Simulation of Processes in the Containment of the VVER‑1000 Reactor Facility During Leak Tests

A. M. Holovchenko¹, V. V. Zaporozhan², I. V. Zaporozhan¹, V. P. Kravchenko¹

¹ Odesa National Polytechnic University, 1, Shevchenko ave, Odesa, 65044, Ukraine
² Separate Subdivision “Scientific and Technical Center” of the JSC “NNEGC ‘Energoatom’”, 22–24, Hoholivska st.,  01054, Kyiv, Ukraine

DOI: doi.org/10.31717/2311-8253.23.3.1

Abstract

The last barrier to the release of radioactive elements into the environment in the event of an accident at a nuclear power plant is hermetic fencing (HF). After each scheduled preventive repair, leak tests are carried out to confirm the ability of the system to perform its functions. The tests consist of five stages (vacuuming, air injection, parameter stabilization, integral leakage measurement and pressure relief). A mathematical model of the state of the environment in the HF is developed, which consists of differential equations of energy balance, material balance and temperature change in materials of passive heat absorbers at non-stationary thermal conductivity. The model takes into account the evaporation of steam from the spent fuel pool. The system of differential equations is solved by the Runge–Kutta–Fehlberg method. The adequacy of the model was checked on the basis of comparison of the calculation results with the data of the test report of the HFS at the 4th unit of the Rivne NPP. In the process of stabilizing the parameters, the rate of temperature change almost coincides with the full-scale data. To shorten the stabilization stage, it is proposed to regulate the air temperature at the outlet of the compressor through the use of an ejector, which will suck in the required amount of ambient air with a lower temperature. It is shown that with a difference between the temperature of the discharged air and the temperature in the HF of 0.5 °C, stabilization is achieved in 30 minutes.

Keywords: hermetic fencing system, leak test, mathematical model, reduction of parameter stabilization time.

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