Activation of the Cooling Circuit Water of the Cyclone 18/9-HC Cyclotron during the Production of 18F

Resumo

Processes of accumulation of radionuclides in the cooling circuit water of the Cyclone 18/9-HC cyclotron were studied under proton irradiation of the Nirta Fluor target. It is shown that the nature of the water activation reactions in the cooling circuit and the equivalent dose rate from the equipment of the system significantly depend on the dose accumulated by the target. The main source of radionuclides in the cooling circuit water is the ¹⁶O(n,p)¹⁶N reaction. In targets with high absorbed radiation doses associated with deformation of the target entrance window, the proton-induced ¹⁴N(p,α)¹¹C and ¹⁸O(p,n)¹⁸F reactions take place. Fluoride ¹⁸F⁻, carbonate ¹¹CO₃²⁻, and hydrocarbonate H¹¹CO₃⁻ anions formed in these reactions precipitate on the ion-exchange resin during the circulation of water in the cooling circuit. It has been ascertained that the average annual radiation exposure dose for the cyclotron operator from the water activation products in the cooling circuit does not exceed 1% of the annual staff exposure limit. Recommendations are given for the application of engineering barriers in the design and reconstruction of nuclear medicine facilities for the case of water leaks from the cyclotron cooling circuit.