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ENDF/B-VI Cross-Section Validation/MCNP - Validation

1. Name of Experiment:

University of Illinois Iron Sphere Benchmark (1975)

2. Purpose and Phenomena Tested:

The purpose of this experiment was to compare measurements and calculations of 
fast-neutron leakage spectra from a spherical shell of iron to test the validity and
accuracy of the neutron cross-section data.

3. Description of the Source and Experimental Configuration:

Two sources were used: (1) a californium-252 spontaneous fission source, and (2) a 
D-T fusion neutron source provided by a neutron generator. For the measurements 
using the D-T source, the flight tube of the neutron generator was inserted through 
a 9.5 cm diameter re entrant hole. For the measurements using the Cf-252 source, the
reentrant hole was plugged with a steel cylinder, and the Cf-252 source was hung 
from a small steel holder attached to the plug. The holder positioned the Cf-252 
source at the center of the iron sphere. 

The iron sphere and the neutron detector were both situated 1 meter above the 
concrete floor with the detector positioned 200 cm from the center of the sphere.

The iron sphere contained 0.21% by weight of carbon and 0.47% by weight of 
manganese. The spherical shell of iron had an inner radius of 7.65 cm, an outer 
radius of 38.10 cm, and a number density of 0.0849 nuclei/barn-cm.

4. Measurement System and Uncertainties:

The neutron spectrum measurements were made with a 5 cm x 5 cm glass-encapsulated 
NE-213 scintillator. The proton-recoil spectrometry system was chosen because it 
does not require an elaborate pulsed neutron source.

The total estimated systematic error in the normalization of the measurements is 8% 
standard deviation for a Cf-252 source within the iron spherical shell. 

5. Description of Results and Analysis:

The energy range between 1.0 and 15 MeV was covered by the NE-213 scintillator. 
Background contributions to the recoil spectra were measured by placing a paraffin 
shadow cone midway between the detector and the spherical assembly.

The spectra were unfolded by the FORIST computer code, which is a modified version 
of the COOLC and FERDoR computer codes. These modifications resulted in unfolded 
spectra having optimized energy resolution and increased accuracy through the use of
an iterative smoothing technique.

The ANISN one-dimensional discrete ordinates neutron transport code was used to 
calculate the leakage spectra. 

6. Special Features:


7. Author/Organizer:

Experiment and Analysis:
    Richard Harold Johnson, Nuclear Engineering Program, University of Illinois at 
    Urbana-Champaign, Urbana, IL

Compiler of data for SINBAD:
    Jennifer Parsons, Radiation Shielding Information Center, Oak Ridge National 
    Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6362

Reviewer of compiled data:
    Hamilton Hunter, Radiation Shielding Information Center, Oak Ridge National 
    Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6362, fax 423-574-6182, e-mail 

8. Availability:


9. References:

[1] R.H. Johnson, "Integral Tests of Neutron Cross Sections for Iron, Nobium, 
    Beryllium, and Polyethylene," PhD Thesis, University of Illinois at Urbana-
    Champaign (1975)
[2] N.E. Hertel, R.H. Johnson, B.W. Wehring, and J.J. Dorning, "Transmission of Fast
    Neutrons Through an Iron Sphere," Fusion Technology, 9, 345-361 (Mar 1986)
[3] M.L. Williams, C. Aboughantous, M. Asgari, J.E. White, R.Q. Wright and F.B.K. 
    Kam, "Transport Calculations of Neutron Transmission Through Steel Using 
    ENDF/B-V, Revised ENDF/B-V, and ENDF/B-VI Iron Evaluations," Annual Nuclear 
    Energy, 18, 549-565 (1991)
[4] D.T. Ingersoll, "Integral Testing of Neutron Cross Sections Using Simultaneous 
    Neutron and Gamma-Ray Measurements," PhD Thesis, University of Illinois at 
    Urbana-Champaign (1977)
[5] N.E. Hertel, "High-Energy Neutron Transport Through Tungsten and Iron," PhD
    Thesis, University of Illinois at Urbana-Champaign (1979)

10. Data and Format:

    (1) 47-group Cf-252 fission spectrum
    (2) 199-group CF-252 fission spectrum
    (3) 47-group D-T source (5% D-D)
    (4) 199-group D-T source (5% D-D)
    (5) Physical Properties of the Iron Spherical Shell
    (6) Leakage Spectrum from the Iron Sphere containing D-T source

    (1) Physical Arrangement for the iron sphere
    (2) Background Contributions Layout
    (3) Leakage Spectra for Cf-252 source in iron sphere
    (4) Leakage Spectra for D-T source in iron sphere

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SINBAD Abstract Generation Date: 06/98
SINBAD Abstract Last Update: 08/06