Modeling Of Hydrogen And Hydride Formation In Zirconium Alloy Cladding Using High-fidelity Multi-physics Coupled Codes

Open Access
Mankosa, Michael Garan
Graduate Program:
Nuclear Engineering
Master of Science
Document Type:
Master Thesis
Date of Defense:
Committee Members:
  • Maria Nikolova Avramova, Thesis Advisor
  • Hydrogen
  • Hydride
  • Multi-Physics
  • CTF
  • Tiamat
The reactor environment, in which nuclear fuel operates, requires improved multi-dimensional fuel and cladding simulation and analysis to accurately describe fuel behavior. The high-fidelity fuel performance code BISON was developed at Idaho National Laboratory (INL) to address this need. BISON is a three-dimensional finite-element based fuel performance code. In the high temperature environment of a reactor, the zirconium in the cladding undergoes waterside corrosion, releasing hydrogen in the process. Some of this hydrogen is absorbed by the cladding. Once hydrogen is absorbed in the cladding, its distribution is extremely sensitive to temperature, stress, and concentration gradients. Hydrogen migrates down temperature and concentration gradients and at a high enough concentration, precipitates as hydrides which can embrittle the cladding. Hydrogen distribution as a hydride precipitate in cladding has been identified as a possible ersatz for validating reactor simulation code temperature models. This thesis shows development efforts of using high-fidelity multi-physics codes to model temperature, hydrogen, and hydride distribution. Several multi-physics code couplings were used to model pressurized water reactor sub-assemblies. The first was the Penn State University (PSU) developed DeCART-CTF coupling. This thesis outlines a demonstration of this coupling’s ability to predict hydrogen distribution in the two dimensional radial (r, θ) direction. The Consortium for the Advanced Simulation of Light Water Reactors coupled multi-physics code, Tiamat, was used to model a select sub-assembly with spacer grids. A section of a single fuel pin was then selected from this sub-assembly and modeled in a three-dimensional BISON problem to obtain three-dimensional hydrogen and hydride distributions at selected areas around spacer grids. The hydrogen and hydride model showed results and behavior that accurately produced the expected physics of hydrogen and hydrides in all three dimensions. The hydrogen model is under continuing development at PSU and INL. This thesis also presents a code-to-code comparison between CTF, BISON, and FRAPCON to compare the ability of CTF to predict fuel pin temperatures. The evaluations between the codes show good agreement on fuel pin temperature distribution. If CTF is well informed by BISON or FRAPCON with gap conductance, burnup, and radial power profile values, then CTF will accurately reproduce fuel temperatures. The largest difference reported in fuel centerline temperature between CTF and FRAPCON was 6.78 degrees Kelvin or 0.49%. The largest centerline difference between CTF and BISON was 4.39 degrees Kelvin or 0.30%.