Internal neutronics-temperature coupling in Serpent 2

This paper describes the built-in calculation routines in the reactor physics code Serpent 2 that provide a novel method for solving the coupled problem of the power distribution, temperature distribution, and material property distributions in nuclear fuel elements. All of the coupled distributions are solved during a single simulation with no coupling to external codes. The temperature feedback system consists of three separate built-in parts: an explicit treatment of the thermal motion of target nuclides during the transport calculation, an internal analytic radial temperature profile solver, and internal material property correlations. The internal structure and couplings of the calculation routines are described in detail, after which the results of an assembly-level problem are presented to demonstrate the capabilities and functionality of the system.