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Innovative cladding materials for advanced accident-tolerant energy systems

Periodic Reporting for period 1 - IL TROVATORE (Innovative cladding materials for advanced accident-tolerant energy systems)

Reporting period: 2017-10-01 to 2019-03-31

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 light water reactors (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 when compared to standard fuel clads (zircaloys), thus helping to take 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: select composite concepts made by different processing routes, variable microstructures & performances (mid-term technology).
2. Coated clads: protective coatings deposited on zircaloy substrates; candidate coating materials: (a) nanolaminated ternary carbides (MAX phases), and (b) nanocrystalline oxides (simple/doped) (near-term technology).
3. GESA surface-alloyed clads: the surface modification of commercial clads aims at the in-service formation of protective oxide scales. The GESA process modifies the surface of commercial clads by means of an intense pulsed electron beam; the depth of all modifications is limited, thus not affecting the bulk clad properties (near-term technology).
4. Oxide-dispersed-strengthened (ODS) iron-chromium-aluminum (FeCrAl) alloy clads: these clads 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 and 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) that combines academic excellence with industrial support, involving standardization bodies and nuclear safety regulatory authorities to accelerate the transfer of 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 were deposited by various methods (RWTH, LiU, IIT) on zircaloy-4 (Zry-4) & DIN 1.4970 stainless steel substrates; MAX phase-coated Zry-4 with bilayer diffusion barriers (RWTH, GTT); development of candidate FeCrAl alloys (KIT) for GESA surface modification of zircaloys
WP3: selection of SiC/SiC joining materials & technologies (pressureless sintering – POLITO, laser-supported joining – TUD); supply of 3 batches of joining & joined SiC materials (POLITO) for testing in WP5 and µXCT in WP4; weld qualification for 2 zircaloy grades (Zry-4 & M5) in a static autoclave
WP4: advanced materials characterization activities: (a) compression tests on pristine & ion-irradiated MAX phase micropillars made by FIB (UCAM); (b) µXCT measurements on SiC/SiC composites & glass-ceramic-joined SiC (UOXF); (c) high-resolution TEM, STEM, and EELS on pristine & ion-irradiated MAX phases (LiU)
WP5: material screening tests: (a) aqueous corrosion (330C, 10-24 days) in static PARR autoclave & CORTELINI loop (SCK•CEN); (b) steam oxidation (1200C, 1 h) (KIT)
WP6: material scoping in-situ ion irradiations (UoH) & PIE by HRTEM, STEM, EELS (LiU); PIE of proton-irradiated MAX phases (UoM, UP, etc.)
WP7: re-design of MISTRAL irradiation rig to accept ATF clad rodlets; safety file for open clad tubes passed CEE1 stage (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, etc.)
WP10: ATF clad requirements (WH SE); standardization roadmap (AFNOR); priority test methods for SiC/SiC clads (CEA)
WP11: industrial involvement: review of material screening criteria; practical/economic viability of candidate materials & processes; selection of testing requirements for various applications (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); open access publishing (all); etc.
WP13: management of R&D activities; timely submission of deliverables & milestone reports; website; fruitful collaborations with academia & industries outside Consortium; etc. (SCK•CEN)
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 future-generation (Gen-IV) nuclear systems, as confirmed by the awarded EERA JPNM label, as well as non-nuclear sectors (aerospace, concentrated solar power).
If IL TROVATORE succeeds in achieving its S&T objectives, it will help addressing the global need for safer nuclear energy, helping 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 impacts. 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 skills and competences needed for the future exploitation of the project results;
• H2020 Open Research Data Pilot: participation to maximize the open access and re-use of the project data;
• Open access to scientific publications: “green” or “gold” open access publications on project data are invariably 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; examples are 2 new test standards for SiC/SiC composites: (a) ISO 20 323 (published in March 2018), and (b) ISO/DIS 21 917 (approved at DIS stage, publication expected in 2019);
• New patents: the foreground IP in the project is expected to yield new patents that will protect the commercial exploitability of the ATF cladding materials studied in the project.
Example of R&D approach on an ATF cladding material concept studied in IL TROVATORE