A.A. BOCHVAR HIGH-TECHNOLOGY RESEARCH INSTITUTE OF INORGANIC MATERIALS (JSC «VNIINM») 19TH INTERNATIONAL SYMPOSIUM ON ZIRCONIUM IN THE NUCLEAR INDUSTRY MAY 20-23, 2019, Manchester, UK « ROSATOM » STATE ATOMIC ENERGY CORPORATION Fabrication of E110 Alloy Fuel Rod Claddings on Electrolytic Zirconium Base with Removing Fluorine Impurity for Providing Resistance to Breakaway Oxidation in High-Temperature Steam V. Markelov 1 , A. Malgin 1 , N. Filatova 1 , V. Novikov 1 , A. Shevyakov 1 , A. Gusev 1 , I. Shelepov 1 , A. Golovin 1 , A. Ugryumov 2 , A. Dolgov 2 , A. Ziganshin 3 , V. Donnikov 4 , V. Latunin 4 1) 2) 3) 4)
Introduction. Problem essence. The E110 alloy is used as the fuel rod claddings of VVER reactors. Electrolytic zirconium powder with additives of iodide zirconium and remains of zirconium production from these materials is used as a charge basis for the standard version of alloy. The ingots are smelted by double vacuum arc melting (VAM). Fuel rods with E110 alloy cladding satisfy the design parameters of operation. At the same time the E110 alloy under certain high-temperature conditions of the LOCA design basis accident is characterized by appearance of breakaway oxidation. In [9] on the basis of phenomenological ideas about the mechanism of influence on oxidation of various impurities it was stated that the breakaway effect of E110 alloy was caused by the presence of residual fluorine ( F ) impurity, which accompanied the fluoride technology for producing of electrolytic powder. [9] Chung Hee M., «Fuel behavior under loss-coolant accident situations» // Nuclear Engineering and Technology, vol.37, № 4, August, 2005, p. 327-362. 19 TH INTERNATIONAL SYMPOSIUM ON 2 ZIRCONIUM IN THE NUCLEAR INDUSTRY MAY 20-23, 2019, Manchester, UK
Introduction. Ways to solve the problem. Breakaway oxidation does not appear on the E110 alloy with a charge based on sponge zirconium, in which F impurity is practically absent. In [8] the negative effect of F was confirmed experimentally by comparative studies of resistance to breakaway oxidation of fuel rod claddings made of ingots from electrolytic zirconium based alloy after two, three and four melts. It is shown that the key factor of a pronounced early breakaway effect of the standard E110 alloy after 400-500 s of steam oxidation at 1000 ºС is the residual content of F in the amount of 4-5 ppm. The content of F decreased to less than 1 ppm after four melts of the ingot and breakaway effect at 1000 ° C does not appear at least during oxidation up to 5,000 s which corresponds to 20% ECR C-P . [8] Markelov, V.A., Malgin, A.G., Novikov , V.V. “Providing durability in a LOCA design basis accident of fuel rod cladding made of electrolytic zirconium E110 alloy”, Presented at the 2017 WRFPM, Jeju Island, Korea, September 10-14, 2017, Paper No F-162 19 TH INTERNATIONAL SYMPOSIUM ON 3 ZIRCONIUM IN THE NUCLEAR INDUSTRY MAY 20-23, 2019, Manchester, UK
Introduction. Aim and tasks of the work. At the same time melts regimes were not specifically worked out but corresponded to the current technological documentation for the melting of E110 alloy ingots. The aim of this work was to develop a new technological process for manufacturing of industrial ingots of the electrolytic zirconium based E110 alloy to ensure a guaranteed and maximally uniform content of residual F impurity in the ingot volume less than 1 ppm . At the same time the tasks were to optimize the regimes and methods of melting and to achieve the result using the least number of ingot melts. Fuel rod claddings made of ingots manufactured by the new technology were tested to breakaway oxidation resistance and as shown by the results satisfy criterion of the material safety in conditions of LOCA design basis accident with margin. 19 TH INTERNATIONAL SYMPOSIUM ON 4 ZIRCONIUM IN THE NUCLEAR INDUSTRY MAY 20-23, 2019, Manchester, UK
Scheme of standard manufacturing technology of E110 alloy ingots and cladding tubes 19 TH INTERNATIONAL SYMPOSIUM ON 5 ZIRCONIUM IN THE NUCLEAR INDUSTRY MAY 20-23, 2019, Manchester, UK
Dynamics of reduction of F content in the manufacture of E110 alloy ingots based on electrolytic zirconium EBM – Electron Beam Melting Using of EBM makes possible to remove F more efficiently compared to the VAM. This feature of EBM is due to the high vacuum in the chamber of the electron-beam facility, the fully open surface of the melt in the ingot mold and the possibility to widely vary the power and rate of melting Ion chromatography (Dionex ICS-2100 unit) was used to determine the F content quantitatively, which has the detection limit of 0.5 ppm and the error of 15-44% in the range of F concentrations of 0.5-100.0 ppm (the smaller F content the higher error value). Three samples per point were analyzed and the mean values were determined. [8] Markelov, V.A., Malgin, A.G., Novikov , V.V. “Providing durability in a LOCA design basis accident of fuel rod cladding made of electrolytic zirconium E110 alloy”, Presented at the 2017 WRFPM, Jeju Island, Korea, September 10-14, 2017, Paper No F-162 19 TH INTERNATIONAL SYMPOSIUM ON 6 ZIRCONIUM IN THE NUCLEAR INDUSTRY MAY 20-23, 2019, Manchester, UK
New technology manufacturing of E110 ingots Electron Beam Billet Vacuum System F F F Drops Bath with liquid metal Crystallizer Ingot 𝐷 0 𝐷 = 𝑔(𝑄 𝑡 , 𝑊) where: C 0 – initial F concentration in the consumable billet, mole/m 3 ; C – F concentration in the ingot after EBM, mole/m 3 ; P s – specific melting power of EBM, kW/cm 2 ; V – melting rate, kg/h. 19 TH INTERNATIONAL SYMPOSIUM ON 7 ZIRCONIUM IN THE NUCLEAR INDUSTRY MAY 20-23, 2019, Manchester, UK
Dependence of E110 alloy fluorine refinement coefficient on EBM parameters Optimized EBM parameters 9 ingots compared to the fourfold melting scheme (VAM-VAM- EBM-VAM) in [8] were applied to melt for the ingot in the new technical process based on the obtained dependence: - specific melting power ( P spec ) is increased by ~ 20%; - melting rate ( V ) is reduced by ~ 80%. [8] Markelov, V.A., Malgin, A.G., Novikov , V.V. “Providing durability in a LOCA design basis accident of fuel rod cladding made of electrolytic zirconium E110 alloy”, Presented at the 2017 WRFPM, Jeju Island, Korea, September 10-14, 2017, Paper No F-162 19 TH INTERNATIONAL SYMPOSIUM ON 8 ZIRCONIUM IN THE NUCLEAR INDUSTRY MAY 20-23, 2019, Manchester, UK
Ingots and sampling scheme of fluorine analysis Sampling scheme of fluorine content Ingot appearance after first distribution analysis in longitudinal EBM melting (a) and after (c) and in radial (d) directions in second EBM-VAM melting (b) ingot (c) (d) 19 TH INTERNATIONAL SYMPOSIUM ON 9 ZIRCONIUM IN THE NUCLEAR INDUSTRY MAY 20-23, 2019, Manchester, UK
Fluorine content distribution in the ingot after each melting 2.7 EBM EBM-VAM 2.3 EBM-VAM-VAM EBM-VAM-VAM-VAM 19 TH INTERNATIONAL SYMPOSIUM ON 10 ZIRCONIUM IN THE NUCLEAR INDUSTRY MAY 20-23, 2019, Manchester, UK
Average fluorine content in semi-finished products and cladding tubes Average fluorine content, ppm Billet after Hot Tube after Tube after Cladding Melting scheme Billet mechanical extrusion 1-st 2-nd tube (2 pc.) treatment sleeve pillgering pillgering (10 pc.) (18 pc.) (18 pc.) (10 pc.) (10 pc.) 0,75 ± 0,05 0,70 ± 0,05 0,79 ± 0,06 0,83 ± 0,06 0,86 ± 0,06 0,89 ± 0,06 EBM-VAM-VAM 0,72 ± 0,05 0,65 ± 0,05 0,62 ± 0,05 0,72 ± 0,05 0,77 ± 0,06 0,85 ± 0,06 EBM-VAM-VAM-VAM The total of 465 samples taken from ingots melted three and four times semi-finished and finished tubes were analyzed for F content. All data showed that the concentration of F in the metal is below 1 ppm . This result indicates that the new technology of melting the electrolytic zirconium based E110 alloy ensures sufficiently uniform distribution of F throughout the ingot and the required quantity. 19 TH INTERNATIONAL SYMPOSIUM ON 11 ZIRCONIUM IN THE NUCLEAR INDUSTRY MAY 20-23, 2019, Manchester, UK
Resistance to breakaway oxidation in high-temperature steam The most pronounced breakaway effect at high temperature steam oxidation for fuel claddings made from the E110 alloy appears at the temperature of 1000 ºС . Therefore, the oxidation tests for evaluating E110 alloy breakaway resistance were conducted at that temperature. Impurity elements content in ingots of investigated materials Impurity element, ppm Melting Alloy marking С scheme Fe O Ni N Si Al Cr F EBM-VAM-VAM E110-3m 100 400 20 30 65 30 20 15 0.8 EBM-VAM-VAM-VAM E110-4m 100 390 20 30 70 30 20 15 0.7 VAM-VAM E110-2m (lot1) 100 600 30 25 100 25 20 20 4-5 VAM-VAM E110-2m (lot2) 160 520 40 20 55 30 20 30 2-3 E110opt VAM-VAM-VAM 510 820 30 30 60 30 25 40 <1.0 Sponge based Reference material 19 TH INTERNATIONAL SYMPOSIUM ON 12 ZIRCONIUM IN THE NUCLEAR INDUSTRY MAY 20-23, 2019, Manchester, UK
Oxidation procedure and examination of tube samples Full length cladding tube / sampling scheme (E110-2m/lot2; E110-3m; E110-4m) VTI experimental setup High-temperature oxidation scheme Oxidation Kinetics Appearance analysis RCT at 135 ° C Max oxidation time for E110-2m - 4000 s Microstructure analysis for E110-3m, E110-4m, E110opt – 10,000 s Hydrogen measurements 19 TH INTERNATIONAL SYMPOSIUM ON 13 ZIRCONIUM IN THE NUCLEAR INDUSTRY MAY 20-23, 2019, Manchester, UK
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