Catalytic reactor with radial flow of a hydrocarbon feedstock, said reactor comprising: - at least one means for introducing said feedstock to be treated; - at least one means for discharging the effluent resulting from the catalytic reaction; - a reaction zone enclosed in a substantially cylindrical outer shell that is in the form of at least one catalytic module extending along the vertical axis, said catalytic module comprising: ∘ at least one catalyst bed; ∘ at least one outer wall and one inner wall permeable respectively to the feedstock to be treated and to the effluent resulting from the catalytic reaction; ∘ at least one first side wall and one second side wall impermeable to the feedstock to be treated; - at least one means for supporting said catalytic module; - at least one means for collecting the effluent resulting from the catalytic reaction extending along the axis in communication with said outer wall or said inner wall of said catalytic module; - an annular zone located at the same level as said catalytic module, outside of the reaction zone, said catalytic reactor being characterized in that: - when said catalytic reactor comprises a single catalytic module, said reactor comprises an empty space located outside of the reaction zone, between the first side wall and the second side wall of said catalytic module, and opening onto said annular zone, - when said catalytic reactor comprises a plurality of catalytic modules, said reactor comprises at least one empty space located outside of the reaction zone, between the first side wall of a first catalytic module and the second side wall of a second catalytic module adjacent to the first catalytic module, and opening onto said annular zone, said empty space comprising at least one solid net extending along the vertical axis and positioned adjacent to the collecting means. - at least one means for introducing said feedstock to be treated; - at least one means for discharging the effluent resulting from the catalytic reaction; - a reaction zone enclosed in a substantially cylindrical outer shell that is in the form of at least one catalytic module extending along the vertical axis, said catalytic module comprising: ∘ at least one catalyst bed; ∘ at least one outer wall and one inner wall permeable respectively to the feedstock to be treated and to the effluent resulting from the catalytic reaction; ∘ at least one first side wall and one second side wall impermeable to the feedstock to be treated; ∘ at least one catalyst bed; ∘ at least one outer wall and one inner wall permeable respectively to the feedstock to be treated and to the effluent resulting from the catalytic reaction; ∘ at least one first side wall and one second side wall impermeable to the feedstock to be treated; - at least one means for supporting said catalytic module; - at least one means for collecting the effluent resulting from the catalytic reaction extending along the axis in communication with said outer wall or said inner wall of said catalytic module; - an annular zone located at the same level as said catalytic module, outside of the reaction zone, - when said catalytic reactor comprises a single catalytic module, said reactor comprises an empty space located outside of the reaction zone, between the first side wall and the second side wall of said catalytic module, and opening onto said annular zone, - when said catalytic reactor comprises a plurality of catalytic modules, said reactor comprises at least one empty space located outside of the reaction zone, between the first side wall of a first catalytic module and the second side wall of a second catalytic module adjacent to the first catalytic module, and opening onto said annular zone,