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Uppsala University

1.
Westlund, Marcus.
Monte Carlo Simulations of *Bowing* Effects Using Realistic *Fuel* Data in Nuclear *Fuel* Assemblies.

Degree: Applied Nuclear Physics, 2019, Uppsala University

URL: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-377279

Deformations of nuclear fuel assemblies have been observed in nuclear power plants since the mid-90s. Such deformations are generally called bowing effects. Fuel assemblies under high irradiation undergo growth and creep induced by high loading forces and low skeleton stiffness of the assemblies which gives permanent deformations and modifies moderation regions. Hence, giving an unpredicted neutron flux spectrum, power distribution, and isotopic concentrations in the burnt fuel. The aim of this thesis is to study the effects of local fuel bowing in terms of power distribution and isotopic composition changes through simulations of the reactor core. The reactor is simulated with realistic bowing maps and previous deterministically simulated realistic fuel data from a present reactor by deploying the Monte Carlo method using the nuclear reactor code Serpent 2. Two subparts of a full reactor core with fuel from separate fuel cycles are investigated in 2D using burnup. To quantify the impact of the bowing, the change in power distribution and the induced isotopic composition change are calculated by a relative difference between a nominal case and a simulation with perturbed fuel assemblies. The results are presented in colormaps, for visualization. The isotopic composition for U235, U238, Pu239, Nd148, and Cm244 are investigated. Also, statistical uncertainty estimations in the composition of the depleted fuel are done by multiple calculations of the same geometry while changing the seed of random variables in the Monte Carlo calculation. The mean value and the standard deviation in the mass density of U235 and Pu239 are calculated for two pins together with histograms with a normal fit for each case to clarify the mathematical distribution of the calculations. The simulations performed in this thesis have detected clear impacts of the reactor behavior in terms of power distribution and isotopic composition in the burnt fuel introduced by the bowing. Assembly perturbations of about 10 mm may locally introduce a 10 % relative difference in power density and U235 content between the nominal and the bowed case at 15 MWd/kgU burnup. The power and the isotopic composition changes agree with expectations from the bowing maps.

Subjects/Keywords: bowing effects; fuel assembly perturbations; nuclear; serpent; monte carlo; Atom and Molecular Physics and Optics; Atom- och molekylfysik och optik

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^{th} Edition):

Westlund, M. (2019). Monte Carlo Simulations of Bowing Effects Using Realistic Fuel Data in Nuclear Fuel Assemblies. (Thesis). Uppsala University. Retrieved from http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-377279

Note: this citation may be lacking information needed for this citation format:

Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^{th} Edition):

Westlund, Marcus. “Monte Carlo Simulations of Bowing Effects Using Realistic Fuel Data in Nuclear Fuel Assemblies.” 2019. Thesis, Uppsala University. Accessed March 24, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-377279.

Note: this citation may be lacking information needed for this citation format:

Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^{th} Edition):

Westlund, Marcus. “Monte Carlo Simulations of Bowing Effects Using Realistic Fuel Data in Nuclear Fuel Assemblies.” 2019. Web. 24 Mar 2019.

Vancouver:

Westlund M. Monte Carlo Simulations of Bowing Effects Using Realistic Fuel Data in Nuclear Fuel Assemblies. [Internet] [Thesis]. Uppsala University; 2019. [cited 2019 Mar 24]. Available from: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-377279.

Note: this citation may be lacking information needed for this citation format:

Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Westlund M. Monte Carlo Simulations of Bowing Effects Using Realistic Fuel Data in Nuclear Fuel Assemblies. [Thesis]. Uppsala University; 2019. Available from: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-377279

Not specified: Masters Thesis or Doctoral Dissertation

2.
Bopp, Andrew T.
The calculation of *fuel* *bowing* reactivity coefficients in a subcritical advanced burner reactor.

Degree: MS, Mechanical Engineering, 2013, Georgia Tech

URL: http://hdl.handle.net/1853/50295

The United States' fleet of Light Water Reactors (LWRs) produces a large amount of spent fuel
each year; all of which is presently intended to be stored in a fuel repository for disposal. As these
LWRs continue to operate and more are built to match the increasing demand for electricity, the
required capacity for these repositories grows. Georgia Tech's Subcritical Advanced Burner Reactor
(SABR) has been designed to reduce the capacity requirements for these repositories and thereby
help close the back end of the nuclear fuel cycle by burning the long-lived transuranics in spent nuclear
fuel. SABR's design is based heavily off of the Integral Fast Reactor (IFR).
It is important to understand whether the SABR design retains the passive safety characteristics
of the IFR. A full safety analysis of SABR's transient response to various possible accident scenarios
needs to be performed to determine this. However, before this safety analysis can be performed, it is
imperative to model all components of the reactivity feedback mechanism in SABR. The purpose of
this work is to develop a calculational model for the fuel bowing reactivity coefficients that can be used
in SABR's future safety analysis. This thesis discusses background on fuel bowing and other reactivity
coefficients, the history of the IFR, the design of SABR, describes the method that was developed for
calculating fuel bowing reactivity coefficients and its validation, and presents an example of a fuel
bowing reactivity calculation for SABR.
*Advisors/Committee Members: Stacey, Weston M. (advisor), Petrovic, Bojan (committee member), Ghiaasiaan, Mostafa (committee member), Grudzinski, Jim (committee member).*

Subjects/Keywords: SABR; Reactivity; Fuel bowing; Nuclear reactors; Light water reactors; Spent reactor fuels; Fast reactors

…and design-specific reactivity feedback is *fuel* *bowing*. *Fuel* *bowing* occurs
when one side of… …designed to restrict any
*fuel* *bowing* in the pins themselves, so non-uniform temperatures across… …the *fuel* assemblies are the
main driver for *fuel* *bowing*.[4] In other words, *fuel*… …This means that the behavior of *fuel* *bowing* feedbacks is highly
design-specific and in… …Reactivity feedback due to *fuel* *bowing* was first noticed in Argonne National Laboratory's…

Record Details Similar Records

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^{th} Edition):

Bopp, A. T. (2013). The calculation of fuel bowing reactivity coefficients in a subcritical advanced burner reactor. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/50295

Chicago Manual of Style (16^{th} Edition):

Bopp, Andrew T. “The calculation of fuel bowing reactivity coefficients in a subcritical advanced burner reactor.” 2013. Masters Thesis, Georgia Tech. Accessed March 24, 2019. http://hdl.handle.net/1853/50295.

MLA Handbook (7^{th} Edition):

Bopp, Andrew T. “The calculation of fuel bowing reactivity coefficients in a subcritical advanced burner reactor.” 2013. Web. 24 Mar 2019.

Vancouver:

Bopp AT. The calculation of fuel bowing reactivity coefficients in a subcritical advanced burner reactor. [Internet] [Masters thesis]. Georgia Tech; 2013. [cited 2019 Mar 24]. Available from: http://hdl.handle.net/1853/50295.

Council of Science Editors:

Bopp AT. The calculation of fuel bowing reactivity coefficients in a subcritical advanced burner reactor. [Masters Thesis]. Georgia Tech; 2013. Available from: http://hdl.handle.net/1853/50295