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dc.rights.licenseRestricted to current Rensselaer faculty, staff and students. Access inquiries may be directed to the Rensselaer Libraries.
dc.contributorLiu, Li (Emily)
dc.contributorDanon, Yaron
dc.contributorBrown, Ethan
dc.contributorJi, Wei
dc.contributor.authorWendorff, Carl
dc.date.accessioned2021-11-03T09:07:23Z
dc.date.available2021-11-03T09:07:23Z
dc.date.created2019-02-20T13:24:20Z
dc.date.issued2018-12
dc.identifier.urihttps://hdl.handle.net/20.500.13015/2344
dc.descriptionDecember 2018
dc.descriptionSchool of Engineering
dc.description.abstractThermal neutron scattering theory is outlined in Chapter 2. The thermal scattering law (TSL) defines the dynamic structure factor, S(α,β). It is defined as the mathematical representation of the physical structure, chemical bond, and thermal motion. Three experiments were completed at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory. These experiments utilized two time-of-flight neutron spectrometers, ARCS and SEQUOIA, to collect the double differential scattering cross section (DDSCS) of the material tested. The DDSCS is the fundamental kernel of particle scattering as defined in the Boltzmann transport equation and directly related to the S(α,β). No analytical solution to the S(α,β) equation exists for most situations. Nuclear data files are created for each material with numerical approximations of it. The current Evaluated Nuclear Data File (ENDF) release, ENDF/B-VIII.0, contain data sets for many important materials.
dc.description.abstractLastly, this work explored the feasibility of using the experimental DDSCS to directly create representative S(α,β) libraries. The process was able to create workable files, but the product did not improve the representation of the DDSCS and identified issues that to resolve would require just as much convolution as done in the previous standard process.
dc.description.abstractA model of the experiments was created in MCNP 6.1 [2]. This was used to compare the ENDF/B-VIII.0 and other S(α,β) data library files with the experimentally collected DDSCS data. The S(α,β) libraries were also compared with MCNP 6.1 models of criticality benchmarks that were found in the International Criticality Safety Benchmark Project (ICSBEP) Handbook. The effects of the S(α,β) libraries were measured by comparing the changes in the criticality, keff , of the system. This allows the libraries to be compared with both differential measurements (DDSCS experiments) and integral measurements (experimentally collected keff ). The H2O and CH2 libraries display good to great representation of both, the experimental DDSCS and keff . The ENDF/B-VIII.0 SiO2 and C5O2H8 libraries show limited ability to represent the experimental data and in some cases were surpassed by a new S(α,β) libraries created at RPI. There does not exist a current S(α,β) library or corresponding criticality benchmarks for Teflon.
dc.description.abstractThe standard used in current literature for the thermal neutron scattering approximation in concrete was to use liquid H2O. Hydrogen scattering does represent the highest probability for scattering with an incident neutron. Unlike in H2O, the hydrogen was bound in a matrix within the solid concrete. Possible replacements in ice (solid H2O) and CH2 are explored. The process outlined for validating the S(α,β) libraries was used and found that ice did the best representation of the DDSCS, while both ice and CH2 improved on liquid H2O when testing the effects on criticality benchmarks.
dc.description.abstractThe current generation of electric power nuclear reactors all operate in the thermal energy region. This corresponds with the ideal range of fission probability for U-235. As long as fission processes and products need to be utilized and contained, neutron moderators are going to be needed in large amounts to remove the kinetic energy of the neutrons. Simulations of reactor vessels and subsystems of the nuclear power plant have progressed to the point that precision of the nuclear data inputted into the model represented a nontrivial source of system uncertainty. To determine the representation of thermal neutron scattering in neutron moderators and important materials, experiments were completed and simulations tested the viability of the current thermal scattering law nuclear data library.
dc.description.abstractSix materials were experimented on, light water (H2O), polyethylene (CH2), quartz (SiO2), Lucite (C5O2H8), Teflon ((CF4)n), and concrete. The data represents the first of its kind for SiO2, C5O2H8, Teflon, and concrete. Other experimental data sets exist for H2O and CH2, but mostly do not contain the range of energies achieved in this work at the SNS.
dc.language.isoENG
dc.publisherRensselaer Polytechnic Institute, Troy, NY
dc.relation.ispartofRensselaer Theses and Dissertations Online Collection
dc.subjectNuclear engineering
dc.titleValidation and benchmarking of the thermal neutron scattering law data files for neutron moderators using experimental data
dc.typeElectronic thesis
dc.typeThesis
dc.digitool.pid179485
dc.digitool.pid179486
dc.digitool.pid179487
dc.rights.holderThis electronic version is a licensed copy owned by Rensselaer Polytechnic Institute, Troy, NY. Copyright of original work retained by author.
dc.description.degreePhD
dc.relation.departmentDept. of Mechanical, Aerospace, and Nuclear Engineering


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