A tightly coupled scheme for neutronics and thermal-hydraulics using open-source software

Hsingtzu Wu, Rizwan-Uddin

Research output: Contribution to journalArticlepeer-review


Coupling neutronic and thermal-hydraulic analyses of a nuclear reactor core is important because it helps identify the most relevant safety issues without conservative assumptions. Currently coupled computations solve the same governing equations using different coupling methods, which can be sorted into two categories: loose coupling and tight coupling. This paper proposes and verifies a third coupling 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 the energy-group function. 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. The ITC method is verified using a 1.5-D (1-D neutronics and 2-D thermal-hydraulics) symmetric unit cell example. The mesh of the tightly integrated computation is 25% coarser than the loosely coupled one. Starting from a similar initial guess, the number of iterations for the ITC method is 24% fewer than that for the loosely coupled computation to reach the same accuracy. 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 ITC method has the potential to be incorporated with other neutronics and thermal-hydraulics codes.

Original languageEnglish (US)
Pages (from-to)16-22
Number of pages7
JournalAnnals of Nuclear Energy
Issue numberP2
StatePublished - Jan 29 2016


  • Neutronics
  • OpenFOAM
  • Thermal-hydraulics
  • Tightly coupled analysis

ASJC Scopus subject areas

  • Nuclear Energy and Engineering


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