NSUF 21-4255: Radiation-induced Crystallization in Alumina Coatings: Temperature and Yttria Doping Effect. A Completion Kinetic Study to Model Radiation Resistant Coatings for the Future Nuclear System.
Different fission reactor concepts have been proposed as Generation IV candidates. Among all, Lead-cooled Fast Reactors (LFRs) are particularly interesting. LFR technology also eliminates the need and associated expense of extra components and redundant safety systems required by other plant designs for protection against coolant leakages. Moreover, the fast neutron spectrum operation facilitates improved uranium resource utilization and reduced nuclear waste generation, with the potential to close the nuclear fuel cycle. In the increasing efficiency vision, industrial companies, such as Westinghouse, aim to increase the operating temperature up to 800 °C.
However, at projected operating temperatures, typical corrosion rates in these systems are not acceptable, and protective methods are required. In this framework, one of the most interesting solutions is to use coatings as an anti-corrosion barrier. For this respect, the Istituto Italiano di Tecnologia (IIT) research studied an amorphous/nanocrystalline Al2O3 coating produced by Pulsed Laser Deposition (PLD) for liquid metal-cooled nuclear systems. The studies confirmed that the PLD-grown Al2O3 is a suitable candidate for protecting steels in lead and Pb-alloys at temperatures up to 600°C. The material response under irradiation has been studied with various heavy ions irradiation. The main feature behind these promising pieces of evidence has been identified in the amorphous/nanocrystalline structure of alumina films, which confers a unique assemble of strong adhesion, metal-like mechanical properties radiation-tolerance. Several studies have investigated alumina properties, but few are dedicated to the crystallization in PLD-alumina, and the exact evolution and the precise transformations within the system are still unknown. This is why further studies are needed to evaluate the amorphous to crystalline transition, also under irradiation.
In December 2018 and in August 2020, two different experimental campaigns were carried out at the IVEM-tandem facility. Experiments on pure alumina and (3%) Yttria doped alumina were carried out. A preliminary kinetic study has been performed. It was evident that a power-function relationship exists between the minimum DPA needed for starting crystallization and temperature. If these results will be confirmed, decreasing further temperature means that higher and higher DPA values ( or ion fluence) are needed to induce crystallization in alumina. Potentially, an almost infinite DPA value (10^11 DPA) is needed to induce crystallization at room temperature.
Regarding doping effects, Yttria effectively deters the radiation-induced crystallization in the system and the average grain dimensions were smaller than that in the pure alumina. Some preliminary analysis has been carried out for the doped alumina. However, the data is still needed for the lower temperatures (400ºC and 500ºC), so the trend of doping effect on the kinetic evolution could be confirmed. Moreover, the effect of increasing the doping concentration in the system is still unknown. It would be interesting to understand if a delay effect proportional to the doping concentration is detectable.
This project represents a continuation of the work started, at the IVEM facility. New concentrations of dopant will be compared. Tests will be focused to complete the picture already obtained to assess the feasibility of Al2O3-based coatings for high-temperature nuclear power plants.
Additional Info
| Field | Value |
|---|---|
| Abstract | Different fission reactor concepts have been proposed as Generation IV candidates. Among all, Lead-cooled Fast Reactors (LFRs) are particularly interesting. LFR technology also eliminates the need and associated expense of extra components and redundant safety systems required by other plant designs for protection against coolant leakages. Moreover, the fast neutron spectrum operation facilitates improved uranium resource utilization and reduced nuclear waste generation, with the potential to close the nuclear fuel cycle. In the increasing efficiency vision, industrial companies, such as Westinghouse, aim to increase the operating temperature up to 800 °C. However, at projected operating temperatures, typical corrosion rates in these systems are not acceptable, and protective methods are required. In this framework, one of the most interesting solutions is to use coatings as an anti-corrosion barrier. For this respect, the Istituto Italiano di Tecnologia (IIT) research studied an amorphous/nanocrystalline Al2O3 coating produced by Pulsed Laser Deposition (PLD) for liquid metal-cooled nuclear systems. The studies confirmed that the PLD-grown Al2O3 is a suitable candidate for protecting steels in lead and Pb-alloys at temperatures up to 600°C. The material response under irradiation has been studied with various heavy ions irradiation. The main feature behind these promising pieces of evidence has been identified in the amorphous/nanocrystalline structure of alumina films, which confers a unique assemble of strong adhesion, metal-like mechanical properties radiation-tolerance. Several studies have investigated alumina properties, but few are dedicated to the crystallization in PLD-alumina, and the exact evolution and the precise transformations within the system are still unknown. This is why further studies are needed to evaluate the amorphous to crystalline transition, also under irradiation. In December 2018 and in August 2020, two different experimental campaigns were carried out at the IVEM-tandem facility. Experiments on pure alumina and (3%) Yttria doped alumina were carried out. A preliminary kinetic study has been performed. It was evident that a power-function relationship exists between the minimum DPA needed for starting crystallization and temperature. If these results will be confirmed, decreasing further temperature means that higher and higher DPA values ( or ion fluence) are needed to induce crystallization in alumina. Potentially, an almost infinite DPA value (10^11 DPA) is needed to induce crystallization at room temperature. Regarding doping effects, Yttria effectively deters the radiation-induced crystallization in the system and the average grain dimensions were smaller than that in the pure alumina. Some preliminary analysis has been carried out for the doped alumina. However, the data is still needed for the lower temperatures (400ºC and 500ºC), so the trend of doping effect on the kinetic evolution could be confirmed. Moreover, the effect of increasing the doping concentration in the system is still unknown. It would be interesting to understand if a delay effect proportional to the doping concentration is detectable. This project represents a continuation of the work started, at the IVEM facility. New concentrations of dopant will be compared. Tests will be focused to complete the picture already obtained to assess the feasibility of Al2O3-based coatings for high-temperature nuclear power plants. |
| Award Announced Date | 2021-06-07T16:18:08.46 |
| Awarded Institution | Idaho National Laboratory |
| Facility | Advanced Test Reactor |
| Facility Tech Lead | Alina Zackrone, Wei-Ying Chen |
| Irradiation Facility | None |
| PI | Fabio Di Fonzo |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 4255 |