Professor Constantina Lamblinow of Huddersfield University explains the relationship between fundamentally innovative nuclear materials and safer nuclear energy.
The Fukushima Daiichi event in March 2011 demonstrated the need for safer nuclear energy and thus became a major driver of global investment in accident-resistant fuels (ATFS). The Fukushima event was caused by melting-material failure of zirconium-based alloy (zircaloy) fuel bandages during the 2011 East Japan Earthquake and the loss of cooling accident (LOCA) after the tsunami. The cladding failure of Zircaloy fuel was caused by a runaway reaction with steam, producing steam, large amounts of heat and hydrogen, thus rapidly increasing the core temperature until meltdown, followed by hydrogen explosions and release of radioactive fission products beyond the site boundary.
Such undesired nuclear events can have harmful effects on both the society and the environment near nuclear power plants, and can discourage the widespread use of nuclear energy.
The root cause of the Fukushima event lies in the inherent drawbacks of standard Zircaloy, so the development of ATF cladding materials that can overcome these drawbacks is extremely important. Rapid deployment of ATF cladding increases the safety of the reactor by purchasing the valuable time required to deploy appropriate measures during an accident scenario and resuming reactor control. Furthermore, ATF bandages can ensure economic benefits from higher achievable levels of fuel combustion and enrichment due to slow corrosion of reactor materials during nominal operations, thus increasing the fuel cycle, reducing fuel costs and promoting the use of nuclear fuel before disposal of waste.
Scorpion Project
The Horizon Scorpion Project is an international collaboration (16 partners from the EU, UK, US, Japan and Switzerland) targeting performance optimization for the “innovative” SIC/SIC Composite ATF Cladding Material Concept. SIC/SIC composites (i.e., SIC fiber reinforced SIC matrix composites) are ideal for photowater reactor (LWR) service environments due to their excellent intolerance (i.e., SIC, high temperature stability due to high melting points of TM≈2830°C), pseudo-duality (i.e., monoliths with enhanced resistance to enhanced resistance to enhanced resistance to enhanced resistance to enhanced resistance to enhanced resistance to enhanced resistance to enhanced resistance to enhanced resistance to enhanced resistance to enhanced resistance to monoliths), and accelerated steam oxidation in the event of LOCA. It is also worth noting that the inbending and chemical compatibility of SIC/SIC composites with corrosive media (e.g. heavy liquid metals and molten salts) will become a candidate material for future produced nucleic acid reactors (LFRS), gas-cooled rate reactors (GFRS), highly bloated reactors (VHTRS (VHTRS), feltors Ructors (vhtrs), feltors reactors (lfrs), and felter reactors (lfrs), as fusion reactors.
Successful overcoming the drawbacks of certain materials is a prerequisite for the deployment of SIC/SIC composite ATF cladding materials in LWR. One such drawback is that insufficient compatibility between SIC and water (nominal operating conditions) and steam (temporary/accident conditions) was observed in two international collaboration frameworks that link directly to Scorpion and focus on innovative ATF cladding materials. (Seven partners, the EU and the US).
First, damage suffered by SIC under irradiation in contact with water (i.e., the main coolant in LWR) was detected using synergistic proton irradiation/water-based corrosion testing of CVD (chemical vapor deposition) (deposited chemical vapor) sic was exposed to slow flowing water. These tests were performed within the I-Neri Perseus project of the unique IAC (irradiated accelerated corrosion) cells, as outlined in Figure 1a. IAC Cells are available at MIBL (Ion Beam Lab, Michigan) at the University of Michigan. CVD SIC is typically used as an outer protective coating for CVI (chemical vapor infiltration) SIC/SIC composite ATF cladding. Disc-shaped CVD SIC samples (Ø3 mm, 48 μm thick) were tested with 5.4 MEV protons (P+) at 3220°C for 48 hours and PWR (pressurized water furnace) water with 3 ppm (H₂). Microstructural examination of the combined CVD SICs showed that the material was composed of high density columnar SIC particles in stacked faults (SFS) images of parallel thin lines of HAADF stems (high angle annular dark field scan transmission electron microscope).
After testing, the CVD SIC disk appears to be perforated (Fig. 1B), and three regions on its surface were identified by changes in the SIC decomposition mechanism (see inset in Fig. 1a). Further STEM analysis revealed preferential attacks of grain boundaries (GBS) and SFS by water radiolysis species such as H+ (Fig. 1D). The attacks of GBS and SFS created fresh surfaces in originally dense CVD SICs, enhancing the formation and subsequent dissolution of silica (SIO₂), the main product of SIC oxidation in water and steam. These findings are consistent with AB initio molecular dynamics simulations of the SIC aqueous corrosion effect, which showed that immobilization of Si–C bonds by hydrogen species is a critical step in the SIC hydrogen decomposition process.
Second, damage in which the SIC is in contact with the steam was observed at a test temperature above the melting point of the high-temperature SIO₂ polymorph (TM≈1723°C). MoltenSio₂ reacts with solid SICs and produces gaseous species (SIO and CO), which rapidly damages SIC/SIC composite ATF cladding in the event of a severe accident above the melting point of β-crostobalite. This was systematically confirmed within the H2020 IL Trovatore Project by very high temperature steam oxidation testing. The results of these invaluable test metrics are shown in Figure 2.
The value of a test setup that can simulate conditions within a reactor
Findings from IAC Cell and Quench SR facilities highlight the added value of clinical laboratory setups that can be replicated to some extent.
Clearly, the ultimate verification of material performance can only be provided by neutron irradiation of innovative nuclear materials in contact with nuclear system-specific coolants (such as water, liquid metals, molten salts, helium, etc.). Unfortunately, the lack of sufficiently powerful test reactors accessible after Fukushima events in Europe and the US, etc., will ensure that the performance of innovative ATF cladding materials is evaluated in a rapid effort, and presents a critical effort to make nuclear energy safer as quickly as possible. A small number of available test reactors that can rapidly accumulate radiation damage of novel materials (e.g. Belgium, HFIR, and ATR) overregister or prioritize the production of medical radioisotopes for cancer detection and treatment. Therefore, investment in new test reactors is of paramount importance to modernizing nuclear energy and supporting the future aspirations of ensuring global energy security.
Another challenge is the rarity of research facilities that are suitably equipped to perform post-irradiation (PIE) analysis of neutron irradiation materials (JRC Karlsruhe in Germany and certain US national labs). New investments in such facilities are necessary to promote the testing and qualification of innovative nuclear materials, thereby helping to increase the efficiency and safety of nuclear reactors in the near future.
SCORPION Approach SIC Performance Optimization
The Horizon Scorpion project employs two fundamentally new approaches to improve compatibility between LWR coolant (water/steam) and SIC/SIC composite ATF cladding materials.
Development of protective coatings that can prevent the formation of Sio₂ to jeopardize the reliable performance of SICs in contact with water and steam. Grain boundary (GB) engineering of SIC, which has compounds that exhibit excellent stability to water and steam.
Figure 1E shows SEM (scanning electron microscope) images of pressureless sintered ytthorium aluminum garnet (YAG) and spark plasma sintered SICs with GBS designed with YAG. Yag (y₃al₅o₁₂) is a candidate SIC coating material that is excellent in water/vapor compatible. This material has already been tested in IAC cells under identical conditions at CVD SIC, i.e. 5.4 MEV P+, 320°C, 48 hours, at 3 ppm H₂ in PWR water. Figure 1F shows that the tested YAG discs (Ø3 mm, 50 μm thick) showed overall performance, showing only mild GB etching in areas 1 and 2, and the dissolution of parasitic alumina (Al₂o₃) in areas 1-3.
reference
SS Lyman, A. Flick, O. Toader, P. Wan, Namad, Z. Jiao, GS was a facility for studying accelerated corrosion of high-temperature water. 209 (2021) 116803 M. Steinbrueck, M. Grosse, U. Stegmaier, J. Braun, C. Lorrette, Oxidation of Silicon Carbide Composites for Nuclear Applications at Very High Temperatures of Steam, Coating 12 (2022) 875
Acknowledgments
Horizon Scorpion received funding from Euratom Research and Training Program 2021-2025 under Grant Agreement No. 101059511. Northwest National Lab), and H2020 IL Trovatore (Grant Agreement No 740415; Euratom Research and Training Program 2014–2018).
About the author
Professor Konstantina Lambrinou is a professor of advanced materials at the Computing Engineering School at Huddersfield University, UK. Her main research interests revolve around accelerated development of advanced nuclear materials, including ATFS. Professor Lambrinou is coordinator of Horizon Scorpion (Grant Agreement No. 101059511) and H2020 IL Trovatore (Grant Agreement No. 740415), European lead for I-Neri Perseus and technical lead for the Westinghouse Gain Program for CR-coated ATF cladding material (NE-23-31246).
detail:
Horizon Scorpion
H2020 IL TROVATORE
This article will also be featured in the 22nd edition of Quarterly Publication.
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