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Gamma spectrometry and calibration methods used in neutron dosimetry

Description: Neutron activation rates are calculated from measured gamma-ray spectral data obtained from calibrated lithium drifted germanium (Ge(Li)) detectors. The calibration techniques, which include energy, efficiency, pulse height analyzer data reduction, and geometry factors, are discussed. Problems encountered when analyzing highly radioactive samples, specifically random coincidence summing, sample size, air absorption, and use of absorbers, are also discussed briefly. To illustrate the accuracy achievable, the reduction of gamma-ray spectral data and the calculation of reaction rates by three independent laboratories are presented for both fission and nonfission foils to a precision of +-1 to 2% (1sigma). The application of these neutron activation rates to neutron dosimetry is discussed. An unfolded neutron spectrum is illustrated, along with energy sensitivity limits for many reactions of dosimetry interest.
Date: January 1, 1979
Creator: Malewicki, R.L.; Heinrich, R.R. & Popek, R.J.
Partner: UNT Libraries Government Documents Department

Fast neutron damage in germanium detectors

Description: The effects of fast neutron radiation damage on the performance of both Ge(Li) and Ge(HP) detectors have been studied during the past decade and will be summarized. A review of the interaction processes leading to the defect structures causing trapping will be made. The neutron energy dependence of observable damage effects will be considered in terms of interaction and defect production cross sections.
Date: October 1, 1979
Creator: Kraner, H.W.
Partner: UNT Libraries Government Documents Department

Critical concentrations of cadmium in human liver and kidney measured by prompt-gamma neutron activation

Description: Few data exist on Cd metabolism in human beings. In particular, data are needed on the role of parameters such as age, sex, weight, diet, smoking habits, and state of health. Prompt-gamma neutron activation analysis (PGNAA) provides the only currently available means for measuring in vivo levels of liver and kidney Cd. The method employs an 85 Ci, /sup 235/Pu,Be neutron source and a gamma ray detection system consisting of two Ge(Li) detector. The dose delivered to the liver and left kidney is 666 mrem (detection limit is 1.4 ..mu..g/g Cd in the liver and 2.0 mg Cd for one kidney). Absolute levels of Cd in the kidney and concentrations of Cd in the liver were measured in vivo in twenty healthy adult males using /sup 238/Pu,Be neutron sources. Organ Cd levels of smokers were significantly elevated above those of nonsmokers. Biological half-time for Cd in the body was estimated to be 15.7 yr. Cigarette smoking was estimated to result in the absorption of 1.9 ..mu..g of Cd per pack. No relationship was bound between body stores of Cd (liver and kidney) and Cd or ..beta..-microglobulin levels in urine and blood. Currently the above neutron activation facility is being mounted on a 34-ft mobile trailer unit. This unit will be used to monitor levels of Cd in industrial workers. It is anticipated that critically important data, particularly on industrially exposed workers, will provide a better basis for determining critical concentrations and for the setting or revision of standards for industrial and environmental Cd pollution. (ERB)
Date: January 1, 1979
Creator: Cohn, S.H.; Vartsky, D.; Yasumura, S.; Zanzi, I. & Ellis, K.J.
Partner: UNT Libraries Government Documents Department