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Assessment of Cosmic Background Attenuation at Building 3425 (Underground Laboratory)

Description: Specifications for the Underground Facility (building 3425) in the Radiation Detection and Nuclear Sciences complex presently under construction at Pacific Northwest National Laboratory mandate a 30 meters water equivalent shielding for cosmic background attenuation at the 30-foot underground depth of the laboratory. A set thickness of a specified fill material was determined; however a smaller thickness of a higher density material was used for the earthen bunker. Questions arose as to whether this altered configuration met the required shielding specifications. A series of measurements were made to address this concern using a 4”x4”x16” NaI(Tl) detector (Scionix Holland, 3.5N-E2-X). Cosmic ray data were taken at the surface, and at several locations within the underground facility in order to obtain an experimental value for the attenuation of the cosmic radiation. This experimental result was compared with the contracted attenuation.
Date: October 1, 2009
Creator: Kouzes, Richard T.; Borgardt, James D.; Lintereur, Azaree T. & Panisko, Mark E.
Partner: UNT Libraries Government Documents Department

Muon Fluence Measurements for Homeland Security Applications

Description: This report focuses on work conducted at Pacific Northwest National Laboratory to better characterize aspects of backgrounds in RPMs deployed for homeland security purposes. Two polyvinyl toluene scintillators were utilized with supporting NIM electronics to measure the muon coincidence rate. Muon spallation is one mechanism by which background neutrons are produced. The measurements performed concentrated on a broad investigation of the dependence of the muon flux on a) variations in solid angle subtended by the detector; b) the detector inclination with the horizontal; c) depth underground; and d) diurnal effects. These tests were conducted inside at Building 318/133, outdoors at Building 331G, and underground at Building 3425 at Pacific Northwest National Laboratory.
Date: August 10, 2010
Creator: Ankney, Austin S.; Berguson, Timothy J.; Borgardt, James D. & Kouzes, Richard T.
Partner: UNT Libraries Government Documents Department

Skyshine Contribution to Gamma Ray Background Between 0 and 4 MeV

Description: Natural gamma-ray background is composed of four components; which include cosmic rays, cosmic ray produced atmospheric activity, terrestrial sources, and skyshine from terrestrial sources. Skyshine is radiation scattered from the air above a source that can produce a signal in radiation detection instrumentation. Skyshine has been studied for many years but its contribution to the natural background observed in a detector has not been studied. A large NaI(Tl) detector was used to investigate each of the four components of the natural background using a series of 48-hour measurements and appropriate lead shielding configured to discriminate contributions from each component. It was found that while the contribution from skyshine decreases rapidly with energy, it represents a significant portion of the background spectrum below ~500keV. A similar campaign of measurements using a HPGe detector is underway.
Date: August 14, 2009
Creator: Mitchell, Allison L.; Borgardt, James D. & Kouzes, Richard T.
Partner: UNT Libraries Government Documents Department