SINBAD ABSTRACT NEA-1517/57
SBE 1.015

CSEWG Benchmark (1969)

1. Name of Experiment:

SB3. Experiment on Secondary Gamma-Ray Production Cross Sections Averaged Over a
Fast-Neutron Spectrum for Each of 13 Different Elements Plus a Stainless Steel -1969

2. Purpose and Phenomena Tested:

This experiment was performed to improve existing knowledge of secondary gamma-ray 
production cross sections arising from fast-neutron interactions in different 
shielding materials.

3. Description of the Source and Experimental Configuration:

The neutron source was the Tower Shielding Reactor (TSR-II) at the Tower Shielding
Facility located in Oak Ridge National Laboratory. The incident neutron spectrum 
was between 1 and 14 MeV. A spherical lead-water beam shield surrounded the reactor 
to collimate the neutrons and to reduce background. Cadmium lined the face of the 
reactor shield and the collimator to eliminate thermal neutron scattering. A 
2-inch-thick lead disk was inserted in the collimator adjacent to the reactor 
vessel to reduce the gamma-ray intensity. A 8-inch-thick lead collar, containing a 
15-inch-diameter hole, surrounded the collimator exit to reduce capture gamma-rays 
in the cadmium.

The absolute spectra of the low-energy neutrons incident on the slab samples 
through the boron and cadmium filters were measured using a Blosser spectrometer 
in the bare beam, in conjunction with beam mappings using a bare and cadmium-
covered BF3 detector.

Measurements were made with samples of natural iron, oxygen, aluminum, copper, zinc, 
titanium, potassium, calcium, sodium, silicon, nickel, barium, sulfur, and type-321 
stainless steel. The slab samples were 4 to 5 ft square with thicknesses between 
1/16 and 4 in. The samples were placed vertically in the beam centerline at an angle
of 45 deg. and at a mean distance of 6 ft from the edge of the reactor shield.

4. Measurement System and Uncertainties:

Measurements were made using a single-crystal spectrometer placed so that the 
detector collimator was at an angle of 90 deg. to the reactor beam collimator, 45 
deg. with respect to the slab sample normal. The spectrometer was a 5-in.-diameter 
by 5-in.-long NAI(Tl) crystal located inside a spherical lead-water shield. The 
crystal was placed 20 ft from the midpoint of the reactor and had the ability to 
view the entire transmitting face of the slab. This geometry minimized the 
incidence of reactor gamma rays on the crystal. The NaI crystal yielded energy 
resolutions which varied from 6.2% at 1.38 MeV (FWHM) to 2.5% at 10.83 MeV. 

Two gamma-ray spectra were measured for each sample. One was obtained by placing a 
2.13-cm-thick boron filter over the reactor collimator, and the other was obtained 
with a 30-mil-thick cadmium filter placed over the collimator.

5. Description of Results and Analysis:

The experimental data are differential in the gamma-ray energy from approximately 
1 to 6.5 MeV and are expressed as values of 4*PI times the differential gamma-ray 
production cross section in millibarns at 90 deg. to the incident neutron beam 
averaged over a neutron source lying above 1 MeV. The gamma-ray production 
measurements are accurate to +/- 30% and include the contributions from both 
discrete and continuum gamma rays. No transport calculations are necessary for 
this benchmark, hence model description, atom densities, etc. are not needed. It 
is recommended that a 'standard' ENDF/B photon production group averaging code be 
used to determine the production cross sections. 

Each slab sample was either in metal or powder form, and all but one of the powder 
samples was a compound. Some of the samples also contained impurities, which are 
given in weight percentages.

6. Special Features:

None

7. Author/Organizer:

Experiment and Analysis:
    R.E. Maerker and F.J. Muckenthaler, ORNL

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
    h3o@ornl.gov

8. Availability:

Unrestricted

9. References:

[1] R.E. Maerker, "SB3. Experiment on Secondary Gamma-Ray Production Cross Sections 
    Averaged Over a Fast-Neutron Spectrum for Each of 13 Different Elements Plus a 
    Stainless Steel," ORNL-TM-5204 (ENDF-228), Oak Ridge National Laboratory
    (January 1976)
[2] R.E. Maerker and F.J. Muckenthaler, "Gamma-Ray Spectra Arising from Fast-Neutron
    Interactions in Elements Found in Soils, Concretes, and Structural Materials," 
    ORNL-4475, Oak Ridge National Laboratory (1969)
[3] R.E. Maerker and F.J. Muckenthaler, "Gamma-Ray Spectra Arising from Fast-Neutron
    Interactions in Elements Found in Soils, Concretes, and Structural Materials," 
    Nuclear Science and Engineering: 42, 335-351 (1970)

10. Data and Format:

Tables:
    (1) Comparison of neutron spectra through the boron and cadmium filters
    (2) Description of slab samples analyzed
    (3)-(17) A. Gamma-ray production measurements for all 14 materials
             B. Tabulated relative fast-neutron spectrum

Figures:
    (1) Schematic diagram of the geometry
    (2) Neutron spectrum from boron-filtered beam
    (3) Neutron spectrum from cadmium-filtered beam
    (4) Fast-neutron spectrum from boron-filtered beam


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SINBAD Abstract Generation Date: 07/98

SINBAD Abstract Last Update: 07/98