SINBAD ABSTRACT NEA-1553/76
IPPE neutron transmission through vanadium shells
1. Name of Experiment:
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IPPE neutron transmission benchmark experiment with 14 MeV neutrons through
vanadium shells.
2. Purpose and Phenomena Tested
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Neutron leakage spectra between 50 keV and 15 MeV from two vanadium shells
were measured by the time-of-flight technique using a 14 MeV neutron
generator. The spheres had radius of 5 and 12 cm and wall thicknesses of
3.5 and 10.5 cm.
The experiments were performed in two phases in 1996 and 1997.
3. Description of Source and Experimental Configuration
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A Cockroft-Walton type accelerator, the KG-0.3 pulse neutron generator in
Obninsk, was used to accelerate deuterons to a maximum kinetic energy of
310 keV. The layout of the experiment is shown in Figure 1.
The deuterons were led through a conical aluminum tube of only 0.5 mm wall
thickness and collimated by a diaphragm with an 8 mm hole to a solid
Titanium-Tritium target based on a copper radiator 0.8 mm thick and with
diameter 11 mm. Beam spot diameter was 5 mm.
The center of the target is located in the geometrical center of the vanadium
shell. For monitoring the neutron source strength, the alpha particles
generated in the deuterium-tritium reaction were detected at 175 deg. through
a 1 mm diameter collimator by a silicon surface barrier (SSB) detector.
The ion pulse width is 2.5 ns. The repetition period of the pulse can be set
arbitrarily to multiples of 200 ns. The mean beam current for 800 ns. period
is 1 microampere.
The mean energy and yield of the '14 MeV' neutron source peak are slightly
angle dependent, as shown in Figure 3.
Two spherical shells of high purity vanadium were available for the experiment.
They are shown in Figure 2. Their dimensions and masses are given in Table 1.
The density of every sphere was measured and found to agree with the
literature value of 6.09 g/cm3. The material composition is given in Table 2.
4. Measurement System and Uncertainties:
----------------------------------------
The detector used was a fast scintillator detector located at an angle of 8
deg. relative to beam trajectory extension and at a flight path of 6.8 m.
The detector was installed in a lead house behind a concrete wall. A conical
hole drilled through the wall acted as a collimator (see Figure 1).
The detector itself consisted of a cylindrical paraterphenyl cristal of 5 cm
diameter and 5 cm height. It was coupled to a FEU-143 photomultiplier.
The time-of-flight measurement is made in the usual inverse method, i.e.
using the detector signal as a start signal and the delayed neutron source
signal as a stop signal. In this way only the useful neutron bursts, i.e.
those producing a signal in the detector are used, so avoiding dead time
losses.
The experimental spectra were corrected for the background effects. To
measure the background neutron spectra, a 1 m long by 18 - 26 cm diameter
iron shadow bar and a 30 cm long borated polyethylene cylinder were placed
between the detector and the sphere (Figure 1).
The estimated uncertainties of the experimental data and their main
components are listed in Table 3. Their dependence on leakage neutron energy
in the case of the smaller shell is shown in Figure 4. During the experiment
the main spectrometer parameters (detector efficiency, absolute normalization
factor, etc.) were measured several times, hence the stability of the
spectrometer could be estimated by calculating the mean square deviation of
individual runs.
Two radioactive reference sources were used, Cf252 for neutron detector
calibration and Pu238 for alpha detector calibration, with their specific
uncertainties. The uncertainties of corrections for Cf-chamber scattering
and time-of-flight conversion to energy, calculated with MCNP, were estimated
at about 1-2%.
In Table 3 the quadratic sum of components 2-5, considered as systematic, is
calculated and its quadratic summation with the statistical uncertainty gives
the total uncertainty of the experimental data.
5. Description of Results and Analysis:
------------------------------------
The measured TOF spectra were corrected for the background effects and
converted into the energy spectrum. The leakage spectrum, L(E), representing
the differential fluence of leakage neutrons, integrated over the full
sphere (4 pi sr) and normalised to 1 source neutron, was then calculated
from the following expression:
L(E)=4*pi*N(E)/(eps(E)*dOmega*Nn)
where:
N(E) = neutron energy spectrum, converted from measured TOF spectra,
eps(E) = neutron detection efficiency (see Ref.[2] for details),
dOmega = detector solid angle (=(pi*r*r)/(L*L), where r is the detector
radius and L the distance from the sphere to the detector),
Nn = number of source neutrons.
The results are presented in Table 4 for vanadium shell No. 1 as leakage
spectrum in terms of neutrons per MeV and per source neutron. For vanadium
shell No. 2 the measured leakage spectrum is presented in Table 5.
MCNP-4C input data for Shells 1 and 2 (5 & 12 cm radius) are given in files
mcnp_r5.inp and mcnp_r12.inp. In the models the spheres and the neutron
source are described precisely, including anisotropic energy and yield
distributions of the T(d,n) source.
For an adequate comparison of measurements and analytical calculation, the
convolution with the spectrometer response function, describing the energy
resolution of the spectrometer, is necessary. It is presented in Table 6.
A correction factor should also be applied before comparing the experimental
spectra with the Monte Carlo time-independent calculations (see Ref. [2]).
The function which should be multiplied with the experimental spectrum is
shown in Figure 5.
Refs. [1] and [2] discuss also the corrections for non-spherical effects,
which should be taken into account in case of 1-dimensional (spherical)
calculations using codes like ANISN, ONEDANT, ANTRA-1 etc.
6. Special Features:
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None
7. Author/Organizer:
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Experiment and Analysis:
S.P. Simakov, B.V. Devkin, B.I. Fursov, M.G. Kobozev, V.A. Talalaiev (Inst.
of Physics and Power Engineering, Obninsk), U. von Moellendorff (Forschung-
zentrum Karlsruhe), M. M. Potapenko (Sci. & Res. Ins. of Organic Materials).
e-mail: simakov@ippe.rssi.ru
or simakov@irs.fzk.de
Compiler of data for Sinbad:
P. Ortego
SEA, Shielding Engineering and Analysis S.L.
Avda. Atenas 75 Las Rozas, 28230 Madrid, Spain
Phone: +3491.631.7807
Fax: +3491.631.8266
e-mail: p.ortego@retemail.es
Reviewer of Compiled Data
I. Kodeli
OECD/NEA, 12 bd. des Iles,
92130 Issy les Moulineaux, France
e-mail: ivo.kodeli@oecd.org
The data were contributed by Dr. S.P. Simakov.
8. Availability:
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Unrestricted
9. References:
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[1] S. P. Simakov et al. "Benchmarking of evaluated nuclear data for
vanadium by a 14 MeV spherical shell transmission experiment"
International data Committee, Report INDC(CCP)-417. October 1998.
[2] S. P. Simakov et al. "Benchmarking of evaluated nuclear data for
vanadium by a 14 MeV spherical shell transmission experiment"
Forschungzentrum Karlsruhe, Report FZKA 6096, 1998.
[3] U. von Moellendorf et al., "A 14-MeV neutron transmission experiment on
vanadium", 19th Symposium on Fusion Technology, Lisbon, 16-20 Sept. 1996.
10. Data and Format:
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No. Filename Size(kb) Content
-- -------- -------- -------
1 ippe_v-a.htm 11 This information file
2 ippe_v-e.htm 27 Experiment Description
3 mcnp_r5.inp 10 MCNP-4C input for V sphere 1 (r=5 cm)
4 mcnp_r12.inp 10 MCNP-4C input for V sphere 2 (r=12 cm)
5 ippefig1.jpg 30 Fig. 1: Experimental setup
6 ippefig2.jpg 26 Fig. 2: 5 and 12 cm radius V spheres
7 ippefig3.jpg 64 Fig. 3: Angular/energy distribution of '14 MeV' source peak
8 ippefig4.jpg 55 Fig. 4: Uncertainties of leakage spectra from V shell 1
9 ippefig5.jpg 44 Fig. 5: Correction for time-of-flight measuring technique
10 indc-ccp-417.pdf 492 IAEA Report
11 fzka-6096.pdf 378 Karlsruhe Report
SINBAD Benchmark Generation Date: 01/2003
SINBAD Benchmark Last Update: 01/2003
