Neutronic evaluation of coating and cladding materials for accident tolerant fuels

Abstract

a b s t r a c tIn severe accident conditions with loss of active cooling in the core, zirconium alloys, used as fuel cladding materials for current light water reactors (LWR), undergo a rapid oxidation by high temperature steam with consequent hydrogen generation. Novel fuel technologies, named accident tolerant fuels (ATF), seek to improve the endurance of severe accident conditions in LWRs by eliminating or at least mitigating such detrimental steam-cladding interaction. Most ATF concepts are expected to work within the design framework of current and future light water reactors, and for that reason they must match or exceed the performance of conventional fuel in normal conditions. This study analyzed the neutronic performance of ATF when employed in both pressurized and boiling water reactors. Two concepts were evaluated: (1) coating the exterior of zirconium-alloy cladding with thin ceramics to limit the zirconium available for reaction with high-temperature steam; (2) replacing zirconium alloys with alternative materials possessing slower oxidation kinetics and reduced hydrogen production. Findings show that ceramic coatings should remain 10e30 mm thick to limit the neutronic penalty. Alternative cladding materials, with the exception of SiC, enhance neutron loss compared to zirconium-alloys. An extensive parametric analysis concluded that reference performance metrics can be met by employing 300-mm or less thick cladding or increasing fuel enrichment by up to 1.74% depending on material and geometry.

Materials selection for nuclear applications: Challenges and opportunities

“…3, we can see that Mo has a macroscopic thermal-neutron absorption cross-section that is more than an order of magnitude higher than that of Zr. This significant increase in neutron absorption would have drastic effects on the neutronics of the core and could have major ramifications, as seen in [18]. Considering iron-based alloys, we observe that Fe and its traditional alloying elements (Cr, nickel (Ni), etc.)…”

“…Four systems have been studied: 1) silicon-carbide (SiC)-based composites [16][17][18], 2) iron-chromium-aluminum (Fe-Cr-Al) alloys [19,[21][22][23], 3) coated zirconium [24], and 4) molybdenum (Mo) [25]. These four systems were chosen as balanced compromise among the application's requirements.…”

“…Therefore, possible enriching of the other isotopes 1 (removal of the 95 Mo) would result in the bulk Mo component maintaining its chemical and mechanical properties but changing its nuclear properties to a more favorable state (Fig. 3B) [18].…”

Neutronic Analysis of the Candidate Multi-Layer Cladding Materials With Enhanced Accident Tolerance for Wwer Reactors

“…Many of the recent papers and reports focused on neutronic performance of ATF fuel concepts for traditional PWR and BWR reactors [8][9][10][11]. However, the ATF fuels can and should be employed also in the WWER reactors that are in operation in the Czech Republic, Bulgaria, Slovakia, Hungary, Finland, Ukraine, India, and Russia.…”

ZrC COATING ON FUEL ELEMENT CLADDING ZIRCALOY-2

“…This results in the degradation of the mechanical properties of the zirconium cladding due to the increased radiation damage, corrosion and hydrogen uptake, as well as increased fission gas inventory [3] . To allow more efficient operation during normal reactor operating conditions with higher safety margins, nuclear fuel research and development (R&D) work focus on the development of an advanced fuel cladding system [1] with slower oxidation rates, reduced hydrogen pick-up, and limited irradiation growth as well as creep of the cladding during the long-term normal operation [4][5] .…”