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Title Assessment of Reactivity Equivalence for Enhanced Accident Tolerant Fuels in Light Water Reactors
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Publication Date
Degree Level doctoral
University/Publisher University of Tennessee – Knoxville
Abstract The neutronic behavior of accident tolerant fuel (ATF) concepts was simulated in light water reactors (LWRs) to establish design parameters to match reactivity lifetime requirements of standard UO2 [uranium dioxide]/Zircaloy fuel. The two concepts discussed in this dissertation are fully ceramic micro-encapsulated (FCM) fuel and alternate cladding concepts. To compare the required fuel alterations against standard UO2/Zircaloy fuel, a 2D lattice-physics based reactivity equivalence method was established to estimate excess reactivity at the completion of each weighted batch cycle. In the case of FCM fuel, the uranium-based tristructural isotropic (TRISO) kernel and the surrounding particle layers/matrix material were altered to increase fissile loading. To match the lifetime of an 18-month pressurized water reactor (PWR) cycle, the FCM particle fuel design required roughly 10% additional fissile material at beginning of life (BOL) compared with that of a standard UO2 rod. When investigating alternate cladding concepts, cladding walls were thinned with the outer diameter unchanged, so the pellet volume and enrichment of UO2 fuel were increased. In the PWR study, a cladding thickness of 350 μm [micrometer] was simulated. Austenitic stainless steels required an increase of about 0.5 wt % enrichment to match fuel cycle requirements, while the required increase in enrichment for FeCrAl was about 0.1%. Due to the presence of the channel box, the boiling water reactor (BWR) ATF designs required additional fissile material. With the FeCrAl cladding and channel box thicknesses halved, it was estimated that an average enrichment increase of 0.6% would be required. Verification of the 2D reactivity results was performed with a 3D full-core parametric study of a representative BWR demonstrating the applicability of the 2D reactivity equivalence method for the cases herein studied. A LWR optimization code (LWROpt) was used to determine loading (LP) and control blade (CB) patterns for the ATF BWR concepts, so to help regain thermal and reactivity margins. Fuel performance was investigated with the BISON-CASL code using linear heat rate data from the optimized full-core results. The analysis demonstrated that varying power histories between FeCrAl and Zircaloy cladding greatly affect thermal expansion and centerline temperatures of the fuel rods.
Subjects/Keywords Accient Tolerant Fuel; Nuclear; Neutronics; Light Water Reactor; Optimization; Nuclear Engineering
Country of Publication us
Format application/pdf
Record ID oai:trace.tennessee.edu:utk_graddiss-4746
Repository utk-diss
Date Retrieved
Date Indexed 2019-01-07

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…End of cycle End of life Fully ceramic micro-encapsulated General Electric Co. Graphical user interface Giga-watt day Homogeneous equilibrium mixture Inner diameter Kernel diameter Low-enriched uranium Loading pattern Light water reactor Light Water

…MW MWd NIST NITE OD OF ORNL PCI PF PV PWR RPF RPT TIP TRISO Accident tolerant fuel Buffer layer Beginning of cycle Beginning of life Boiling water reactor CASMO to NESTLE Control blade Drift flux model Double heterogeneous Effective full power day…

…function Oak Ridge National Laboratory Pellet cladding interaction Packing fraction Pressure vessel Pressurized water reactor Relative power fraction Reactivity physical transformation Traversing in-core probe Tristructural isotropic x I. INTRODUCTION…

…Cladding in Light Water Reactors The United States has produced clean nuclear energy since the first power plant went critical in Shippingport, PA in 1957 [4]. Shippingport and nearly all other commercial plants that have operated in the US since…

light water cooled nuclear fuel. Regardless, SiC/SiC composites (SiC fibers embedded in SiC matrix) have gained commercial interest in hightemperature, hostile environments [23]. Material data suggests that the SiC displays excellent…

Reactor Optimization Middle of cycle Middle of life Moderator temperature coefficient Metric ton of uranium Mega-watt Mega-watt day National Institute of Standards and Technology Non-infiltration and transient eutectic-phase Outer diameter Objective…

…reacts with steam to produce free hydrogen at a much slower rate than Zircaloy. Use of these cladding materials would have mitigated hydrogen production during the accident at Fukushima Daiichi and may have prevented the explosions that ruined the reactor

…candidate for the channel box. Therefore a side study was performed with FeCrAl cladding in combination with a SiC channel box. To improve the resistance to water corrosion, the SiC was layered with Ni and Cr. In order to check the validity of each design on…

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