# Justification of the Safe Distance between the Safety Channel Cables of Nuclear Power Plants with Pressurized Water Reactors located in the Same Fire Zone

Annotation:

Currently, there are no methods of mathematical modeling of the operability of power and signal cables used at the nuclear power plants in real and standard fire conditions, including the use of intumescent flame retardants. The purpose of the article is a theoretical assessment of the safe distance between the cables of the safety channels of nuclear power plants with pressurized water reactors located in the same fire zone. To achieve it, the time of occurrence of a short circuit in the cables of the channels of safety systems from the beginning of a real fire and depending on the distance between adjacent cable lines was estimated. An integral method of mathematical modeling of the development of a fire in a room is used. To determine the temperature distribution inside the cable insulation, the thermal conductivity equation is solved. The analysis of the obtained results is carried out. The calculation results made it possible to formulate the requirements for the swelling temperature of fire retardant compounds for treating the outer surfaces of SB cables: the above temperature should be no more than 150 °C for the flame retardant cables, and 180 °C for the non-flame retardant cables, as well as at distances between open cables of two safety systems smaller than 2, the outer surfaces of the safety cables must be treated with a fire retardant compound with a fire retardant efficiency of at least 120 minutes. The conducted theoretical assessment of the safe distance between the cables of the safety channels of nuclear power plants with pressurized water reactors located in the same fire zone, using the proposed mathematical model, showed that in a real fire, in order to prevent a short circuit in the cables of the safety systems, as well as ignition of the insulation of adjacent cables, it is required to justify safe distances between the adjacent cables of the safety system of nuclear power plants, taking into account the specific dimensions of the premises and the properties of the cable insulation material and the fire-retardant coatings used.

References:
1. Lebedchenko O.S., Zykov V.I., Puzach S.V. Assessment of operation of safety channel signal cables at nuclear power plants under fire conditions. Pozharovzryvobezopasnost = Fire and Explosion Safety. 2020. Vol. 29. № 4. pp. 51–58. (In Russ.).
2. Huang Xianjia, Wang Yuhong, Zeng Wuyong, Peng Lan, Cheng A.C.H., Chow W.K. Compartment temperature estimation of a multiple-layer cable tray fire with different cable arrangements in a closed compartment. Journal of Fire Sciences. 2019. Vol. 37. Iss. 4–6. DOI: 10.1177/0734904119860410
3. Tiranovskiy G.G. Installation of automatic fire extinguishing in the cable structures of energy facilities. Мoscow: Energoizdat, 1982. 64 p. (In Russ.).
4. IAEA-TECDOC-1825. Benchmark Analysis for Condition Monitoring Test Techniques of Aged Low Voltage Cables in Nuclear Power Plants. Final Results of a Coordinated Research Project. Available at: https://www.iaea.org/publications/11164/benchmark-analysis-for-condition-monitoring-test-techniques-of-aged-low-voltage-cables-in-nuclear-power-plants (accessed: October 10, 2023).
5. Csanyi E. Internal electrical systems within nuclear power plant stations (power sources). Available at: https://electrical-engineering-portal.com/electrical-systems-nuclear-power-plant-stations (accessed: October 10, 2023).
6. Pena G., Gelbard F., Brown J.R., Bernstein R. Neely, Jason C., Glover S.F., Zutavern F.J., Williamson K. M., Von White G. Submerged Medium Voltage Cable Systems at Nuclear Power Plants: A Review of Research Efforts Relevant to Ageing Mechanisms and Condition Monitoring. Rockville: U.S. Nuclear Regulatory Commission; Oak Ridge: Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2015. DOI: 10.2172/1177756
7. Babrauskas V., Peacock R., Braun E., Bukowski R., Jones W. Fire Performance of Wire and Cable: Reaction-to-Fire Tests — A Critical Review of the Existing Methods and of New Concepts (NIST TN 1219). Available at: https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=912941 (accessed: October 10, 2023).
8. Puzach S.V., Lebedchenko O.S., Sizukhin S.V. Substantiating passive fire protection technology for the main buildings of nuclear power plants with water-cooled reactors based on calculating fire resistance of enclosing structures. Pozhary i chrezvychaynye situatsii: predotvrashchenie, likvidatsiya = Fires and Emergencies: Prevention, Elimination. 2020. № 1. pp. 22–29. (In Russ.). DOI: 10.25257/FE.2020.1.22-29
9. Koshmarov Yu.A. Prediction of hzardous factors of fire in the premises: textbook. Мoscow: Akademiya GPS MVD Rossii, 2000. 118 p. (In Russ.).
10. Drayzdeyl D. Introduction to fire dynamics. Мoscow: Stroyizdat, 1990. 424 p. (In Russ.).
11. Patankar S. Numerical heat transfer and fluid flow. Мoscow: Energoatomizdat, 1984. 152 p. (In Russ.).
12. Kireev A.A., Karakulin A.B., Zhernoklev K.V. Experimental determination of the mass rate of rubber burnout: collection of scientific papers. Kharkiv: NUGZU, 2014. Iss. 35. 213 p. (In Russ.).
13. Cable Ageing in Nuclear Power Plants. Report on the first and second terms (2012–2017) of the NEA Cable Ageing Data and Knowledge (CADAK) Project. Available at: https://one.oecd.org/document/NEA/CSNI/R(2018)8/en/pdf (accessed: October 10, 2023).
14. Puzach S.V., Lebedchenko O.S., Zykov V.I., Chistyakov T.I. Operability evaluation of electrical wires and cables subjected to simultaneous fire and current loadings. Pozharovzryvobezopasnost = Fire and Explosion Safety. 2022. Vol. 31. № 6. pp. 56–67. (In Russ.). DOI: 10.22227/0869-7493.2022.31.06.56-67
DOI: 10.24000/0409-2961-2024-1-68-73
Year: 2024
Issue num: January
Keywords : cable fire zone nuclear power plants safety channel short circuit thermal destruction of insulation intumescent fire retardant composition intumescent temperature pressurized water reactor
Authors:
;
• Lebedchenko O.S.
Cand. Sci. (Legal), Assoc. Prof., ol-26@mail.ru, Academy of GPS of the Ministry of Emergency Situations of Russia, Moscow, Russian Federation