Remigijus Janulionis doctoral dissertation defense

Author, Institution: Remigijus Janulionis, Lithuanian Energy Institute

Dissertation title: Numerical Research of Fracture of Nuclear Energy Objects Construction Elements with Hydrides under Thermal Impact

Science area, field of science: Technological Sciences – Energy and Power Engineering, T006

Defense of the dissertation: 2020-06-17, 14:00, Lithuanian Energy Institute (room – AK-330 a.), Breslaujos st. 3, Kaunas, Lithuania.

Scientific Supervisor: Dr. Gintautas Dundulis (Lithuanian Energy Institute, Technological Sciences, Energetics and Power Engineering, T006)

Dissertation Defense Board of Energetics and Power Engineering Science Field:

• Chairperson – Dr. Raimondas Pabarčius (Kaunas University of Technology, Technological Sciences, Energetics and Power Engineering, T006);
• Prof. Dr. Leon Cizelj (Jozef Stefan Institute, Slovenia, Technological Sciences, Mechanical Engineering, T009)
• Prof. Dr. Habil. Rimantas Kačianauskas (Vilniaus Gediminas Technical University, Technological Sciences, Mechanical Engineering, T009);
• Prof. Dr. Habil. Gintautas Miliauskas (Kaunas University of Technology, Technological Sciences, Energetics and Power Engineering, T006);
• Dr. Egidijus Urbonavičius (Lithuanian Energy Institute, Technological Sciences – Energetics and Power Engineering, T006).

The doctoral dissertation is available on the internet and at the library of Kaunas University of Technology (K. Donelaičio st. 20, Kaunas) and the Lithuanian Energy Institute (Breslaujos st. 3, Kaunas, Lithuania).

Annotation:
Nuclear reactors fuel claddings and fuel channels are made of zirconium alloys, which, in addition to the ageing mechanisms of other metals, are also susceptive to hydrogen absorption and it following delayed hydride cracking mechanisms. Usually, the effects of the ageing of materials are evaluated by laboratory tests. As fuel claddings and fuel channels are the protective measures to prevent the release of radioactive fission products into the environment, their experimental studies are complex, difficult, and costly. Therefore, alternative methods are needed for the material ageing assessment. The aim of this research is to determine the fracture toughness of nuclear energy objects construction elements made of zirconium alloy with hydrides under thermal impact using the developed numerical method.

To achieve the aim of the research a new numerical simulation methodology has been proposed, which allows numerical determination of fracture toughness of zirconium alloys at different hydrogen concentrations. Also, the crack growth determination methods were supplemented with the proposed and validated polynomial equation. By applying this methodology for the fuel channels and fuel claddings it is possible to predict a change in their properties due to the hydrogen absorption mechanism during the operation of a reactor or the storage of spent nuclear fuel. Therefore, using this methodology, it is possible to improve the design of fuel claddings and spent fuel storage procedures.