[en] The azimuthal temperature gradients around the peripheral fuel pins in core subassemblies give rise to deflections of these pins, because of the differential thermal and void-swelling expansion of the cladding material. The fuel-pin deflections in the core region have a direct influence on the coolant temperature distribution which is in general in the sense of increasing the gradients thereby leading to further deflections. Whether or not this feedback process converges to a stable bowing configuration depends on the sensitivity of the deflections and of the temperature gradients to each other. This paper presents a first approach to the study of the bowing stability. The definition of two models is first required; a thermohydraulic model describing the influence of the bowing deflections on the coolant temperatures in the surrounding subchannels and the resulting changes in the azimuthal temperature gradients; a mechanical model describing the bowing response of the fuel pins to any change in the azimuthal temperature gradients. The two models are then combined in a feedback system. The results of the analysis are applied to a typical fuel subassembly and are translated into a criterion limiting the maximum allowable axial spacing between the spacer grids in the core region. (Auth.)