PSI - Issue 73

Juraj Králik et al. / Procedia Structural Integrity 73 (2025) 73–80 Juraj Králik/ Structural Integrity Procedia 00 (2025) 000–000

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1. Introduction This paper deals with the experimental and numerical analysis of the extreme wind impact on the NPP structures and ventilation chimney. The NPP buildings with the reactor VVER 440/213 consist the turbine hall, middle building, reactor building and bubble condenser (Fig. 1). This chimney is situated in NPP buildings and the real wind loads is different than it is defined in Eurocode requirements. The international organization IAEA in Vienna (2003) set up the design requirements for the safety and reliability of the NPP structures. The extreme environmental events (e.g., wind, temperature, snow, explosion...) are the important loads from the point of the NPP safety performance [ NUREG-1150 (1990), NUREG/CR-4839 (1992), IAEA in Vienna (2003), NRA SR (2011), Králik (2009) ] . The extreme wind loads are defined with the probability of mean return period equal to one per 10 4 years. Nuclear Regulatory Authority of the Slovakia [NRA SR (2011)] published a set of the regulatory guide to the risk analysis of NPP. The extreme wind load was defined by the results of scientific research SHMU (2012). The following physical quantities are used in this paper:

Nomenclature c pe

external wind parameters

air density [ kg/m 3 ] air velocity [m/s]

ρ

model constant

C µ

v

relative turbulent dissipation kinetic energy of turbulence Von-Karman constant dissipation parameter

reference air velocity [m/s] basic wind pressure [Pa] reference height [m] terrain roughness [m]

v ref w b z ref

ε

k κ

ω

z o

differential pressure

p

2. Experimental analysis of extreme wind impact The wind tunnel of STU Bratislava was used for the analysis of the extreme wind impact to the NPP buildings in Hubova (2020). In the experimental measurements of external wind parameters c pe , we also considered objects that were at a distance of 300m, as shown in Fig.1. Two types of terrain have also been taken into account, where for flows from north to east to southern flows pass through the fields and smoother terrain categories II and from the south through the western flow to the northwest flow passes through category III, where there are also other objects that partially stop or modify the flow.

Fig. 1. Experimental model: a) 3D NPP model, b) Wind flow orientation.