National Research Nuclear University MEPhI, Moscow, Russia¹ ; National Nuclear Research Center, Baku, Azerbaijan² ; Joint Institute for Nuclear Research, Dubna, Russia³:

R. Sh. Isayev, Postgraduate Student¹, Engineer at the Institute of Nuclear Physics and Technology¹, Junior Research Fellow², Engineer³

National Research Nuclear University MEPhI, Moscow, Russia:
D. A. Safonov, Engineer at the Department of Physical Problems of Materials Science
P. S. Dzhumaev, Associate Professor at the Institute of Nuclear Physics and Technology, Candidate of Technical Sciences, e-mail: PSDzhumaev@mephi.ru

National Research Nuclear University MEPhI, Moscow, Russia¹ ; Belarusian State University, Minsk, Belarus²:
E. L. Korenevskiy, Postgraduate Student¹, Engineer at the Institute of Nuclear Physics and Technology1, Engineer of the RL of ion-plasma modification of solids physics²

Loss-of-coolant accidents (LOCAs) often lead to dire consequences. That’s why the global community are actively engaged in research aimed at creating accident tolerant fuels. One of the areas of such research is preserving zirconium alloys as the material for fuel-element claddings by creating corrosion-resistant coatings that would be in contact with the coolant. Chromium could be a promising material to be used in such protective coatings as chromium oxide (Cr₂O₃) serves as an effective barrier for oxygen both in normal operation and in case of LOCA. Chromium coating hinders oxygen diffusion into the metal substrate and thus prevents embrittlement and failure of the fuel-element cladding. This paper describes the results of research studies that have been carried out in recent years and that look at the resistance of magnetron sputtered chromium coatings to high-temperature oxidation in water vapour up to 1,500 ^oC. The paper demonstrates advantages and drawbacks of chromium coatings in hightemperature oxidation conditions. The focus is on understanding how regimes of magnetron sputtering influence the resistance of chromium coatings to high-temperature oxidation and how the structure and phase state of chromium coatings are related to their properties. The authors describe the optimal regimes of magnetron sputtering for obtaining dense coatings and examine the effect of the substrate temperature and the bias voltage on the structure and density of resulting coatings. High Power Impulse Magnetron Sputtering (HiPIMS) serves as an effective technique that helps enhance the density of coatings. The conclusion drawn is that in order to broaden the temperature range in which chromium coatings can effectively protect zirconium alloys from failure up to 1500 ^oC, there should be a diffusion barrier between the surface of the fuel-element cladding and the chromium coating.

The authors would like to thank B. A. Kalin, supervisor of this project, who had passed away before this publication was made. The staff of the Laboratory of Ion-Plasma and Ion-Beam Machining of Materials, a part of Department No. 9 at the National Research Nuclear University MEPhI, devote this paper to his memory.

1. Terrani K. A. Accident tolerant fuel cladding development: Promise, status, and challenges. Journal of Nuclear Materials. 2018. Vol. 501. pp. 13–30.
2. Zavodinsky V. G. The mechanism of ionic conductivity in stabilized cubic zirconia. Physics of the Solid State. 2004. Vol. 46, No. 3. pp. 453–457.
3. Kritskiy V. G., Kalin B. A. Corrosion of fuel-element claddings in a life cycle of light-water reactor fuel assemblies. Moscow : Izdatelstvo “MIFI”, 2020. 200 p.

4. Gussev M. N., Byun T. S., Yamamoto Y. In-situ tube burst testing and hightemperature deformation behavior of candidate materials for accident tolerant fuel cladding. Journal of Nuclear Materials. 2015. Vol. 466. pp. 417–425.
5. Michalik M., Hansel M. Effect of water vapour on growth and adherence of chromia scales formed on Cr in high and low pO₂-environments at 1000 and 1050 ^oC. Materials at High Temperatures. 2005. Vol. 22, No. 3-4. pp. 213–221.
6. Arifin S. K. et al. Effects of water vapor on protectiveness of Cr₂O₃ scale at 1073 K. IOP Conference Series: Materials Science and Engineering. ICAMME 2017, 8–9 August, Cuala, Malaysia. 2018. Vol. 290, No. 1. 012085.
7. Brachet J. C., Idarraga-Trujillo I., Flem M. L., Saux M. L. et al. Early studies on Cr-сoated Zircaloy-4 as enhanced accident tolerant nuclear fuel claddings for light water reactors. Journal of Nuclear Materials. 2019. Vol. 517. pp. 268–285.
8. Maier B., Yeom H., Johnson G., Dabney T., Walters J. et al. Development of cold spray chromium coatings for improved accident tolerant zirconiumalloy cladding. Journal of Nuclear Materials. 2019. Vol. 519. P. 247–254.
9. Ševecek M., Gurgen A., Phillips B., Che Y., Wagih M. et al. Cold spray Crcoated fuel cladding with enhanced accident tolerance. In Proceedings of the 2017 Water Reactor Fuel Performance Meeting. Ramada Plaza Jeju, Jeju Island, Korea, 2017. 10–14 September.
10. Kim H. G., Kim I. H., Jung Y. I., Park D. J., Park J. Y. et al. Adhesion property and High-temperature oxidation behavior of Cr-coated Zircaloy-4 cladding tube prepared by 3D laser coating. Journal of Nuclear Materials. 2015. Vol. 465. pp. 531–539.
11. Bischoff J., Delafoy C., Vauglin C., Barberis P., Roubeyrie C. et al. AREVA NP’s enhanced accident-tolerant fuel developments: Focus on Cr-coated M5 cladding. Nuclear Engineering and Technology. 2018. Vol. 50, Iss. 2. pp. 223–228.
12. Syrtanov M. S. et al. High-temperature oxidation of Zr – 1Nb zirconium alloy with protective Cr/Mo coating. Surface and Coatings Technology. 2022. Vol. 439. 128459.
13. Wei T., Zhang R., Yang H., Liu H., Qiu S. et al. Microstructure, corrosion resistance and oxidation behavior of Cr-coatings on Zircaloy-4 prepared by vacuum arc plasma deposition. Corrosion Science. 2019. Vol. 158. 108077.
14. Wang Y., Zhou W., Wen Q., Ruan X., Luo F. et al. Behavior of plasma sprayed Cr coatings and FeCrAl coatings on Zr fuel cladding under loss-ofcoolant accident conditions. Surface and Coatings Technology. 2018. Vol. 344. pp. 141–148.
15. Park J. H., Kim H. G., Park J. Y., Jung Y. I., Park D. J. et al. High temperature steam-oxidation behavior of arc ion plated Cr coatings for accident tolerant fuel claddings. Surface and Coatings Technology. 2015. Vol. 280. pp. 256–259.
16. Bischoff J., Delafoy C., Chaari N., Vauglin C., Buchanan K. et al. Crcoated cladding development at framatome. In Proceedings of the Top Fuel 2018. Prague, Czech Republic, 30 September – 4 October 2018. A0152.
17. Kim H. G., Kim I. H., Jung Y. I., Park D. J., Park J. H. Oxidation behavior and mechanical property of Cr-coated zirconium cladding prepared by 3D laser coating. In Proceedings of the 2014 Water Reactor Fuel Performance Meeting (WRFPM 2014), Sendai, Japan. 2014. 14–17 September. No. 100054.
18. Kalin B. A., Yashin A. S., Dzhumaev P. S., Safonov D. A. et al. Features of creating wear-resistant anti-corrosion coatings with a barrier layer on fragments of fuel claddings from E110 o. ch. IOP Conference Series: Materials Science and Engineering. IOP Publishing, 2020. Vol. 1005, No. 1. 012009.
19. Nguyen D. V., Le Saux, Gelebant L. et al. Mechanical behavior of a chromium coating on a zirconium alloy substrate at room temperature. Journal of Nuclear Materials. 2022. Vol. 558. 153332.
20. Kuprin А. S., Belous V. A., Voevodin V. N., Bryk V. V. et al. Vacuum-arc chromium-based coatings for protection of zirconium alloys from the hightemperature oxidation in air. Journal of Nuclear Materials. 2015. Vol. 465. pp. 400–406.
21. Jiang L. et al. Effects of ion irradiation on chromium coatings of various thicknesses on a zirconium alloy. Journal of Nuclear Materials. 2019. Vol. 526. 151740.
22. Krej J., Kabtov J., Manoch F., Ko J., Cvrlek J. et al. Development and testing of multicomponent fuel cladding with enhanced accidental performance. Nuclear Engineering and Technology. 2020. Vol. 52. pp. 597–609.
23. Brachet J., Le Saux M., Bischoff J., Palancher H., Chosson R. et al. Evaluation of equivalent cladding reacted parameters of Cr-coated claddings oxidized in steam at 1200 ^oC in relation with oxygen diffusion/partitioning and post-quench ductility. Journal of Nuclear Materials. 2020. Vol. 533. 152106.
24. Yun D., Chenyang L., Zangian Z. et al. Current state and prospect on the development of advanced nuclear fuel system materials: A review. Materials Reports: Energy. 2021. Vol. 1, Iss. 1. 100007.

25. Duan Z., Yang H., Satoh Y. et al. Current status of materials development of nuclear fuel cladding tubes for light water reactors. Nuclear Engineering and Design. 2017. Vol. 316. pp. 131–150.
26. Wadsack R., Pippan R., Schedler B. The effect of pre-deformation on the ductility of chromium. Journal of Nuclear Materials. 2002. Vol. 307, Part 1. pp. 701–704.
27. Arias D., Abriata J. P. The Cr – Zr (chromium – zirconium) system. Bulletin of Alloy Phase Diagrams. 1986. Vol. 7, No. 3. pp. 237–244.
28. Nobre G. P. A., Pigni M. T., Brown D. A. et al. Newly evaluated neutron reaction data on chromium isotopes. Nuclear Data Sheets. 2021. Vol. 173. pp. 1–41.
29. Gu Y. F., Harada H., Ro Y. Chromium and chromium-based alloys: Problems and possibilities for high-temperature service. JOM. 2004. Vol. 56. pp. 28–33.
30. Berlin E. V., Grigoriev V. Yu., Ivanov A. V., Isaenkova M. G., Klyukova K. E., Stolbov S. D. Structure of the protective chromium coating obtained by a thermal evaporation method in a magnetron discharge on the cladding tube from E110 alloy. Tsvetnye Metally. 2019. No. 4. pp. 33–40. DOI: 10.17580/tsm.2019.04.04.
31. Karpyuk L. A., Krasnobaev N. N., Maslov A. A., Novikov V. V., Orlov V. K. et al. Magnetron sputtering of heat-resistant coatings on accident tolerant fuel claddings. Voprosy atomnoy nauki i tekhniki. Seriya: Materialovedenie i novye materialy. 2020. No. 5. pp. 4–37.
32. Haynes W. M., Lide D. R., Bruno T. J. CRC handbook of chemistry and physics (2^nd ed.). CRC press, 2016. 2664 p.
33. Brachet J.-C., Le Flem M., Le Saux M. L. et al. Early studies on Cr-Coated Zircaloy-4 as enhanced accident tolerant nuclear fuel claddings for light water reactors. Journal of Nuclear Materials. 2019. Vol. 517. pp. 268–285.
34. Brachet J. C., Gulbert T., Saux M. L. et al. Behavior of Cr-coated M5 claddings during and after high temperature steam oxidation from 800 ^oC up to 1500 ^oC (Loss-of-Coolant Accident & Design Extension Conditions). Proceedings of the Topfuel. 2018. ID 211 48 2151.
35. Krejсí J., Celevec M., Kabatova G. et al. Chromium and chromium nitride coated cladding for nuclear reactor fuel. EUROCORR 2017: Proceedings of the 20^th International Corrosion Congress and Process Safety Congress. 2017. Vol. 2017.
36. Krejсí J., Ševecek M., Kabatova J., Manoch F., Kocí J. et al. Experimental behavior of chromium-based coatings. Proceedings of the TopFuel 2018, Prague, Czech Republic, 2018. 30 September – 4 October.
37. Shelepov I. A., Malgin A. G., Markelov V. A., Shevyakov A. Yu., Novikov V. V. et al. Resistance to high-temperature oxidation in a design LOCA event involving zirconium claddings with chromium coating designed for accident tolerant fuel elements. Voprosy atomnoy nauki i tekhniki. Seriya: Materialovedenie i novye materialy. 2020. No. 4. pp. 17–27.
38. Han X., Chen Ch., Tan Y. et al. A systematic study of the oxidation behavior of Cr coatings on Zry4 substrates in high temperature steam environment. Corrosion Science. 2020. Vol. 174. 108826.
39. Isaenkova M. G., Perlovich Yu. A., Stolbov S. D., Klyukova K. E., Fesenko V. A., Berlin E. V. Influence of technology of obtaining chromium coating on cladding tubes from Zr – 1% Nb – (O, Fe) alloy on change of its structure during air oxidation at temperatures 400–1150 ^oC. Tsvetnye Metally. 2020. No. 2. pp. 66–75. DOI: 10.17580/tsm.2020.02.09.
40. Li G., Liu Y., Zhang Y. et al. High Temperature Anti-Oxidation Behavior and Mechanical Property of Radio Frequency Magnetron Sputtered Cr Coating. Metals (Basel). 2020. Vol. 10, No. 11. 1509.
41. Kashkarov E. B., Sidelev D. V., Syrtanov M. S., Tang C., Steinbrck M. Oxidation kinetics of Cr-coated zirconium alloy: Effect of coating thickness and microstructure. Corrosion Science. 2020. Vol. 175. 108883.
42. Kashkarov E. B., Sidelev D. V., Rombaeva M., Syrtanov M. S. et al. Chromium coatings deposited by cooled and hot target magnetron sputtering for accident tolerant nuclear fuel claddings. Surface and Coatings Technology. 2020. Vol. 389. 125618.
43. Huang J. et al. Microstructural, mechanical properties and high temperature oxidation of Cr, Al-coated Zr-4 alloy. Nuclear Materials and Energy. 2020. Vol. 25. 100810.
44. Chen Q. S. et al. Microstructure and high-temperature steam oxidation properties of thick Cr coatings prepared by magnetron sputtering for accident tolerant fuel claddings: The role of bias in the deposition process. Corrosion Science. 2020. Vol. 165. 108378.
45. Chen Q. et al. Microstructure evolution and adhesion properties of thick Cr coatings under different thermal shock temperatures. Surface and Coatings Technology. 2021. Vol. 417. 127224.
46. He X. et al. Effect of gas pressure and bias potential on oxidation resistance of Cr coatings. Annals of Nuclear Energy. 2019. Vol. 132. pp. 243–248.