Dogleg Duct Streaming Experiment with 14 MeV Neutron Source
1. Name of Experiment:
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Dogleg Duct Streaming Experiment with 14 MeV Neutron Source (2004)
2. Purpose and Phenomena Tested:
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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:
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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,
respectively.
4. Measurement System and Uncertainties:
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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:
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None
7. Author/Organizer
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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
(**)nisitani@naka.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:
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Unrestricted
9. References:
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[1] Y. MORIMOTO, K. OCHIAI, T. NISHIO, M. WADA, M. YAMAUCHI and
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:
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DETAILED FILE DESCRIPTIONS
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Filename Size[bytes] Content
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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.
