Azimuthal Hydrogen Concentration Factor using the Bison Fuel Performance Code

Open Access
Piotrowski, Christopher Joseph
Graduate Program:
Nuclear Engineering
Master of Science
Document Type:
Master Thesis
Date of Defense:
Committee Members:
  • Arthur Thompson Motta, Thesis Advisor
  • Azimuthal Hydrogen Concentration
  • hydride
Hydrogen can enter nuclear reactors because of the corrosion reaction. Hydrogen that is picked up by nuclear reactor cladding may become heterogeneously distributed due to concentration gradients as described by Fick’s law and temperature gradients as described by the Soret effect. Understanding hydrogen behavior is important for ensuring the safety and integrity of a nuclear reactor, since hydrogen that precipitates as hydrides may weaken cladding and lower ductility. This phenomenon has been studied by many researchers since the start of the nuclear industry. In order to predict hydrogen and hydride distributions, computer codes are essential because of the complexity of models and reactor conditions. A hydrogen transport and precipitation model was created and simulations were previously conducted that predicted the radial and axial distributions of hydrogen and hydrides under various conditions. The current objective of this study and goal of this project is to simulate various azimuthally dependent hydrogen and hydride distributions. This is done through the use of BISON fuel performance that is indirectly coupled to Penn State maintained thermal-hydraulics code, COBRA-TF and the neutronics code, Deterministic Core Analysis based on Ray Tracing (DeCART). The goal of the azimuthal simulations is to produce boundary condition in which hydrogen and hydride distributions are most heterogeneous. The three simulations highlighted in this study include modeling a 4x4 pin array where a water rod is located near the rod of interest to produce a large thermal gradient, a partially inserted control rod located near the rod of interest to produce a thermal gradient based on differences in power, and modeling cladding in which a portion of the oxide has broken off producing a thermal gradient in the spalled region. A new azimuthal mesh and associated boundaries was created in order to simulate these scenarios. The water rod and control rod simulations used COBRA-TF and DeCART outputs as boundary conditions for the BISON input deck. In each of the simulations, the hydrogen in solid solution diffused to the colder regions, as anticipated, leading to hydride precipitation in specific favored regions. This resulted in a high concentration in hydride which we believe mimics real cases. Further work can be done to add more competing driving forces to the BISON fuel performance code such as the effect of applied stress on hydrogen and hydride distributions.