generation Date: 02/2002
SINBAD Benchmark Last Update: 02/2002