SINBAD ABSTRACT NEA-1517/56
SBE 1.016
SB2 CSEWG Benchmark
1. Name of Experiment: SB2 Experiment on Secondary Gamma-Ray Production Cross Sections Arising from Thermal- Neutron Capture in Each of 14 Different Elements Plus Stainless Steel (1969) 2. Purpose and Phenomena Tested: To improve existing knowledge of gamma-ray spectra arising from thermal-neutron capture in materials important to reactor shielding, especially above 7 MeV. 3. Description of the Source and Experimental Configuration: The Tower Shielding Reactor at ORNL was used as the primary source of neutrons. A spherical lead-water beam shield surrounded the reactor to collimate the neutrons and to reduce background neutrons. Cadmium lined the face of the reactor shield and the collimator to eliminate thermal neutrons. A 2-in.-thick lead disk was inserted in the collimator adjacent to the reactor vessel to reduce the gamma-ray intensity produced by the reactor. A lead collar, 8-in. thick surrounded the collimator exit to reduce capture gamma rays in the cadmium. The profile of the source of thermal neutrons was determined by subtracting a cadmium-covered BF3 detector results from the bare results. The detector was traversed across the vertical and horizontal midplane of the beam at 6 ft from the collimator (without a sample present). Another horizontal traverse across the midplane of the sample space was performed to more accurately map the thermal neutron flux incident on the face of the sample materials. The samples of materials were made of slabs of 4-5 ft square placed into the beam centerline at 45 degrees and 6 ft from the edge of the collimator. The detector was placed at 90 degrees to the reactor beam centerline, 45 degrees with respect to the slab sample normal to reduce to 0.51 MeV or less the reactor-born gamma-rays scattered from the sample. 4. Measurement System and Uncertainties: The 5-inch-diameter x 5-inch long NaI (Tl) crystal was located inside a spherical lead-water shield with 4 lead irises to collimate the gamma-rays. This reduced the background of the gamma rays not born in the sample. A 2-inch.thick borated polyethylene slab covered the outermost iris to reduce thermal-neutron effects in the crystal detector. The detector is placed at 20 ft from and at the midpoint of the sample. The detector viewed the entire slab face and was limited by the addition of two aluminum-walled tanks filled with borated water, lined with borated polyethylene, placed midway between the detector and the sample. 5. Description of Results and Analysis: The experimental results for all 14 elements plus the stainless steel are presented as cross sections versus energy. The minimum energy is 1 MeV to approximately 10 MeV. The standard deviation is +/- 15% and contributions from discrete and cont- inuum gamma rays are included in the results. No transport calculations are necessary for this benchmark, hence no model description, atom densities, etc. are needed. Calculations could simply consist of summing the thermal-neutron absolute capture spectra over appropriate energy intervals, however, it is recommended that a 'standard' ENDF/B photon production group averaging code be used to accomplish this task. The resulting reduced spectral intensities in photons per 100 captures were summed over 0.5-MeV intervals and converted to units of millibarns per capture by using handbook values of the radiative-capture cross section at 0.0253 eV. 6. Special Features: None 7. Author/Organizer: Experiment and analysis: R. E. Maerker and F. J. Muckenthaler, ORNL Compiler of data for SINBAD: H. T. Hunter, ORNL, P.O. Box 2008, Oak Ridge, TN 37831-6362, USA Reviewer of compiled data: J. L. Parsons, ORNL, P.O. Box 2008, Oak Ridge, TN 37831-6362, USA 8. Availability: Unrestricted 9. References: [1] R. E. Maerker and F. J. Muckenthaler "Gamma-Ray Spectra Arising from Thermal Neutron Capture in Elements Found in Soils, Concretes, and Structural Materials," ORNL-4382, UC-34-Physics, August 1969. [2] R. E. Maerker "SB2. Experiment on Secondary Gamma-ray Production Cross Sections Arising from Thermal-Neutron Capture in Each of 14 Different Elements Plus a Stainless Steel," ORNL-TM-5203 ENDF-227 January, 1976. [3] [3] J. D. Court and J. S. Hendricks "Benchmark Analysis of MCNP ENDF/B-VI Iron," LA-12884, UC-700, Dec. 1994 10. Data and Format: Figures: - TSR-II, Sample, Collimator, and Detector Geometry Tables: - 1 Percentage of Beam Intercept 2 - 15 Measured cross section results for materials Fe, SS, N, Na, Al, Cu, Ti, Ca, K, Cl,Si, Ni, Zn, Ba, and S Document is HTML v.3.02 Format with ASCII Tables and Figures in GIF format. SINBAD Abstract Generation Date: 07/98 SINBAD Abstract Last Update: 07/98