Axial fuel rod expansion model in nodal code DYN3D for SFR application


Axial fuel rod expansion model in nodal code DYN3D for SFR application

Nikitin, E.; Fridman, E.

The nodal diffusion code DYN3D (Grundmann et al., 2000, 2005) is under extension for Sodium cooled Fast Reactor (SFR) application. As a part of the extension new models for thermal expansion reactivity feedbacks are needed. One of these is the reactivity feedback of the axial fuel rod expansion, which is dependent on local temperatures. The difficulty in the modeling of this effect with nodal codes can be attributed to the inflexibility of the nodal mesh i.e. all nodes in a same axial layer have to be of an identical height. This restricts the modeling to a simplified case of the radially uniform axial expansion.

In this study a new model for the treatment of axial fuel rod expansions was developed and implemented in DYN3D. The idea of the model was to preserve the axial size of the nodes and to account for the axial expansion effects by manipulation of homogenized few-group cross sections (XS). In this way the rigid nodal discretization can remain unchanged, and each node can be treated separately depending on its degree of expansion. The model recombines (“mixes”) the XS for the affected nodes, depending on the contribution of the expanded materials inside of the node.

Keywords: Thermal expansion; SFR; Monte Carlo; Serpent; Nodal diffusion method; DYN3D

  • Contribution to proceedings
    PHYSOR 2016, 01.-05.05.2016, Sun Valley, ID, USA
    Proceedings of PHYSOR 2016
  • Lecture (Conference)
    PHYSOR 2016, 01.-05.05.2016, Sun Valley, ID, USA

Permalink: https://www.hzdr.de/publications/Publ-22425
Publ.-Id: 22425