Izvestiya vuzov. Yadernaya Energetika

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

An experimental study into the solubility of boric acid in steam during boiling in conditions of atmospheric pressure

3/25/2019 2019 - #01 Nuclear power plants

Pityk A.V. Morozov A.V. Shlepkin A.S. Sahipgareev A.R.

DOI: https://doi.org/10.26583/npe.2019.1.03

UDC: 621.039.58:532.77

The paper presents the results of experimental studies into the solubility of boric acid in steam in conditions of atmospheric pressure in a concentration range of 16 to 240 g/kg of H2O. The problem of accumulation and crystallization of boric acid in accidents with disruption of the main circulation pipeline and the operation of passive safety systems (hydraulic accumulators of the first, second and third stages, as well as the passive heat removal system) is formulated.

An overview of the available literature data on the solubility of boric acid in steam depending on its initial concentration in solution is provided. It has been found that the available results do not cover the whole range of parameters (temperature, pressure, concentration of acid) typical of a potential emergency at an NPP with the VVER reactor. The experimental facility and the investigation procedures are described. The results of processing data obtained in the course of the experiments confirm the existing literature evidence that the change in the concentration of boric acid is described by a linear law. The application scope of the known dependence that makes it possible to calculate the solubility of H3BO3 in steam is extended to the boric acid concentration in solution of 240 g/kg which is close to the solubility of H3BO3 in water in conditions of atmospheric pressure.

The data obtained as the result of the experiments can be used for the computational simulation of emergency processes in the VVER reactor plant during operation of integrated passive safety systems such as the passive core flooding system, the passive steam generator heat removal system, and the system of stage III accumulators (HA-3 system).


  1. Kalyakin S.G., Remizov O.V., Morozov A.V., Yur’ev Yu.S., Klimanova Yu.V. Substantiation of Design Functions of the Passive Flood System for Improved NPP Project with VVER Reactor. Izvestia Vysshikh Uchebnykh Zawedeniy. Yadernaya Energetika. 2003, no. 2, pp. 94-101 (in Russian).
  2. Remizov O.V., Morozov A.V, Tsyganok A.A. Experimental Study of Non-equilibrium Thermal-hydraulic Processes in a Passive VVER Core Reflooding System. Izvestia Vysshikh Uchebnykh Zawedeniy. Yadernaya Energetika. 2009, no. 4, pp. 115-123 (in Russian).
  3. Luk’yanov A.A., Zajtsev A.A., Morozov A.V., Popova T.V., Remizov O.V., Tsyganok A.A., Kalyakin D.S. Numerical and experimental investigation of the effect of non-condensable gases on the VVER steam generator model operation in condensing mode during beyond design basis accident. Izvestia Vysshikh Uchebnykh Zawedeniy. Yadernaya Energetika. 2010, no. 4, pp. 172-182 (in Russian).
  4. Berkovich V.M., Kopytov I.I., Taranov G.S. Mal’cev M.B. Features of the design for a new generation nuclear power station equipped with a VVER-1000 reactor having enhanced safety]. Teploenergetika. 2005, no. 1, pp. 9-15 (in Russian).
  5. Shmal’ I.I. Crystallization Modeling Problems. Molodoj uchyonyj. 2013, no. 8 (55), pp. 44-47 (in Russian).
  6. Kojen P. Water Coolant Technology of Power Reactors. Moscow. Atomizdat Publ., 1973, 327 p. (in Russian).
  7. Zakutaev M.O., Bykov M.A., Zajtsev S.I., Elkin I.V., Pylev S.S., Melihov O.I., Melihov V.I., Nikonov S.M., Dorofeev D.I. The effect of the passive safety systems on the thermal state of the surface of the fuel rod imitators. Collection of research papers of the IX-th International Scientific and technical conference «Safety Assurance of NPP WWER». Podolsk. JSC EDB «Hydropress» Publ., 2015, p. 111 (in Russian).
  8. Morozov A.V., Pityk A.V., Ragulin S.V., Sakhipgareev A.R., Soshkina A.S., Shlepkin A.S. Estimation of influence of boric acid drop entrainment to its accumulation in the VVER reactor in the case of accident. Izvestiya vuzov. Yadernaya Energetika. 2017, no. 4, pp. 72-82 (in Russian).
  9. Balashov S.M., Videneev E.N., Nigmatulin B.I. The effect of the boric acid on the thermal hydraulic characteristics of the partially drained reactor core. Teploenergetika. 1992, no. 9, pp. 43-47 (in Russian).
  10. Logvinov S.A., Bezrukov Yu.A., Karetnikov G.V., Volodina N.P., Afrov A.M. The model of transport and accumulation of the boric acid in the VVER reactor in an accident with coolant leak. Proceedings of the International Conference «Thermal Physics Aspects of VVER Safety». Obninsk. FEI Publ., 1998, v. 1, pp. 47-57 (in Russian).
  11. Vaghetto R., Lee S., Hassan Y.A., Kee E. J. L. Experimental observations of boric acid precipitation scenarios. Proceedings of the International Topical Meeting on Nuclear Reactor Thermal Hydraulics 2015. NURETH-16. USA, 2015, v. 6, pp. 5263-5274.
  12. Styrikovich M.A., Tshvirashvili D.G., Nebieridze D.P. Investigations of the solubility of boric acid in saturated water vapor. Doklady AN SSSR. 1960, v. 134, no. 3, pp. 615-617 (in Russian).
  13. Tshvirashvili D.G., Galustashvili V.V. Comportment of borates and boric acid in boiling solutions. Atomnaya Energiya. 1964, v. 16, no. 1, pp. 65-67 (in Russian).
  14. Nikolaeva I.Yu., Bychkov A.Yu. Eksperimental investigations of solubility of the metaborate and sassolite in water vapor at 155°C. Vestnik Otdeleniya nauk o Zemle RAN. 2002, v. 20, no. 1, pp. 1-2 (in Russian).
  15. Nikolaeva I.Yu. Experimental study of the forms of the boron transfer under the conditions of low and medium temperature hydrothermal process. Cand. geolog. and miner. sci. diss. Moscow, 2009, 182 p. (in Russian).
  16. Nemodruk A.A., Karalova Z.K. Analytical chemistry of the boron. Moscow. Nauka Publ., 1964, 284 p. (in Russian).
  17. Tuunanen J., Tuomisto J., Raussi P. Experimental and analytical studies of boric acid concentrations in a VVER-440 reactor during the long-term cooling period of loss-of coolant accidents. Nuclear Engineering and Design. 1992, v. 148, pp. 217-231.
  18. Schmal’ I.I, Ivanov M.A. Boric acid mass transfer processes in accidental conditions. Proc. of the IXth International Scientific and technical conference «Safety Assurance of NPP VVER». Podolsk. JSC EDB «Hydropress» Publ., 2015, pp. 25-29 (in Russian).

boric acid solubility steam accumulation VVER emergency mode