NEA-1553/27

SINBAD ABSTRACT NEA-1553/27
SBE 4.001

IAEA FENDL/Fusion Benchmark

1. Name of the Experiment:

SB5: ORNL 14-MeV Neutron Stainless-Steel/Borated Polyethylene Slab Experiment (1979)

2. Purpose and Phenomena Tested:

The experimental facility was built at Oak Ridge National Laboratory, building 6025, for the express purpose of conducting fusion reactor shielding experiments. The experiment contains shield configurations, which consisted of stainless steel or stainless steel and borated polyethylene slabs, was designed to measure neutron and gamma-ray spectra behind those shields due to 14-MeV neutrons incident on the shields. Provisions were made for measuring data for shields up to one meter thick, although the thickest measured was about 57 cm thick. The data obtained from the experiment could be used to test methods and data used in calculating neutron and gamma-ray transmission through fusion reactor shields having similar material compositions.

3. Description of the Source and Experimental Configuration:

The design of the facility and source was based upon a preconstruction computer analysis using the 2-Dimensional radiation transport code DOT. The room housing the experimental apparatus is roughly 7 m by 9 m lined with 92-cm-thick concrete personnel shields. In an adjacent room, an accelerator is connected via a drift tube to the target assembly for the neutron source generation. A large concrete test shield support structure, supports the test slab materials and reduces the background scattered radiation and was located toward the center of the room.

The source for the experiment was provided by a Sames Accelerator which directed 250-keV deuterons onto a 4 mg/cm² titanium titride target. Neutrons with energies averaging about 14 MeV were produced with various energies and angles. A program used to calculate the source is shown in the full description of the SBE. The shield slabs are 152.4-cm square (R_eq=85.98 cm), but in the model they radially fill the 156.21-cm × 172.72-cm cavity (R_eq=92.67 cm). An additional thermal-neutron shield was placed behind the detectors to decrease the effect of neutron backscatter from and gamma-ray production in the concrete wall behind the detector. Six different shield configurations, housing various thicknesses and arrangements of stainless steel and/or borated polyethylene slabs, were tested with an additional configuration containing no test slabs ("no-shield" case). A total of sixty-four neutron and gamma-ray spectra were published. Data for three of the neutron measurements were thought unreliable but are included for completeness.

4. Measurement System and Uncertainties.

Measurements were made with an NE-213 detector manufactured at the Oak Ridge National Laboratory. Neutron and gamma-ray responses were distinguished through pulse-shape discrimination. The measured data were unfolded with the FERD code, and results were reported as point data on a fine energy grid and for a two standard deviation band about the mean values. The uncertainties are not necessarily the uncertainties of the measurements. Quoted uncertainties for the maximum shield thickness examined include: NE-213 efficiency (5%), alpha calibration (3%), neutron detector position (1%), nine stainless steel slabs (3%), and two borated polyethylene slabs (1%). The detector resolutions for the NE-213 measurements are given as:

for neutrons of energy E_n MeV and

for gamma rays of energy E_gamma MeV, where R_N and R_gamma are the full width at half maximum values (in percent) of the detector response to neutrons and gamma rays, respectively.

5. Description of Results and Analysis:

The various measurements are described using an x-y-z coordinate location of the detector position, the configuration of material slabs and whether it is a gamma or neutron measurement. Data for runs R148NS.008, C171NS.016, and C171GS.012 are considered unreliable, as repeated measurements were substantially different and more consistent with other results. The normalized spectra (MeV^-1 cm^-2) per source neutron and energy structure are tabulated and plotted for a total of 64 measurements, behind 7 configurations, at up to 10 different angles or lateral (z positions).

6. Special Features:

Relatively high-energy neutron source. Significant data base of gamma-ray measurements.

7. Author/Organizer/Compiler:

Authors:

G. T. Chapman, G. L. Morgan, J. W. McConnell, R. T. Santoro, J. M. Barnes,

R. G. Alsmiller, Jr., and E. M. Oblow. Oak Ridge National Laboratory

Compiler:

C. O. Slater, Oak Ridge National Laboratory, Oak Ridge, Tennessee USA 37831-6363.

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:

All data are included with the benchmark. Access is unrestricted.

9. References:

1. G. T. Chapman, G. L. Morgan, and J. W. McConnell, "The ORNL Integral Experiment to Provide Data for Evaluating Magnetic-Fusion-Energy Shielding Concepts, Part I: Attenuation Measurements", ORNL/TM/7356 (August 1982).

2. R. T. Santoro, J. M. Barnes, R. G. Alsmiller, Jr., and E. M. Oblow, "Calculational Procedures for the Analysis of Integral Experiments for Fusion Reactor Design", ORNL-5777 (July 1981).Oak Ridge National Laboratory, Oak Ridge, Tennessee USA 37831

3. Philip F. Rose and R. W. Roussin, eds., "SB5: Fusion Reactor Shielding Benchmark," in CROSS SECTION EVALUATION WORKING GROUP BENCHMARK SPECIFICATIONS VOLUME II SUPPLEMENT, Brookhaven National Laboratory Report BNL 19302, Vol. II (September 1986) (also ENDF-202).

10. Data and Format:

Tables:

ASCII Text Format

Table 1 - Energy and Angular Distribution of the Source

Table 2 - Region Boundaries for Full Two-Dimensional Model of the Experiment

Table 3 - Material Compositions for the Analysis of the Experiment

Tables 4 through 69 - Tabular Results of Detector Measurements Behind Mockups

Figures:

Figure 1 - Experimental Arrangement (GIF Image)

Figure 2 - Three-Dimensional View of the Experimental Enclosure

Figure 3 - Schematics of Experimental Arrangement

Figure 4 - Two-Dimensional Calculational Model of Experiment