Tightly coupled neutronics and thermal-hydraulics using open-source software

Coupling the neutronic and thermal-hydraulic analyses of a nuclear reactor core is important because it helps identify the most relevant safety issues. Currently all coupled computations solve the same set of governing equations using different coupling methods, which can be sorted into two categories: loose coupling and tight coupling. This dissertation proposes and verifies a third coupled approach called “the Integrated Tight Coupling (ITC) method”. The mathematical equations in the nuclear fuel are rearranged to be integrated via a novel concept of group temperature. In addition, the data from the neutron cross section library can be used directly. The ITC method is implemented using two open-source codes: the DRAGON code and OpenFOAM. Additionally, a coupled computation using these two codes is new and has not been done in the past. The ITC method is verified using two 1.5-D (1-D neutronics and 2-D thermal-hydraulics) examples: a symmetric unit cell and an asymmetric unit cell. The mesh of the tightly integrated computation is 25 % and 12 % coarser than the loosely coupled one for the symmetric case and the asymmetric case, respectively. Starting from the similar initial guess, the number of iterations for the ITC method is 24 % and 14 % fewer than those for the loosely coupled computation to reach the same accuracy for the symmetric case and the asymmetric case, respectively. In addition, the ITC method is tested with different initial guesses. For all cases tested, the scheme converged to the same solution. With further improvement and additional testing, the scheme developed and tested here has the potential to be incorporated with other neutronics and thermal- hydraulics codes.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Nuclear Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Wu, Hsingtzu

Contributors dc:contributor

• Uddin, Rizwan
• Jewett, Brian F.
• Kozlowski, Tomasz
• Stubbins, James F.

• coupling neutronics
• tight coupling
• thermal-hydraulics

Statement dc:rights

• Copyright 2013 Hsingtzu Wu

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/46658

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/46658