The value of the reactor thermal power (RTP) is used in the VVER-1000 control systems in most algorithms for generation of control, blocking and protection signals. Besides, the technical and economic indicators of the power unit are determined by this parameter. Plans to increase VVER‑1000 RTP to 101.5%, and later to 104-107% of the nominal require additional justification of the accuracy of the RTP determination. Therefore, the task of increasing the accuracy of RTP determination is important. The paper describes the ways to improve the accuracy of weighted mean thermal power (WMTP) determination by selecting the optimal weight coefficient (that subsequently is used for WMTP determination) of each of the methods of RTP determination, namely: by thermotechnical parameters of the primary and secondary sides by neutron flux in the in-core monitoring system (ICMS) and in the neutron flux control equipment (NFCE). Another possibility of increasing the accuracy of WMTP determination, namely by increasing the number of methods of RTP determination, is also considered in the paper. The analysis of changes in the background signals of self-powered neutron detectors (SPNDs) during the VVER-1000 fuel campaigns shows the fundamental possibility of using the total background signal as a separate and independent method for RTP determination. The paper presents the results of the calculation of RTP determination error taking into account the coefficients of the components of the total RTP determination error: systematic, dynamic and random errors, which must be determined during the commissioning phase. The results of reduction of the error of WMTP determination in case of application of the additional method of RTP determination based on background signals of the SPNDs are presented. Theoretically, possible minimum values of the WMTP determination error are given depending on the values of the error of the RTP determination by separate methods.
2. Dobrotvorskii, A.N. (2017). Development and substantiation of methods of determination of weighted mean power of NPP units with VVER-1000: The thesis for scientific degree of the candidate of technical sciences. Novovoronezh, 191 p.
3. Bai, V.F., Lupishko, A.N., Makarov, S.V., Bogachek, L.N. (2010). State of in-core thermal control and analysis of the main thermal and physical characteristics of RP of Kalinin NP. Book of abstracts, 7th International Scientific and Technical Conference “Safety, Effectiveness and Economics of Nuclear Power Engineering”, Moscow, 228-230.
4. Bai, V.F., Bogachek, L.N., Makarov, S.V. (2015). Influence of HPH operating modes on temperature field at the inlet of fuel assembly in the core and on thermal and physical characteristics of VVER-1000 reactor of Kalinin NPP. Book of abstracts, 9th International Scientific and Technical Conference “Safety Assurance at NPP with VVER”, Podolsk.
5. Taylor, J. (1997). An introduction to error analysis: the study of uncertainties in physical measurements. University Science Books, 2nd edition, 448.
6. Agapov, S.A., Lysenko, V.V., Musorin, A.I., Tsypin, S.G. (1991). Radiation methods for measuring VVER parameters. Energoizdat, Moscow, 129 p.
7. Lysenko, V.V., Musorin, A.I., Rymarenko, A.I., Tsypin, S.G. (1985). Determination of nuclear-physical and thermophysical characteristics of VVER using radiation meters. Energoizdat, Moscow (Rus).
8. Graham, K.F. (1977). 16N Power measuring system. Rep WCAP-9191, Westinghouse Atomic Power Division, Pittsburgh, USA.
9. DÉCOR system (1997). Direct measurement of the reactor coolant flow based on cross-correlation of Nitrogen 16 time fluctuation. Research and development division EDF preprint, Chatou, France.
10. Comanche Peak Steam Electric Station Unit 2 (1996). Unidentified overpower condition following a substantial loss of feedwater heating. WANO inf. EAR ATL 96-012.
11. Kuz’min, V.V., Bogachek, L.N., Alyev, R.R. (2015). Correlation measurements of primary coolant flow rate by 16N activity at Kalinin NPP. Book of abstracts, 9th International Scientific and Technical Conference “Safety Assurance at NPP with VVER”, Podolsk.
12. Technical report WCAP-13303 (1990), Westinghouse Atomic Power Division, Pittsburgh, USA.
13. Abdullaev, A.M., Kulish, G.V., Sleptsov, S.N., Zhukov, A.I. (2009). Influence of the guide thimble bypass flow on fuel assembly outlet temperature measurement in the VVER-1000 mixed core computational analysis. Book of abstracts, 6th International Scientific and Technical Conference “Safety Assurance at NPP with VVER”, Podolsk (Rus).
14. Goranchuk, V.V. (2019). Monitoring of VVER-1000 core by methods of neutron-noise diagnostic: The thesis for scientific degree of the candidate of technical sciences. Kyiv, 190 p. (Ukr).
15. Karasev, V.S., Ogorodnik, S.S., Coglin, Yu.L. (1970). The study of the calibration characteristics of the calorimeter in intense fields of radiation. Nuclear Energy, 29(6), 449.
16. Borysenko, V.I., Piontkovskyi, Yu.F., Goranchuk, V.V. (2016). Model of formation of in-core neutron detector signal. Nuclear Physics and Atomic Energy, Kyiv, 17(4), 364-373.
17. Saunin, Yu.V., Dobrotvorskii, A.N., Semenikhin, A.V. (2008). Methods of estimation of weight coefficient when determining weighted mean thermal power of VVER reactors. Heavy Machine Building, Moscow, 11, pp. 13-17.
18. Vorobieva, D.V., Lipin, N.V., Milto, N.V., Milto, V.A., Sakharova, T.S., Skorokhodov, D.N. (2017). Calculation of RP power based on signals from in-core detectors. Analysis of operation experience. Book of abstracts, 10th International Scientific and Technical Conference “Safety Assurance at NPP with VVER”, Podolsk.