Aaron Colldeweih

• PhD Student - École polytechnique fédérale de Lausanne / PSI

• Project Title: Effects of Hydrogen Concentration, Temperature, and Irradiation Damage on Delayed Hydride Cracking in Zircaloy-2

• Working across Key Challenge 2, Key Challenge 3, and Key Challenge 4.

Aaron Colldeweih completed a BSc in Mechanical Engineering at the University of California, Davis followed by an MSs in Nuclear engineering at the Eidgenössische Technische Hochschule Zürich. Aaron is conducting his research at the Paul Scherrer Institut (PSI) in Switzerland. The project is funded by swissnuclear and Nagra.

Aaron’s project will focus on investigating the influence of hydrogen content, temperature, and irradiation damage on delayed hydride cracking (DHC) in Zircaloy-2. The novelty of the investigations lie within the testing methods, which directly examines fuel cladding material in order to gain a geometrical perspective of the phenomenon and respective variables. Additionally, high-resolution neutron radiography is performed at the Swiss neutron spallation source (SINQ) located at PSI to image DHC samples providing qualitative and quantitative insight into the hydrogen diffusion and precipitation during cracking. The findings will be used to advise fuel handling during transport and dry storage as well as fuel performance models that predict the kinetics of hydrogen in Zr alloys.

Next Steps: Having competed his PhD, Aaron has taken a position at Idaho National Laboratory, where his role focuses on post-irradiation examination (PIE) of Reactor Structural Materials. Some of Aaron’s PhD findings are covered in his recent Materialia paper on Zirconium hydride phase mapping in Zircaloy-2 cladding after delayed hydride cracking.