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Low-flux neutron imaging

Description: Judicious use of scintillation screens greatly improves the capabilities for low-flux neutron imaging. Room temperature, cooled /sup 6/LiF-- ZnS(Ag) and gadolinium oxysulfide (Gd/sub 2/O/sub 2/S: Tb) were evaluated for direct exposures, and x-ray intensifying screens were evaluated with dysprosium and europium transfer screens. Although gadolinium oxysulfide provides improved resolution, it requires seven times the imaging time of /sup 6/LiF-- ZnS(Ag). Studies indicate that use of intensifying screens during transfer processes decreases the flux for a given density by about 30% and provides contrast enhancement. It was shown that cooling of scintillator-film combinations reduces reciprocity failure effects and in these experiments decreased direct exposure times (Gd/sub 2/O/sub 2/S: Tb) by up to 80%. (auth)
Date: September 1, 1973
Creator: Swinth, K.L. & Nichols, L.L.
Partner: UNT Libraries Government Documents Department

Automated phantom assay system

Description: This paper describes an automated phantom assay system developed for assaying phantoms spiked with minute quantities of radionuclides. The system includes a computer-controlled linear-translation table that positions the phantom at exact distances from a spectrometer. A multichannel analyzer (MCA) interfaces with a computer to collect gamma spectral data. Signals transmitted between the controller and MCA synchronize data collection and phantom positioning. Measured data are then stored on disk for subsequent analysis. The automated system allows continuous unattended operation and ensures reproducible results.
Date: November 1, 1991
Creator: Sisk, D.R.; Nichols, L.L. & Olsen, P.C.
Partner: UNT Libraries Government Documents Department

Description and evaluation of the Hanford personnel dosimeter program from 1944 through 1989. [Contain Glossary]

Description: This report describes the evolution of personnel dosimeter technology at Hanford since the inception of Hanford operations in 1944. Each of the personnel dosimeter systems used by people working or visiting Hanford is described. In addition, the procedures used to calibrate and calculate dose for each of the dosimeter systems are described. The accuracy of the recorded dose, primarily whole body deep dose, for the different dosimeter systems is evaluated. The evaluation is based on an extensive review of historical literature, as well as a 1989 intercomparison study of all film dosimeters and performance testing of the thermoluminescent dosimeter, also conducted during 1989. 73 refs., 40 figs., 41 tabs.
Date: September 1, 1990
Creator: Wilson, R.H.; Fix, J.J.; Baumgartner, W.V. & Nichols, L.L.
Partner: UNT Libraries Government Documents Department

Automated phantom assay system

Description: This paper describes an automated phantom assay system developed for assaying phantoms spiked with minute quantities of radionuclides. The system includes a computer-controlled linear-translation table that positions the phantom at exact distances from a spectrometer. A multichannel analyzer (MCA) interfaces with a computer to collect gamma spectral data. Signals transmitted between the controller and MCA synchronize data collection and phantom positioning. Measured data are then stored on disk for subsequent analysis. The automated system allows continuous unattended operation and ensures reproducible results.
Date: November 1, 1991
Creator: Sisk, D. R.; Nichols, L. L. & Olsen, P. C.
Partner: UNT Libraries Government Documents Department

Response characteristics of selected personnel neutron dosimeters

Description: Performance characteristics of selected personnel neutron dosimeters in current use at Department of Energy (DOE) facilities were determined from their evaluation of neutron dose equivalent received after irradiations with specific neutron sources at either the National Bureau of Standards (NBS) or the Pacific Northwest Laboratory (PNL). The characteristics assessed included: lower detection level, energy response, precision and accuracy. It was found that when all of the laboratories employed a common set of calibrations, the overall accuracy was approximately +-20%, which is within uncertainty expected for these dosimeters. For doses above 80 mrem, the accuracy improved to better than 10% when a common calibration was used. Individual differences found in this study may reflect differences in calibration technique rather than differences in the dose rates of actual calibration standards. Second, at dose rates above 100 mrem, the precision for the best participants was generally below +-10% which is also within expected limits for these types of dosimeters. The poorest results had a standard deviation of about +-25%. At the lowest doses, which were sometimes below the lower detection limit, the precision often approached or exceeded +-100%. Third, the lower level of detection for free field /sup 252/Cf neutrons generally ranged between 20 and 50 mrem. Fourth, the energy dependence study provided a characterization of the response of the dosimeters to neutron energies far from the calibration energy. 11 references, 22 figures, 26 tables.
Date: September 1, 1983
Creator: McDonald, J.C.; Fix, J.J.; Hadley, R.T.; Holbrook, K.L.; Yoder, R.C.; Roberson, P.L. et al.
Partner: UNT Libraries Government Documents Department