Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references (leaves 114-115).Issued also on microfiche from Lange Micrographics.Three drums containing potentially contaminated lead bricks were assayed with the Segmented Gamma Scan Neutron Assay System (SGSNAS) at Pacific Northwest National Laboratory's (PNNL) Nondestructive Assay Center. The assay system reported that the drums contained transuranic material. These results were based solely on the number of time-correlated neutron events. The gamma spectra for all three drums were inspected and no gamma ray lines corresponding to transuranic nuclides were found. Further investigations found that the lead in one of the drums had not been part of a contaminated area cleanup and should not be radiologically contaminated. This thesis examines the nuclear reactions that produce neutrons, the principles of neutron detectors including the circuitry required for coincidence counting, and how neutrons interact with matter. The premise is that time-correlated neutrons are produced from high-energy muon interactions with the lead nucleus, a spallation reaction. Muons are a component of the "air shower cascade" as cosmic rays traverse through the earth's atmosphere; therefore, an extensive study of cosmic rays has been undertaken. Verification that time-correlated neutrons are emitted from lead was performed using three completely separate systems
