A reactor for treating a material in a medium, including a body in which is defined a reaction area capable of containing a reaction medium, at least one inlet for introducing the reaction medium into the reaction area, at least one outlet for discharging effluents out of the reaction area, characterized in that the reactor includes: - a protective casing positioned inside the body and delimiting the reaction area, the casing being spaced apart from the body so as to delimit a confinement area isolating the reaction area from the body, the reaction area and the confinement area being sealably isolated from each other, and wherein the reaction area contains a fluid medium under pressure, the confinement area containing a confinement fluid in overpressure relative to the pressure of the fluid of the reaction area; - a measuring device for measuring consumption of confinement fluid in the case of failure of the seal of the protective casing; - a pressurization capacity containing an amount of confinement fluid, the pressurization capacity being connected to the confinement area by a conduit so that the confinement area may be fed with confinement fluid; - a conduit for feeding the reaction area with reaction fluid medium; - a tapping connecting the conduit for feeding the reaction area to the pressurization capacity so as to set the confinement fluid to the pressure of the reaction fluid medium; - an anti-return valve with pressure drop being interposed between the tapping and the reaction area in order to generate a pressure difference between the pressure of the confinement fluid in the pressurization capacity and the pressure of the reaction fluid medium in the reaction area; - a measuring means measuring consumption of the confinement fluid contained in the pressurization capacity; - a heat exchanger positioned in the confinement area and integrated to a primary circuit for circulating a heat transfer fluid in order to achieve heat exchange between the heat transfer fluid flowing in the exchanger and the reaction medium contained in the reaction area; - an internal tube placed inside the protective casing and sealably attached to the body at a first end or to the protective casing, the interior volume of the sealed tube determining a central area, the tube delimiting a ring-shaped area with the protective casing, a passage for communication between the central area of the tube and the ring-shaped area being provided at a second end of the tube; and - a stirring turbine including blades stirring up the reaction medium of the central area and blades stirring up the reaction medium of the ring-shaped area. - a protective casing positioned inside the body and delimiting the reaction area, the casing being spaced apart from the body so as to delimit a confinement area isolating the reaction area from the body, the reaction area and the confinement area being sealably isolated from each other, and wherein the reaction area contains a fluid medium under pressure, the confinement area containing a confinement fluid in overpressure relative to the pressure of the fluid of the reaction area; - a measuring device for measuring consumption of confinement fluid in the case of failure of the seal of the protective casing; - a pressurization capacity containing an amount of confinement fluid, the pressurization capacity being connected to the confinement area by a conduit so that the confinement area may be fed with confinement fluid; - a conduit for feeding the reaction area with reaction fluid medium; - a tapping connecting the conduit for feeding the reaction area to the pressurization capacity so as to set the confinement fluid to the pressure of the reaction fluid medium; - an anti-return valve with pressure drop being interposed between the tapping and the reaction area in order to generate a pressure difference between the pressure of the confinement fluid in the pressurization capacity and the pressure of the reaction fluid medium in the reaction area; - a measuring means measuring consumption of the confinement fluid contained in the pressurization capacity; - a heat exchanger positioned in the confinement area and integrated to a primary circuit for circulating a heat transfer fluid in order to achieve heat exchange between the heat transfer fluid flowing in the exchanger and the reaction medium contained in the reaction area; - an internal tube placed inside the protective casing and sealably attached to the body at a first end or to the protective casing, the interior volume of the sealed tube determining a central area, the tube delimiting a ring-shaped area with the protective casing, a passage for communication between the central area of the tube and the ring-shaped area being provided at a second end of the tube; and - a stirring turbine including blades stirring up the reaction medium of the central area and blades stirring up the reaction medium of the ring-shaped area.