2026-09-20T23:00:04Zhttps://dspace.mit.edu/server/oai/requestoai:dspace.mit.edu:1721.1/1273052021-07-05T14:03:20Zcom_1721.1_7582com_1721.1_7581col_1721.1_131023
Lin-Wen Hu.
Allen, Dakota J.
Massachusetts Institute of Technology. Department of Nuclear Science and Engineering.
Massachusetts Institute of Technology. Department of Nuclear Science and Engineering
2020-09-15T21:51:18Z
2020-09-15T21:51:18Z
2020
2020
https://hdl.handle.net/1721.1/127305
1191903772
Thesis: S.M., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2020
Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 107-109).
In the framework of non-proliferation policy, the Massachusetts Institute of Technology Reactor (MITR) is planning to convert from highly enriched uranium (HEU) to low enriched uranium (LEU) fuel. A new type of high-density LEU fuel based on a monolithic U-10Mo alloy is being qualified to allow the conversion of all remaining U.S. high performance research reactors including the MITR. The purpose of this study is to understand the impact of proposed MITR LEU "FYT" fuel element fabrication tolerances on the operation and safety limits of the MITR. Therefore, the effects of fabrication specification parameters on all levels of the core, ranging from full-core alterations to individual spots on the fuel plates were analyzed. Evaluations at the design tolerances, and beyond, were conducted through neutronics and thermal hydraulics calculations.
The first step was analyzing the separate effects that parameters, including enrichment, fuel mass loading, fuel plate thickness, and impurities, have on the reactor physics of the core. These analyses were used to develop curve fits to predict the effect of these parameters on the excess reactivity of fresh fuel inserted into the LEU core. These models could then be used to estimate the effect on fuel cycle length to ensure the tolerances would not cause significant changes to the operating cycle of MITR. These analyses estimated the margin to criticality present in the core and ensured that the reactivity shutdown margin (SDM) was not violated. Other parameters such as coolant channel gap and local fuel homogeneity cause primarily local impacts including the power distribution within the fuel element, and related impacts to thermal hydraulic margins.
This modeling was necessary to ensure that these parameters would not cause the margin to MITR's thermal hydraulic safety limit, the onset of nucleate boiling (ONB), to be violated. The final step was a covariance analysis of the combined effects at a full-core and element level. This combined effect analysis assured that the core would maintain proper safety and operational margins with a realistic distribution of off-nominal parameters. Given the comprehensive analysis performed, the current design fabrication tolerances were determined to provide acceptable fuel cycle length and safety margins consistent with the MITR LEU preliminary safety analysis report, and a basis for updating these tolerances during planned manufacturing-scale plate fabrication demonstrations has been established.
by Dakota Allen.
S.M.
S.M. Massachusetts Institute of Technology, Department of Nuclear Science and Engineering
109 pages
eng
Massachusetts Institute of Technology
MIT theses may be protected by copyright. Please reuse MIT thesis content according to the MIT Libraries Permissions Policy, which is available through the URL provided.
http://dspace.mit.edu/handle/1721.1/7582
Nuclear Science and Engineering.
Impact assessment for the MIT Research Reactor low enrichment uranium fuel fabrication tolerances
Thesis
application/pdf
2020-09-15T21:51:18Z
Publication
Master
NucEng
unknown
unknown
<Publication xmlns="https://www.openaire.eu/cerif-profile/1.1/" id="12fb1984-bd4a-4f16-97bf-fbf39f3e4068">
<Type xmlns="https://www.openaire.eu/cerif-profile/vocab/COAR_Publication_Types">http://purl.org/coar/resource_type/c_1843</Type>
<Language>eng</Language>
<Title>Impact assessment for the MIT Research Reactor low enrichment uranium fuel fabrication tolerances</Title>
<PublishedIn>
<Publication>
</Publication>
</PublishedIn>
<PublicationDate>2020</PublicationDate>
<Authors>
<Author>
<DisplayName>Allen, Dakota J.</DisplayName>
<Affiliation>
<OrgUnit>
</OrgUnit>
</Affiliation>
</Author>
</Authors>
<Editors>
</Editors>
<Publishers>
<Publisher>
<DisplayName>Massachusetts Institute of Technology</DisplayName>
<OrgUnit />
</Publisher>
</Publishers>
<License>http://dspace.mit.edu/handle/1721.1/7582</License>
<Keyword>Nuclear Science and Engineering.</Keyword>
<Abstract>In the framework of non-proliferation policy, the Massachusetts Institute of Technology Reactor (MITR) is planning to convert from highly enriched uranium (HEU) to low enriched uranium (LEU) fuel. A new type of high-density LEU fuel based on a monolithic U-10Mo alloy is being qualified to allow the conversion of all remaining U.S. high performance research reactors including the MITR. The purpose of this study is to understand the impact of proposed MITR LEU "FYT" fuel element fabrication tolerances on the operation and safety limits of the MITR. Therefore, the effects of fabrication specification parameters on all levels of the core, ranging from full-core alterations to individual spots on the fuel plates were analyzed. Evaluations at the design tolerances, and beyond, were conducted through neutronics and thermal hydraulics calculations.</Abstract>
<Abstract>The first step was analyzing the separate effects that parameters, including enrichment, fuel mass loading, fuel plate thickness, and impurities, have on the reactor physics of the core. These analyses were used to develop curve fits to predict the effect of these parameters on the excess reactivity of fresh fuel inserted into the LEU core. These models could then be used to estimate the effect on fuel cycle length to ensure the tolerances would not cause significant changes to the operating cycle of MITR. These analyses estimated the margin to criticality present in the core and ensured that the reactivity shutdown margin (SDM) was not violated. Other parameters such as coolant channel gap and local fuel homogeneity cause primarily local impacts including the power distribution within the fuel element, and related impacts to thermal hydraulic margins.</Abstract>
<Abstract>This modeling was necessary to ensure that these parameters would not cause the margin to MITR's thermal hydraulic safety limit, the onset of nucleate boiling (ONB), to be violated. The final step was a covariance analysis of the combined effects at a full-core and element level. This combined effect analysis assured that the core would maintain proper safety and operational margins with a realistic distribution of off-nominal parameters. Given the comprehensive analysis performed, the current design fabrication tolerances were determined to provide acceptable fuel cycle length and safety margins consistent with the MITR LEU preliminary safety analysis report, and a basis for updating these tolerances during planned manufacturing-scale plate fabrication demonstrations has been established.</Abstract>
<Access xmlns="http://purl.org/coar/access_right"
>
</Access>
</Publication>