Study of WWER Reactors Neutronic Noise Spectral Images in Irregular Thermоhydraulic Regimes of Core Zones

І. G. Sharaevsky, Т. S. Vlasenko, L. B. Zimin,
А. V. Nоsоvskyi, N. М. Fіаlkо, G. І. Sharaevsky

Institute for Safety Problems of Nuclear Power Plants,
NAS of Ukraine, 12, Lysogirska st., Kyiv, 03028, Ukraine

DOI: doi.org/10.31717/2311-8253.22.1.2

Abstract

The information on the peculiarities of the manifestations of potentially dangerous thermohydraulic anomalies, that occur unpredictably during the operation of the WWER reactor core, is generalized. Considerable attention is paid to the threat of uncontrolled occurrence of latent pre-emergency and emergency operating states in fuel assemblies during the generation of the vapor phase on the surface of fuel elements, including the heat transfer
crisis with subsequent boiling of the coolant. It is noted that under these conditions, heat transfer, which should occur exclusively in the convective mode, is also characterized by the uncontrolled occurrence of the boiling process, from the activation of the first centers of vaporization to the formation of a developed bubble structure of the coolant. The limited possibilities of modern technical means of monitoring the technical condition of WWER, which do not provide detection of these anomalies and preemergency heat transfer regimes, are considered. Given the data on neutron flux fluctuations, it is shown that the noise components at the output of standard electron emission neutron flux meters carry important diagnostic information on thermohydraulic processes in the volume of the core, which is currently lost. With this in mind, it is concluded that it is necessary to immediately develop a methodology for the operational identification of random spectral realizations of neutron noise, which is registered at the outputs of neutron detectors of existing in-reactor control systems. The nature of the necessary reliable data on the spectral structure of the main types of diagnostic images (signatures or patterns) of neutron noise, which is registered at the output of standard neutron flux detectors in accordance with the main types of thermohydraulic anomalies, is determined. The analysis of known data and performed with the participation of authors of reactor experiments on the basis of which it is proved that the spectral structure of auto- and coherent signal density at the output of standard neutron flux detectors contains comprehensive diagnostic information on the type and location of vapor-liquid structures of WWER reactor core. With this in mind, the information characteristics of individual spectral ranges of neutron noise are analyzed and conclusions are made about their direct correspondence to the characteristic thermohydraulic processes as objects of diagnostics.

Keywords: WWER, core, neutron noise, spectral characteristics of signals, thermohydraulic anomalies, diagnostics.

References

1. Samoilov О. B., Usynin G. B., Bakhmet’ev А. М. (1989). Bezopasnost’ jadernykh energeticheskikh ustanovok [Safety of nuclear power plants]. Мoscow: Energoatomizdat, 279 p. (in Rus.)

2. Klyuchnikov A. A., Sharaevsky I. G., Fialko N. M., Zimin L. B., Sharaevsky G. I. (2010). Teplofizika bezopas‑ nosti atomnykh elektrostantsiy [Thermal physics of nuclear power plants safety]. Chornobyl: ISP NPP, NAS of Ukraine, 484 p. (in Rus.)

3. Klyuchnikov  А.  А., Sharaevsky  I.  G., Fialko  N.  M., Zimin L. B., Sharaevskaya N. I. (2013). Teplofizika povrezh‑ denij reaktornykh ustanovok [Thermophysics of NPP damages]. Kyiv: ISP NPP, NAS of Ukraine, 528 p. (in Rus.)

4. Sharevsky І. G. (2010) Rozpiznavannia peredavarijnykh teplogydravlichykh procesiv u vodookholodzhuvanykh jadernykh energenychnykh reactorakh [Recognition of pre-emergency thermohydraulic processes in water- cooled nuclear power reactors] (PhD thesis). Кyiv: ISP NPP, NAS of Ukraine, 48 р. (in Ukr.) 5. Sharaevsky І. G., Fіаlkо N. М., Nоsоvskyi А. V., Zimin L. B., Vlasenko Т. S., Sharaevsky G. І. (2020). World trends of construction development of water- cooled supercritical pressure reactors. Nuclear Power and the Environment, vol. 17, no. 2, pp. 3–15. doi.org/10.31717/2311-8253.20.2.1. (in Ukr.)

6. Sharaevsky  І.  G., Fіаlkо  N.  М., Nоsоvskyi  А.  V., Zimin L. B., Vlasenko Т. S., Sharaevsky G. І. (2020). Main directions of Russian developments of prospective structures of water- cooled supercritical pressure reactors. Nu‑ clear Power and the Environment, vol. 18, no. 3, pp. 34–41. doi.org/10.31717/2311-8253.20.3.4. (in Ukr.)

7. Abdelmessih A. H., Yin S. T. (1976). An experimental investigation on incipient boiling oscillation of Freon-11 in forced convection. Proceedings of the Two‑ Phase Flow and Heat Transfer Symposium — Workshop (Fort Lander‑ dale, Fl.), pp. 203–204.

8. Rassokhin N. G., Gradusov G. N., Gumileva M. G. (1975). [Features of influence of the heat carrier with high temperature on a heat-transfer surface from aluminum alloys at various types of heat exchange]. Proc. МEI, vol. 257, pp. 81–87. (in Rus.)

9. Kashinskyi V. I., Nevstrueva Е. I., Romanovskyi I. М. (1977). [Influence of deposition of corrosion products on the temperature regime of pipes at the developed boiling]. In: Crizisy kipeniya i okolocriticheskaya oblast’ [Heat transfer crises and near-critical ares]. Leningrad: Nauka, pp. 189–196. (in Rus.)

10. Sharaevsky І. G., Vlasenko Т. S., Zimin L. B., Nоsоvskyi А. V., Fіаlkо N. М., Sharaevsky G. І. (2021). Problems of abnormal dynamics of thermal hydraulic processes in prospective reactors with supercritical parameters of light water coolant.
Nuclear Power and the Environment, vol. 21, no. 2, pp. 3–16. doi.org/10.31717/2311–8253.21.2.1. (in Ukr.)

11. Kozma R., van Dam N., Hoogenboom I. E. (1992). Identification of flow patterns by neutron noi. Analysis during actual coolant boiling in thin rectangular channels. Nucl. Technology, vol. 100, pp. 97–109.

12. Birger I. А. (1978). Tekhnicheskaya diagnostika [Technical diagnostics]. Мoscow: Маshinostroenie, 239 p. (in Rus.)

13. Verkhagen K., Jeik R., Grun F., Josten J., Verbek P.; Curevich I. B. (ed.) (1985). Raspoznavanie obrazov. Sostojanie i perspektivy [Pattern recognition. State and prospects.]. Translated from English. Мoscow: Radio i svjaz’, 103 p. (in Rus.)

14. Integrated system for operational technical diagnostics of a NPP power unit with a VVER-1000 reactor. Теchical Project. Kharkiv: JSC “Khartron”, “Khartron- АRKOS”, 1996, 269 p. (in Rus.)

15. Monitoring, control and diagnostic system (MCDS) of a re‑ actor plant with a V‑320 reactor. Data sheet. — Мoscow: NRC “Kurchatov Institute”, Institute of Nuclear Reactors, 1995, 95 р. (in Rus.)

16. Report on the results of the first months of operation of the reactor noise diagnostics system. Udomlya: Kalinin NPP, 1992, 37 p. (in Rus.)

17. Shulz I. (1997). Novye razvitiya v oblasti tekhnicheskoi diag‑ nostiki dlia AES s VVER na osnove sovremennykh EVM tipa PC [New developments in the field of technical diagnostics for NPPs with VVER based on modern computers of the RS type]. Siemens AG — Bereich Energiezengung (KWU/ S42), 26 p. (in Rus.)

18. Blumentritt G., Liewers P., Rindelhardt U., Werner M. (1990). Rauschdiagnostische Untersuchungen zum Kuhlmittelsieden in Druckwasserreaktoren. Kernergie, no. 1, pp. 260–274.

19. Prokop K., Novak M. (1981). Zkuscnosti z vyvoje, projktovani a puuziti diagnostickehe systemu v obdobi spousteni a v provozu JE. Energetica, vol. 31, no. 10, pp. 429–434. (in Cze)

20. Nosovskyi  A.  V., Sharaevsky  I.  G., Fialko  N.  M., Zimin L. B., Sharaevsky G. I. (2017). Teplofizika resursa jadernykh energoustanovok [Thermal physics of NPP resource]. Kyiv: ISP NPP, NAS of Ukraine, 624 p. (in Rus.)

Full Text (PDF)