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Innovative cladding materials for advanced accident-tolerant energy systems

Periodic Reporting for period 2 - IL TROVATORE (Innovative cladding materials for advanced accident-tolerant energy systems)

Reporting period: 2019-04-01 to 2020-09-30

The 2011 Fukushima Daichii event demonstrated the need for safer nuclear energy, which can be achieved by developing accident-tolerant fuels (ATFs). ATFs are expected to overcome the technical shortcomings of the standard zircaloy/UO2 fuels, thus relieving the industry from the financial penalty associated with severe accidents causing fuel cladding failure and release of radioactive fission products to the power plant containment & environment.
The main IL TROVATORE objective is to identify promising candidate ATF cladding materials for use in Gen-II/III LWRs and validate them in industrially-relevant conditions, i.e. via neutron irradiation in PWR-like water. The innovative ATF clads should demonstrate significant improvement in performance compared to standard fuel clads (zircaloys), thus taking a step towards safer nuclear energy worldwide. ATF clads must outperform commercial zircaloy clads by satisfying two requirements: (a) achieve a step enhancement in performance during nominal operation conditions & short-lived design-basis transients (<1200C), and (b) maintain hermeticity for prolonged periods during beyond-design-basis accidents (>1200C).
The ATF cladding material concepts studied in the project are:
1. SiC/SiC composite clads: various processing routes, microstructures & performances (mid-term technology).
2. Coated clads: protective coatings on zircaloy substrates; innovative coatings: (a) MAX phases, and (b) doped oxides; industrial coating: chromium (Cr) (near-term technology).
3. GESA surface-alloyed clads: the surface modification of clads aims at the in-service formation of protective oxide scales. The GESA process modifies the surface of clads by means of an intense pulsed electron beam; the depth of the modification is limited, thus not affecting the bulk clad properties (near-term technology).
4. Oxide-dispersed-strengthened (ODS) FeCrAl alloy clads: these alloys combine the high-T oxidation resistance of FeCrAl alloys with the resistance of ODS ferritic alloys to irradiation creep and swelling (mid-term technology).
The successful development of ATF clads will make the carbon-free nuclear energy safer, protecting society & environment; eliminate redundant safety systems in current reactor designs, improving their market profile; and strengthen the competitiveness of European industries in nuclear and non-nuclear sectors.
IL TROVATORE is an international collaboration (Europe, USA, Japan) combining academic excellence with industrial support, involving standardization bodies and nuclear safety regulatory authorities to accelerate the transfer of material innovation to market.
WP1: materials & suppliers: (a) SiC/SiC composites (CEA, KU, WH, NITE Corporation); (b) MAX phase ceramics (SHT, KU Leuven, DU, UP); (c) oxide ceramics (KU Leuven); (d) ODS-FeCrAl alloys (CEA, NFD)
WP2: MAX phase & oxide coatings deposited by various methods (RWTH, LiU, IIT, HSU) on zircaloy-4 (Zry-4) & DIN 1.4970 stainless steels; development of FeCrAl alloys (KIT) for zircaloy surface modification; new oxide barrier layer for Cr-coated zircaloys (IIT)
WP3: selection of SiC/SiC joining technologies (pressureless sintering – POLITO, laser-supported joining – TUD); supply of joining materials & joined SiC/SiC materials (POLITO) for characterization; weld qualification for 2 zircaloy grades (Zry-4 & M5) in static autoclave
WP4: advanced materials characterization activities: compression tests on pristine & ion-irradiated MAX phase micropillars made by FIB (UCAM); µXCT measurements on SiC/SiC composites & joints (UOXF); (c) HRTEM/STEM/EELS on pristine, ion-irradiated & indented MAX phases (LiU); etc.
WP5: material screening tests: (a) aqueous corrosion (330C, 10-30 days) in static PARR autoclave & CORTELINI loop (SCK•CEN); (b) high-T steam oxidation (1200C, 1 h) & transient steam oxidation tests up to 1820C (KIT)
WP6: material scoping in-situ ion irradiations (UoH) & PIE by HRTEM/STEM/EELS (LiU); proton irradiation of bulk materials (MAX phases, SiC/SiC composites, etc.) & strain mapping by HRDIC to assess radiation effects
WP7: design of MISTRAL-N irradiation rig for sealed ATF clad rodlets; safety file for ATF rodlets & MISTRAL requalified basket & WATCH water chemistry unit: in final CEE3 stage (SCK•CEN); loading 3 needles of MISTRAL-N with ATF rodlets (Cr-coated zircaloy, SiC/SiC composites) for cycles 1-3 of BR2 irradiation (SCK•CEN)
WP8: mining of existing ion/proton/neutron irradiation data (SCK•CEN)
WP9: various predictive modelling activities (MD, DFT, KMC, thermodynamic, etc.) (SCK•CEN, GTT, KTH, UOXF, etc.)
WP10: ATF clad requirements (WH SE); standardization roadmap (AFNOR); priority test methods for SiC/SiC composite clads (CEA); development of high-T testing capabilities (DLR)
WP11: industrial involvement: review of material screening criteria; practical/economic viability of candidate materials & processes; etc. (WH, EDF)
WP12: communication action plan, data management plan, plan for exploitation & dissemination of results (SCK•CEN); Workshop on MAX phases for harsh environments (UP); Workshop on surface engineering technologies (KIT); Workshop on multiscale modelling (virtual); open access publishing (all); etc.
WP13: management of R&D activities; website; collaborations with academia & industries outside Consortium; delays in submission of deliverables & milestone reports in 2nd reporting period due to COVID-19 pandemic; transfer of project coordination from SCK•CEN to UoH; etc.
The main project ambition is to be a stepping stone in the global quest for improved nuclear energy safety by delivering proof-of-concept ATF clads. This makes IL TROVATORE important for the Gen-II/III LWR community, as confirmed by the awarded NUGENIA label. Moreover, the cross-cutting character of its R&D activities is expected to benefit Gen-IV nuclear systems, as confirmed by the awarded EERA JPNM label, as well as non-nuclear sectors (aerospace, CSP).
If IL TROVATORE succeeds in achieving its S&T objectives, it will help addressing the global need for safer nuclear energy, aiding industrial stakeholders to bring the achieved innovation to market. This is in response to the amended Nuclear Safety Directive, which highlights the need for high nuclear safety standards in the EU and encourages cooperation on nuclear safety issues with global impact. The anticipated financial impacts of the commercialization of the innovative ATF clads studied in IL TROVATORE are enormous, not only due to the introduction of new materials in NPPs, but also due to the elimination of redundant safety systems, the prolongation of the lifetime of the current fleet of NPPs, etc.
Additional IL TROVATORE impacts involve:
• Education & training (E&T): organization of various E&T activities that aim at developing competences needed for the future exploitation of project results;
• H2020 Open Research Data Pilot: maximization of open access and re-use of the project data;
• Open access to scientific publications: “green” or “gold” open access publications on project data are uploaded to the Zenodo online repository;
• New standards: new standards (specifications, test standards) will expedite the qualification & licensing process for the innovative ATF clads studied in the project;
• New patents: the foreground IP in the project is expected to yield new patents that will protect the commercial exploitability of the innovative ATF cladding materials.
Approach for performance optimisation of SiC/SiC composite ATF cladding materials