A reactor for the hydrothermal oxidation treatment of an organic material in a reaction medium, the reactor comprising: - an enclosure delimiting a cavity in which is housed a confinement member defining an internal zone, called a confinement zone, for containing the reaction medium, and an external zone, called a peripheral zone; - at least one oxidizing fluid inlet for introducing an oxidizing fluid into the peripheral zone; - at least one first cooling system configured to cool the oxidizing fluid at the oxidizing fluid inlet in a first portion of the peripheral zone, so as to define a cold peripheral zone; - at least one heating system (Q5-Q5') for heating the oxidizing fluid in a second portion of the peripheral zone, prior to its introduction into the confinement zone, so as to define a hot peripheral zone; and - at least one introduction channel for the organic material into the confinement zone for introducing a loaded fluid, comprising the organic material and water, said introduction channel being provided with an introduction mouthpiece through which the loaded fluid is introduced into the introduction channel; - an outlet from the confinement zone for discharging effluents produced in the confinement zone out of the enclosure; the confinement zone and the peripheral zone being in fluid communication via at least one opening arranged in the end of the confinement member located in the hot peripheral area; the reactor being characterized in that it further comprises: - a stirring system (56; 54) of the introduction channel adapted to create turbulence in the fluid loaded in said introduction channel; - at least one second cooling system adapted to create, in the loaded fluid, a temperature gradient along the introduction channel between a so-called cold temperature, lower than a reaction temperature prevailing in the confinement zone, and the reaction temperature; and the reactor being characterized in that the first cooling system (Q6-Q6') is an outer circulation cold loop having a fluid inlet (Q6') and a fluid outlet opening into the cold peripheral zone, and the heating system (Q5-Q5') is an outer circulation hot loop having a fluid inlet (Q5') and a fluid outlet opening into the hot peripheral zone, each circulation loop being equipped with a circulator (31; 32) and a heat exchanger (30; 33), and having as a coolant the oxidizing fluid circulating in the peripheral zone, an element being placed in the peripheral zone to separate the cold and hot loops, while allowing the oxidizing fluid to pass from the cold peripheral zone to the hot peripheral zone. - an enclosure delimiting a cavity in which is housed a confinement member defining an internal zone, called a confinement zone, for containing the reaction medium, and an external zone, called a peripheral zone; - at least one oxidizing fluid inlet for introducing an oxidizing fluid into the peripheral zone; - at least one first cooling system configured to cool the oxidizing fluid at the oxidizing fluid inlet in a first portion of the peripheral zone, so as to define a cold peripheral zone; - at least one heating system (Q5-Q5') for heating the oxidizing fluid in a second portion of the peripheral zone, prior to its introduction into the confinement zone, so as to define a hot peripheral zone; and - at least one introduction channel for the organic material into the confinement zone for introducing a loaded fluid, comprising the organic material and water, said introduction channel being provided with an introduction mouthpiece through which the loaded fluid is introduced into the introduction channel; - an outlet from the confinement zone for discharging effluents produced in the confinement zone out of the enclosure; the confinement zone and the peripheral zone being in fluid communication via at least one opening arranged in the end of the confinement member located in the hot peripheral area; the reactor being characterized in that it further comprises: - a stirring system (56; 54) of the introduction channel adapted to create turbulence in the fluid loaded in said introduction channel; - at least one second cooling system adapted to create, in the loaded fluid, a temperature gradient along the introduction channel between a so-called cold temperature, lower than a reaction temperature prevailing in the confinement zone, and the reaction temperature; - a stirring system (56; 54) of the introduction channel adapted to create turbulence in the fluid loaded in said introduction channel; - at least one second cooling system adapted to create, in the loaded fluid, a temperature gradient along the introduction channel between a so-called cold temperature, lower than a reaction temperature prevailing in the confinement zone, and the reaction temperature; and the reactor being characterized in that the first cooling system (Q6-Q6') is an outer circulation cold loop having a fluid inlet (Q6') and a fluid outlet opening into the cold peripheral zone, and the heating system (Q5-Q5') is an outer circulation hot loop having a fluid inlet (Q5') and a fluid outlet opening into the hot peripheral zone, each circulation loop being equipped with a circulator (31; 32) and a heat exchanger (30; 33), and having as a coolant the oxidizing fluid circulating in the peripheral zone, an element being placed in the peripheral zone to separate the cold and hot loops, while allowing the oxidizing fluid to pass from the cold peripheral zone to the hot peripheral zone.