[en] A system for the irradiation of water was developed at the CV-28 compact cyclotron of IPEN-CNEN/SP. This system was tested and its viability verified with the irradiation of circulating water (+- 66 ml) and the radioisotope produced this way was ¹⁸F. The ¹⁸F is a radioisotope that can be used in the diagnosis of brain and heart diseases, through the PET technique (Positron Emission Tomography). The whole irradiation system is automatically controlled by means of a panel specially designed for this purpose. The chemical separation of ¹⁸F after the irradiation was carried out using an Anionic Exchange Resin DOWEX 1X8 (100-200 mesh) and Potassium Carbonate as elutant. The ¹⁸F was obtained in aqueous solution in the chemical form of Fluoride (F), with maximum retention of 100 % . The maximum elution yield obtained was 86 %. The minimum specific activity obtained was 6.623 X 10⁵ MBq/mmol. The production yields obtained were, on average, (4.81 +- 0.42) MBq/mu A.h. The limit of current tested was 34 mu A, with water temperature of 71 deg C in the exit of target-holder. The maximum length of the irradiation was 2 hours. The windows of aluminium and silver tested behaved on a safe way, as well as the two cooling systems: BAR (Cooling Water Pump) and independent. Heat transfer calculations were made concerning the water that was being irradiated, and the results (author)