Izvestia Vysshikh Uchebnykh Zawedeniy. Yadernaya Energetika

The peer-reviewed scientific and technology journal. ISSN: 0204-3327

Design and experimental assessment of thermal stratification influence on operational loading of surge line of Novovoronezh NPP, unit №5

3/22/2017 2011 - #01 Nuclear power plants

Povarov V.P. Urazov O.V. Bakirov M.B. Levchuk V.I.

DOI: https://doi.org/10.26583/npe.2017.1.01

UDC: 621.311.25

One of the main tasks of NPP lifetime justification consists in detailed consideration of all factors affecting the residual life of critical NPP components. Particular attention should be paid to studying the phenomenon of thermal stratification (TS), which is the effect of coolant lamination to the “cold” and “hot” layer in a horizontal pipelines while flows having different temperatures stream with slow rates. The relevance of this issue is stipulated for the fact that cyclic loads caused by TS result in accumulation of metal damage due to thermal fatigue and can initiate formation and accelerated growth of defects.

The work is devoted to complex analysis of coolant TS observed in the horizontal runs of the surge line (SL) on WWER-1000 units. Comprehensive assessment of TS effects on a stress-strain state and cyclic damage accumulation of metal was also made. The experimental data regarding the distribution of temperature fields in horizontal SL sections, as well as cyclic loading history during several reactor campaigns were recorded by on-line monitoring system, put into operation on Novovoronezh NPP, Unit 5. Data analysis allowed to establish some distinctive features of TS in SL of Unit 5, depending on operational modes. The most significant TS effects were observed in the control section located in the first horizontal run nearby the pressurizer.

Experimental records were used as initial data for calculations which were provided in order to evaluate the stress-strain state of SL considering TS effects. Results of stress analysis allow to conclude that actually observed effects of thermal stratification and thermal fatigue have a significant impact on SL lifetime. Indicated by calculations areas, in which maximum accumulated damage is observed, coincide with places of operational defects being revealed during outage of Unit 5. As a compensatory measure aimed at increasing the SL residual life, it is proposed the procedure of treatment of SL weld joints using the method of surface plastic deformation.

References

  1. Sharyj N.V., Semishkin V.P., Piminov V.A., Dragunov Ju.G. Prochnost’ osnovnogo oborudovaniya i truboprovodov reaktornyh ustanovok VVER [Strength of main equipment and pipelines of WWER reactor assemblies]. Moscow. IzdAT Publ. 2004. 496 p. (in Russian).
  2. Sharyj N.V. Aktual’nye problemy raschyotnogo obosnovaniya prochnosti reaktornyh ustanovok VVER i puti ih resheniya [Topical problems of strength calculation of VVER reactor assemblies and ways of solving]. VANT. Ser. Obespechenie bezopasnosti AES., 2010, iss. 27, pp. 5-21 (in Russian).
  3. IPSN/OECD-NEA/WANO. Specialists meeting on experience with thermal fatigue in LWR piping caused by mixing and stratification. Proceedings. Paris, 1998. Available at: https://www.oecd-nea.org/nsd/docs/1998/csni-r98-8.pdf (accessed 24 Jan. 2017).
  4. Berkovich V.Ya., Bogachev A.V., Muravin D.B., Fomin A.V. Raschet nagruzhajuschih faktorov po pokazaniyam shtatnyh datchikov sistemoj SAKOR0320 na 2 energobloke Rostovskoj AES [Calculation of loading factors SACOR-320 by indications of standard detectors on Rostov NPP, unit 2]. The VII-th International scientific and technical conference «Safety Assurance of NPP with WWER». Podol’sk, OKB «Gidropress», 2011 (in Russian). Available at: http://www.gidropress.podolsk.ru/files/proceedings/mntk2011/documents/mntk2011-111.pdf (accessed 24 Jan. 2017).
  5. Saunin Yu.V., Dobrotvorskij A.N., Semenihin A.V. Issledovanie faktorov, opredelyayuschih temperaturnuyu stratifikaciyu teplonositelya v gorjachih nitkah petel’ 10go kontura RU s VVER01000 [Examination of factors, determining the coolant thermal stratification in hot legs of primary circuit loops of RP with WWER-1000]. The VII-th international scientific and technical conference «Safety Assurance of NPP with WWER». Podol’sk, OKB «Gidropress», 2013 (in Russian). Available at: http://www.gidropress.podolsk.ru/files/proceedings/mntk2013/autorun/article133-ru.htm (accessed 24 Jan. 2017).
  6. IAEA-TECDOC-1361. Assessment and management of ageing of major nuclear power plant components important to safety. Primary piping in PWRs. International Atomic Energy Agency, 2003. Available at: http://www-pub.iaea.org/MTCD/Publications/PDF/te_1361_web.pdf (accessed 24 Jan. 2017).
  7. NUREG-1801. The Generic Aging Lessons Learned (GALL) Report. United States Nuclear Regulatory Commission, 2010. Available at: https://www.nrc.gov/docs/ML1034/ML103490041.pdf (accessed 24 Jan. 2017).
  8. Safe management of the operating lifetimes of nuclear power plants INSAG-14. A report by the International Nuclear Safety Advisory Group. International Atomic Energy Agency, 1999. Available at: http://www-pub.iaea.org/MTCD/publications/PDF/P085_scr.pdf (accessed 24 Jan. 2017).
  9. Bakirov M.B., Levchuk V.I., Kiselev A.S. Analiz termosilovoj nagruzhennosti dyhatel’nogo truboprovoda i ocenka ostatochnogo resursa s uchetom vliyaniya termicheskoj stratifikacii i stareniya metalla v period sverhproektnogo sroka sluzhby energobloka № 5 NVAES [Analysis of thermal loads in the surge line and assessment of its residual lifetime considering effects of thermal stratification and metal ageing during long term operation of Novovoronezh NPP, Unit 5]. Technical report № 03/14-2. CMSLM Ltd., 2014 (in Russian).
  10. Bakirov M.B., Levchuk V.I., Kiselev A.S. Analiz termosilovoj nagruzhennosti dyhatel’nogo truboprovoda i ocenka ostatochnogo resursa s uchetom vliyanija termicheskoj stratifikacii v period sverhproektnogo sroka sluzhby energobloka № 5 NVAES po dannym monitoringa, zapisannym v techenie 310j toplivnoj kampanii [Analysis of thermal loads in the surge line and assessment of its residual lifetime considering effects of thermal stratification during long term operation of Novovoronezh NPP, Unit 5 using monitoring data obtained during 31 fuel campaign]. Technical report № 03/15-2. CMSLM Ltd., 2015 (in Russian).
  11. Rezepov V.K., Denisov V.P., Kirilyuk N.A., Dragunov Yu.G., Ryzhov S.B. Reaktory VVER0 1000 dlja atomnyh elektrostancij [Reactors WWER-1000 for nuclear power plants]. Moscow, Akademkniga Publ., 2004. 333 p. (in Russian).
  12. Bakirov M.B., Povarov V.P. Sistema mnogoparametricheskogo nepreryvnogo monitoringa ekspluatacionnoj povrezhdaemosti oborudovaniya atomnoj elektrostancii [System of multi-parametric on-line monitoring of operational damageability of nuclear power plant equipment]. Russian Federation. Patent for invention № 2574578. Request №2014104752/07 12.02.2014. Published: 10.02.2016 (in Russian).
  13. Bakirov M.B., Levchuk V.I., Kiselev A.S. Sbor, obrabotka i analiz dannyh monitoringa termicheskoj stratifikacii dyhatel’nogo truboprovoda 5 bloka NVAES v razlichnyh rezhimah ekspluatacii reaktornoj ustanovki [Collection, processing and analysis of monitoring data concerning thermal stratification in the surge line of Novovoronezh NPP, Unit 2 in various operational modes of the reactor facility]. Technical report № 03/14-1. CMSLM Ltd., 2014 (in Russian).
  14. Bakirov M.B., Levchuk V.I., Kiselev A.S. Sbor, obrabotka i analiz dannyh, zapisannyh sistemoj monitoringa termicheskoj stratifikacii dyhatel’nogo truboprovoda pri rabote na moshhnosti i ostanove energobloka № 5 NVAES v techenie 310j toplivnoj kampanii [Collection, processing and analysis of monitoring data recorded by the thermal stratification monitoring system of the surge line during power operation and cooldown of Novovoronezh NPP, Unit 5 during 31 fuel campaign]. Technical report № 03/15-1. CMSLM Ltd., 2014 (in Russian).
  15. Ovchinnikov F.Ya., Semenov V.V. Ekspluatacionnye rezhimy vodo0vodjanyh energeticheskih reaktorov [Operational modes of pressurized water reactors]. Moscow. Energoatomizdat Publ. 1988. 359 p. (in Russian).
  16. Kiselev A.S., Kiselev A.S., Danichev V.V. Annotacija programmy UZOR1 [Annotation of the software UZOR1]. VANT. Ser. Fizika yadernyh reaktorov. 1999, iss. 1, pp. 109-113 (in Russian).
  17. Postnov V.A., Dmitriev S.P. Metod superelementov v raschetah inzhenernyh sooruzhenij [The method of super elements in calculations of engineering structures]. Leningrad. Sudostroenie Publ. 1979. 287 p. (in Russian).
  18. Oborudovanie i truboprovody atomnyh energeticheskih ustanovok. Svarka i naplavka. Osnovnye polozheniya [Equipment and pipelines of atomic electric power plants. Welding and cladding. General provisions]. PNAE G-7-009-89. Moscow. Energoatomizdat Publ. 1991. 136 p. (in Russian).
  19. Normy rascheta na prochnost’ oborudovaniya i truboprovodov atomnyh energeticheskih ustanovok [Norms for strength calculations of equipment and pipelines of atomic electric power plants]. PNAE G-7-002-86. Moscow. Energoatomizdat Publ. 1989. 525 p. (in Russian).
  20. Odincov L.G. Uprochnenie i otdelka detalej poverhnostnym plasticheskim deformirovaniem [Hardening and treatment of components using surface plastic deformation]. Handbook. Moscow. Mashinostroeine Publ. 1987. 328 p. (in Russian).

thermal stratification surge line thermal fatigue thermomechanical load on-line monitoring stress-strain state