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Author: Thomas Martin Publisher: ISBN: Category : Languages : en Pages :
Book Description
The measurement of the distribution of kinetic energy carried by neutron particles is of interest to the health physics and radiation protection industry. Neutron particle spectral fluence is essential to the calculation of absorbed dose, equivalent dose, and other dosimetric quantities . Current methods of neutron spectrometry require either a large number of individual measurements and a priori spectral information, or complex and delicate equipment. To reduce these deficiencies, a novel neutron spectrometer, consisting of plastic scintillating fibers in a hexagonal array, was simulated via Monte Carlo. Fiber size and boron content were varied to optimize response characteristics. The results were compared to industry standard multi-sphere spectrometers. Of the geometries and materials analyzed, it was found that smaller diameter fibers with 1% loading of natural boron provide the best efficiency and energy resolution. Energy resolution was found to be similar to multi-sphere spectrometers, with the ability to differentiate on the order of ten energy fluence groups. Near isotropic angular response was traded for significantly reduced detection time and increased simplicity. Spectral analysis of individual fiber response can provide directional information based on the ratio of energy deposition by thermal neutrons to all neutrons. Future work using proton recoil spectral data from individual fibers will allow increases in energy resolution while reducing or eliminating the need for a priori spectral information.
Author: Thomas Martin Publisher: ISBN: Category : Languages : en Pages :
Book Description
The measurement of the distribution of kinetic energy carried by neutron particles is of interest to the health physics and radiation protection industry. Neutron particle spectral fluence is essential to the calculation of absorbed dose, equivalent dose, and other dosimetric quantities . Current methods of neutron spectrometry require either a large number of individual measurements and a priori spectral information, or complex and delicate equipment. To reduce these deficiencies, a novel neutron spectrometer, consisting of plastic scintillating fibers in a hexagonal array, was simulated via Monte Carlo. Fiber size and boron content were varied to optimize response characteristics. The results were compared to industry standard multi-sphere spectrometers. Of the geometries and materials analyzed, it was found that smaller diameter fibers with 1% loading of natural boron provide the best efficiency and energy resolution. Energy resolution was found to be similar to multi-sphere spectrometers, with the ability to differentiate on the order of ten energy fluence groups. Near isotropic angular response was traded for significantly reduced detection time and increased simplicity. Spectral analysis of individual fiber response can provide directional information based on the ratio of energy deposition by thermal neutrons to all neutrons. Future work using proton recoil spectral data from individual fibers will allow increases in energy resolution while reducing or eliminating the need for a priori spectral information.
Author: Simon R. Bolding Publisher: ISBN: Category : Languages : en Pages :
Book Description
Simulations were performed using MCNP5 to optimize the geometry of a neutron spectrometer. The cylindrical device utilizes micro-structured neutron detectors encased in polyethylene moderator to identify sources based on energy spectrum. Sources are identified by comparison of measured detector responses to predetermined detector response templates that are unique to each neutron source. The design of a shadow shield to account for room scattered neutrons was investigated as well. For sufficient source strength in a void, the optimal geometric design was able to detect all sources in 1000 trials, where each trial consists of simulated detector responses from 11 unique sources. When room scatter from a concrete floor was considered, the shadow shield corrected responses were capable of correctly identifying 96.4% of the simulated sources in 1000 trials using the same templates. In addition to spectrometer simulations, a set of neutron multiplicity experiments from a plutonium sphere with various reflector thicknesses were simulated. Perturbations to nuclear data were made to correct a known discrepancy between multiplicity distributions generated from MCNP simulations and experimental data. Energy-dependent perturbations to the total number of mean neutrons per fission [average velocity] of 239Pu ENDF/B-VII. 1 data were analyzed. Perturbations were made using random samples, correlated with corresponding covariance data. Out of 500 unique samples, the best-case [average velocity] data reduced the average deviation in the mean of multiplicity distributions between simulation and experiment to 4.32% from 6.73% for the original data; the average deviation in the second moment was reduced from 13.87% to 8.74%. The best-case [average velocity] data preserved k[subscript]e[subscript]f[subscript]f with a root-mean-square deviation (RMSD) of 0.51% for the 36 Pu cases in the MCNP validation suite, which is comparable to the 0.49% RMSD produced using the original nuclear data. Fractional shifts to microscopic cross sections were performed and multiplicity and criticality results compared. A 1.5% decrease in fission cross section was able to correct the discrepancy in multiplicity distributions greater than the [average velocity] perturbations but without preserving k[subscript]e[subscript]f[subscript]f.
Author: Edward K. Kropp Publisher: ISBN: Category : Neutron counters Languages : en Pages : 94
Book Description
A self-powered neutron detector (SPND) is a device that, coupled with a current meter, provides a readout proportional to neutron population. This thesis discusses the design parameters of an array of such devices, their characteristics, and the use of these devices as a self-powered neutron spectrometer (SPNS) to provide information about the energy distribution in a neutron radiation field. Neutron absorption in an appropriate material produces subsequent beta emissions. In a SPND, some of these beta particles will cross a non-conducting region and stop in a collector material. A net exchange of charge between these regions can be read as a current flowing between the emission region and the collector region. One potential SPNS design was modeled using a Monte Carlo simulation of the device's interaction with a radiation field. The Monte Carlo program used predicts the beta flux which is proportional to the current that would be produced by an actual device. Various beta emitting materials were considered for this device, and a sensitivity study of each was included. The design considered is comprised of a concentric set of these cylindrical SPND detector elements which, in themselves, are currently available technology.
Author: Publisher: ISBN: Category : Nuclear energy Languages : en Pages : 992
Book Description
NSA is a comprehensive collection of international nuclear science and technology literature for the period 1948 through 1976, pre-dating the prestigious INIS database, which began in 1970. NSA existed as a printed product (Volumes 1-33) initially, created by DOE's predecessor, the U.S. Atomic Energy Commission (AEC). NSA includes citations to scientific and technical reports from the AEC, the U.S. Energy Research and Development Administration and its contractors, plus other agencies and international organizations, universities, and industrial and research organizations. References to books, conference proceedings, papers, patents, dissertations, engineering drawings, and journal articles from worldwide sources are also included. Abstracts and full text are provided if available.
Author: Thomas Martin
Author: Thomas Martin
Author: Simon R. Bolding
Author: Edward K. Kropp
Author: James Elroy Leiss
Author: W. Brown
Author: Mohamed Luis El-Sheikh
Author: Manoj Kumar Parida
Author: Bertel Grimeland
Author: R. Walker
Author: