Brittle fracture resistance of reactor pressure vessel steels in the initial state
The effect of chemical and structural inhomogeneity on the resistance to brittle fracture of VVER reactor pressure vessel materials in the initial state (without irradiation) was study in this article. The aim of this work is changing the estimate of brittle fracture resistance using the critical brittleness temperature TC to the estimate of brittle fracture resistance using the brittle viscous transition temperature TP. Also in this study the application of calibrating diagrams for studying the dependence of TP on the grain size and heat treatment is considered.
Comparison between TC and TP for experimental metal of standard 15H2NMFAA steel blanks indicates that TC values are significantly lower than TP values, namely – difference between Tc and TP at lower level of conservatism is 22°C; – difference between Tc and TP at upper level of conservatism is 24°C.
Statistical processing of impact test data array for VVER-1000 and VVER-1200 reactor vessel steels (15H2NMFAA and 15H2NMFA grade 1, respectively) was used. The industrial specimens of the Reactor Pressure Vessel Shells studied in the work were manufactured at the Public Joint Stock Company «Energomashspetsstal» (Kramatorsk, Ukraine).
It was found that when the content of copper in the metal of the surveillance specimens of VVER-1000 RPV is – less than 0.06 wt% heat treatment has a significant effect on the value of TP, which varies from –99°C to –28°C; – between 0.07 to 0.12 wt%, heat treatment does not significantly affect the value of TP, which varies from –60°C to –40°C.
The value of TP practically does not depend on conservatism level.
- PNAE G-7-008-89 Rules of strength calculation for equipment and pipelines of nuclear power plants: Russian Rules and Standards in Nuclear Power Engineering. State Nuclear Energy Supervision the USSR. Moscow. Energy Atomic Publishing, 1987, 525 p. (in Russian).
- RD EO 1.1.2.09.0789-2012. Procedure for VVER-1000 reactor vessel strength and lifetime calculation based on fracture toughness values determined by the surveillance specimens testing: Russian Operating Company Guidance Document. Moscow. JSC «Rosenergoatom». 2012. 56 p. (in Russian).
- RD EO 220.127.116.11.0920-2013. Calculation of brittle fracture resistance for VVER vessels at the design stage: Russian Operating Company Guidance Document. Moscow. JSC «Rosenergoatom». 2012. 63 p. (in Russian).
- TU 0893-013-00212179-2003 Billets of 15H2NMFA, 15H2NMFA-A or 15H2NMFA grade 1 steels for reactor plant vessels, covers, and other components: Russian Technical Standard. Information and Reference system «Teksekspert», 2003, 26 p. (in Russian).
- GOST R ISO 148-1-2013. Metallic materials. Charpy pendulum impact test: Russian standard. Moscow. Russian scientific and technical centre for information on standardization, metrology and conformity assessment, 2014, 46 p. (in Russian).
- Kazantsev A.G., Markochev V.M., Sugirbekov B.A. Estimation of errors in determining critical brittleness temperature of VVER-1000 reactor shell metal using the Monte Carlo method. Tyazhyoloe Mashinostroenie. 2015, iss. 9-10, pp. 19-27 (in Russian).
- Markov S.I. Reference heat treatment methods for VVER type reactor vessel shells. Tyazhyoloe Mashinostroenie. 2011, iss. 8, pp.12-16 (in Russian).
- Surkov A.V., Novozhilov N.M., Anosov N.P. Method for producing an alloy of variable chemical composition: Authors’ Certificate of the USSR No. 642101. Bulletin No. 2, 15.01.1979 (in Russian).
- Dub A.V., Skorobogatykh V.N., Anosov N.P., Zharov V.V., Zubchenko A.S., Piminov V.A., Shamardin V.K. Influence of the chemical and microstructural inhomogeneity of VVER RPV steels on critical brittleness temperature change under irradiation. Atomnaya Energiya. 2012, v. 112, no. 1, pp. 31-38 (in Russian).
- Dub A.V., Skorobogatykh V.N., Anosov N.P., Zharov V.V., Zubchenko A.S., Piminov V.A. Critical brittleness temperature dose-time relationships for predicting VVER-1000 RPV steel lifetime. Atomnaya Energiya. 2011, v. 110, iss. 3, pp. 123-130 (in Russian).
- GOST 5639-82. Steel and alloys. Methods for detection and determination of grain size: Russian standard. Moscow. IPC Publishing House of Standards, 1982, 21 p. (in Russian).
- GOST 9454-78. Metals. Method for testing the impact strength at low, room and high temperature: Russian standard. Moscow. IPC Publishing House of Standards, 1994, 26 p. (in Russian).
- DIN EN ISO 148-1-2011 Metallic materials – Charpy pendulum impact test – Part 1: Test method (ISO 148-1:2009); German version EN ISO 148-1:2010, 35 p.
- Dub A.V., Skorobogatykh V.N., Anosov N.P., Zharov V.V., Zubchenko A.S., PiminovV.A., Shamardin V.K. The error in determining the critical brittleness temperature dose-time relationships for RPV steel welded joints in VVER design. VANT. Ser. Obespechenie bezopasnosty AES. 2011, iss. 30, pp. 126-141 (in Russian).
- Dub A.V., Skorobogatykh V.N., Anosov N.P., GordyukL.Yu., Zubchenko A.S., Shamardin V.K. Statistical modeling of realistic assessment of VVER-1000 RPV materials radiation embrittlement. VANT. Ser. Fizika yadernykh reaktorov. 2016, iss. 2, pp. 24-41 (in Russian).
- Vishkarev O.M., Dub V.S., Loboda A.S., KashirskyYu.V., Shamardin V.K., Zubova T.N., Kalugina I.I., Kobelev N.N. Effect of impurities on radiation resistance of 15H2NMFA pearlitic steel. Trudy TsNIITMASh. 1980, no. 157, pp. 19-24 (in Russian).
- Vishkarev O.M., Dub V.S., Loboda A.S., Shamardin V.K., Kobelev N.N., Kalugina I.I., Zubova T.N. Radiation resistance of 15H2NMFA steel. Trudy TsNIITMASh. 1980, no. 157, pp. 4-6 (in Russian).
- Anosov N.P.,. Krichivets Т.М, Novozhilov N.M., Zubchenko A.S, Tsikunov N.S. Express method for evaluating radiation resistance of weld joints as a function of chemical composition. Avtomaticheskaya Svarka. 1982, no. 6 (351), pp. 62-63 (in Russian).
- Anosov N.P., Novozhilov N.M., Evseyev S.I., Amayev A.D., Kryukov A.M., Sokolov M.A. Estimating chemical composition dependence of weld joint metal radiation embrittlement. Avtomaticheskaya Svarka. 1985, no. 10 (391), pp. 66-68 (in Russian).
- Anosov N.P., Novozhilov N.M., Zubchenko A.S., Kolesova T.N., Pecherin A.M., Shamardin V.K. Radiation resistance evaluation for 15H2NMFAA weld joint fusion zone metal using seams of variable chemical composition. Avtomaticheskaya Svarka. 1990, no. 11 (452), pp. 7-10 (in Russian).